Difference between revisions of "751.1 Preliminary Design"

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|'''Forms'''
 
|'''Forms'''
 
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|[http://epg.modot.mo.gov/forms/DE-Bridge/Structural%20Rehabilitation%20Checklist.xlt Structural Rehabilitation Checklist]
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|[[media:751.1.3.2_Structural_Rehabilitation_Checklist.xlsm|Structural Rehabilitation Checklist]]
 
|}
 
|}
  
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===751.1.1.1 Introduction===
 
===751.1.1.1 Introduction===
  
The Preliminary Design of a structure begins with the district submitting a Bridge Survey and Preliminary Geotechnical Report indicating their need for a structure, and ends with the completion of the Design Layout or TS&L submittal (type, size and location).  This section is intended to be a guide for those individuals assigned the task of performing the Preliminary Design or “laying out” of a structure.
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The Preliminary Design of a structure begins with the district submitting a Bridge Survey indicating their need for a structure, and ends with the completion of the Substructure Layout or TS&L submittal (type, size and location).  This article is intended to be a guide for those individuals assigned the task of performing the Preliminary Design or “laying out” of a structure.
  
 
The types of structures can be broken into five categories:
 
The types of structures can be broken into five categories:
:1.) Bridge Over Water
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:1.) Bridge over Water
:2.) Bridge Over Roadway or Railroad
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:2.) Bridge over Roadway or Railroad
:3.) Box Culvert Over Water
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:3.) Box Culvert over Water
:4.) Retaining Wall
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:4.) Retaining Wall (CIP walls taller than 5 ft., MSE walls adjacent to bridge end bents)
:5.) Rehabilitation or Overlay of Existing Structure
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:5.) Rehabilitation or Modification  of Existing Structure
  
 
In addition to the following information, the Preliminary Design shall consider hydraulic issues where applicable.
 
In addition to the following information, the Preliminary Design shall consider hydraulic issues where applicable.
  
===751.1.1.2 Bridge Survey===
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===751.1.1.2 Bridge Survey Processing and Bridge Numbering===
  
The Preliminary Design process starts with the receipt of the Bridge Survey. The Structural Resource Manager records the receipt date in his file and then passes the Bridge Survey on to the Bridge Survey Processor.  The following is a list of steps that are taken by the Bridge Survey Processor.   
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The Preliminary Design process starts with the receipt of the Bridge Survey. The following is a list of steps that are taken by the Bridge Survey Processor.   
  
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'''Assign a Bridge Number to the Structure'''
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The Bridge Division assigns bridge numbers in Bloodhound to all new, rehabilitated or modified structures  (i.e., bridges, box culverts (see [[750.7 Non-Hydraulic Considerations#750.7.4.3 Summary of Responsibilities|EPG 750.7.4.3 Summary of Responsibilities]]), CIP retaining walls over 5 ft. tall and MSE walls adjacent to bridge end bents).
  
'''Assign a Bridge Number to the Structure'''
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Enter the Bridge Number, survey received date and feature crossed in the Bloodhound database.
  
Use the next number in the Bridge Index.  Book 1 is for bridge numbers that start with an “A” thru A9999 then with a “B” starting at B0001, while book 2 is for all other state bridge numbers.  The “UIP” book is for off-system bridges.  Anytime a bridge is rehabilitated or changed in any way, it will receive a new bridge number.  For example, bridge no. A-1234 would become A12341 for the first rehab. And A12342 for the second rehab.  Another example is that bridge no. L-123R would become L01232 for its next rehab.  New timber bridges start with the letter “T” in book 2.
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'''New Structures:'''
  
Enter the Bridge No. and other required information in the Bridge Survey Book.
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:New structures are numbered in ascending order using the next available bridge number. Numbering for new structures (except timber structures) start at A0001 thru A9999 and will be followed by B1000 thru B9999. (Note: B0001 thru B0581 were used for the Safe and Sound Bridge Replacement Program.)
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:New timber bridges are numbered in the same manner using the letter “T” instead of the letter “A”.
  
Enter the Bridge No. in the Survey Received database – Microsoft Access (J:\Brhist\survrec.mdb) The password required to do this is available from the Office clerk.
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'''Temporary Structures:'''
  
Enter the Bridge No., survey received date and feature crossed in the Bloodhound 2000 database – Access
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:Temporary bridges use the same number as the new bridge with the letter “T” added to the end (i.e., the temporary bridge for A8650 would be A8650T).
  
(T:\br-proj\bloodhound2000\bloodhound-2000.mdb).
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'''Rehabilitated or Modified Structures''' (Except when rehabilitation is only for structural steel coating):
  
Write Bridge No. on the plat and profile sheets as well as the cover letter from the district.
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:'''Single Structures (Includes twin structures with individual bridge numbers): '''
  
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::Structures without a suffix letter on the existing bridge number will be numbered using the existing bridge number and a suffix number added that corresponds to the number of rehabilitations or modifications to the structure (i.e., bridge number A0455 becomes A04551 upon its first rehabilitation or modification and A04552 upon its second).
  
'''Create Job Folders'''
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:'''Single Structures with the Suffix “R”:'''
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::Structures that have the suffix “R” on the bridge number are usually bridges that have been rehabilitated or modified in the past, but in some cases bridges were given the suffix “R” to denote it as a replacement for a bridge with the same number. Review the existing bridge plans to determine if the “R” was for a rehabilitation or replacement. Structures that have been previously rehabilitated should replace the “R” with a suffix number corresponding to the total number of rehabilitations to the structure (i.e., bridge number A0444R would become A04442 (second rehab. or mod.), bridge number A0055R2 would become A00553 (third rehab. or mod.), etc.). For structures where the “R” denotes it as a replacement, the suffix number corresponds to the number of rehabilitations or modifications and the “R” is dropped (i.e., bridge number L0428R becomes L04281 for the first rehabilitation). If the “R” suffix was removed in a previous rehabilitation, the next suffix number is used regardless if the original structure was a rehabilitation or replacement.
  
Check to see if a Correspondence File has been created.  If the Correspondence File has been created, record the Bridge No. and make a Design Layout File for each structure received. If the Correspondence File has not been created, make a Correspondence File, an outer folder and a Design Layout File for each structure received.  Here is the information for each type of folder/file:
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:'''Twin Structures with the Same Bridge Number:'''
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::Twin structures with the same bridge number will use a different suffix number for each structure. The numbering is similar to a single structure with the lower suffix number being used on the eastbound or southbound structure and the next suffix number being used on the westbound or northbound structure (i.e., bridge number A0144 would become A01441 for the eastbound bridge and A01442 for the westbound bridge. A future rehabilitation would become A01443 for the eastbound bridge and A01444 for the westbound bridge). Twin bridges with an “R” suffix on the bridge number would receive the suffix numbers using the same rules, but with the same consideration given to the “R” as it is for a single structure.  
{|
 
|-
 
|style="border-bottom:2px solid black;" width="125px"|Folder Type||style="border-bottom:2px solid black;"|Required Information on Folder
 
|-
 
|Outer (pink label)||County, Route and Job No.
 
|-
 
|Correspondence||County, Route and Job No.
 
|-
 
|Design Layout||County, Route, Bridge No., Location and Job No.
 
|}
 
  
Also be sure to notify the Structural Resource Manager and appropriate Structural Project Manager (SPM) or Structural Liaison Engineer when a new Correspondence File is created.  Include in your note Job No., County, Route, Bridge No. and the Bridge Division contact.
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'''Structural Steel Coating (Use when all bridge pay items are related to structural steel coatings):'''
  
The Bridge Division contact is either the Structural Project Manager (SPM) or Structural Liaison Engineer.
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:Rehabilitations that consist only of structural steel coatings use the existing bridge number plus the suffix “-Paint” (i.e., bridge number A2100 would become A2100-Paint and bridge number A150010 (multiple rehabilitations) would become A150010-Paint). A future rehabilitation consisting of only structural steel coatings would use the suffix “-Paint2” only if no other rehabilitations have been completed since the previous coating rehabilitation. 
  
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'''Removal of Existing Bridge Structures:'''
  
'''Fill Out Bridge Survey Report (BR 105R)'''
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:When a bridge structure is removed and not replaced by a new bridge structure or is removed under a separate contract, the suffix “-Remove” should be added to the latest bridge number (i.e., bridge number T0415 would become T0415-Remove and bridge number K01651 would become K01651-Remove).
  
If the district did not include a completed form [[Media:Bridge Survey Report Form.doc|BR 105R]] for the structure, one should be completed by the Bridge Division.  This form is not necessary on rehabs, overlays and retaining walls.
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'''Re-using Bridge Numbers:'''
  
An [[Media:Bridge Survey Memo.doc|acknowledgement letter]] shall be sent to the district informing them that Bridge Division received the Bridge Survey.  Include the Bridge No. and the name of the Bridge Division contact.
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:Bridge numbers that were assigned to new structures that were never built are only reused if the proposed structure is at the same crossing location that the bridge number was originally assigned to.  
  
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:Bridge numbers that were assigned to rehabilitate or modify structures where the work was not completed may reuse the previous bridge number by adding the suffix “-#2” to the bridge number (i.e., bridge number A6545 had plans developed for deck repairs and was assigned the bridge number A65451, but the work was never completed. At a later date, bridge A6545 is set up to be redecked; the bridge number assigned to the redeck would be A65451-#2). This suffix is only recorded in Bloodhound for tracking purposes and is not shown as part of the bridge number on file folders or final plans.
  
'''Locate the Structure on the County Map'''
 
  
Pull out the map for the county this particular structure is in, circle the location and write the Bridge No. on the map (Bridges only, not walls and culverts).
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'''Create Job Folders'''
  
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Check to see if a Correspondence File has been created. If the Correspondence File has been created, record the Bridge Number(s) in Bloodhound and make a Preliminary Design File for each structure received. If the Correspondence File has not been created, make a Correspondence File, an outer folder and a Preliminary Design File for each structure received. Here is the information for each type of folder/file:
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<center>
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{|
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|-
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|style="border-bottom:2px solid black;" width="125px"|Folder Type|| ||style="border-bottom:2px solid black;"|Required Information on Folder
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|-
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|Outer (pink label)|| ||County, Route and Job No.
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|-
 +
|Correspondence|| ||County, Route and Job No.
 +
|-
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|Preliminary Design|| ||County, Route, Bridge No., Location and Job No.
 +
|}
 +
</center>
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Also, be sure to notify by email the Structural Resource Manager and the appropriate Structural Project Manager or Structural Liaison Engineer, if known, when a new Correspondence File is created. The email subject line should include the Job No., County, Route and Bridge No. Include the name of the Bridge Division contact in the email, either the Structural Project Manager or the Structural Liaison Engineer.
  
 
'''Calculate Drainage Information'''
 
'''Calculate Drainage Information'''
  
For structures over streams or waterways, calculate the drainage area, length of stream, 10% elevation, 85% elevation and slope from topographic maps.  Record this information on Form BR 105R in the Design Layout folder. If the district’s calculations indicate that the drainage area is less than 1.5 sq. miles, do not calculate the drainage area. The accuracy of the drainage area should be to the nearest 0.10 sq. mile for drainage areas less than 10 sq. miles and to the nearest 1.0 sq. mile for drainage areas greater than or equal to 10 sq. miles.
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For structures over streams or waterways, calculate the drainage area and length of stream. Generate a drainage summary and include this information along with a map showing the drainage area for the structure and the area surrounding it in the Preliminary Design folder. If the drainage area is less than 1.5 sq. miles, consult the Structural Resource Manager to determine if preliminary design by the Bridge Division is necessary. The accuracy of the drainage area should be to the nearest 0.1 sq. mile for drainage areas less than 10 sq. miles and to the nearest 1 sq. mile for drainage areas greater than or equal to 10 sq. miles. When another stream intersects the subject stream near the downstream side of the proposed structure, create a separate drainage summary for the intersecting stream and include it in the Preliminary Design folder. 
 
 
  
 
'''Process Electronic Files'''
 
'''Process Electronic Files'''
  
If electronic files of the Bridge Survey plat and profile sheets were not included, contact the Transportation Project Manager (TPM) in the district or the Roadway Consultant to arrange for the files to be sent. Consult with the SPM or Bloodhound 2000 to determine who the district TPM is. When the electronic files are received, verify that the scale is 1”=10’ and that the necessary reference files are included.  The Bridge Survey Processor may have to work with the district to correct any errors.
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When the electronic files listed in [[:Category:747 Bridge Reports and Layouts#747.1.2 Bridge Survey Submittals|EPG 747.1.2 Bridge Survey Submittals]] are received, verify that the drawing scales are correct and that the necessary reference files are included. Also, review all Bridge Survey Sheets and the Bridge Survey Checklist for accuracy and completeness.  The Bridge Survey Processor may have to work with the district to correct any discrepancies and/or omissions.  
  
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Add the newly assigned bridge number to the files and place a hard copy in the layout folder.
 
 
 
'''Final Step for Bridge Survey Processor'''
 
'''Final Step for Bridge Survey Processor'''
  
Once all of these steps are completed, the Bridge Survey Processor should deliver the Correspondence File, outer folder and the Design Layout Folder to the Structural Resource Manager. The Structural Resource Manager will then pass the files to the SPM. The SPM then requests the Structural Resource Manager to assign a Preliminary Designer.
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Once all of these steps are completed, the Bridge Survey Processor should deliver the Correspondence File, outer folder and the Preliminary Design Folder(s) to the Structural Resource Manager. An acknowledgement email is sent to the district contact(s) informing them that the Bridge Division has received the Bridge Survey. The email subject line should include the Job No., County and Route. Include the Bridge No(s). and the name of the Bridge Division contact in the email.
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Once the survey is found to be complete and accurate, the Survey Complete date should be entered into Bloodhound. This date should match the Surv Rec date if no changes were made. If the survey is not complete or contains inaccuracies as submitted, we need to work with the district to fill in the blanks. If the omissions affect the timeline for completing the preliminary design, the Survey Complete date should reflect the date when we have all the information needed for the preliminary design to move forward without delay. If there is a delay in the bridge division review of the survey, this time should not count against the district in the survey complete date. The Bridge Survey Processor should work closely with the preliminary designer and SPM to determine the proper Survey Complete date in this case. For example, a bridge survey is received on 9/16/2016. Initial review by the bridge survey processor shows a complete survey. The job sits for five weeks while a preliminary resource comes available. Review by the preliminary designer shows a profile grade that is unusable and the preliminary design cannot progress until the grade situation is corrected. It takes four weeks for the grade to get worked out. The Survey Complete date should be four weeks after the Surv Rec date (10/14/2016). The district would not be penalized for our five week delay in reviewing the survey. This date is important because it will help us track when bridge surveys are turned in relative to when they are complete and when the project is due to Design.
  
 
===751.1.1.3 Beginning Preliminary Design===
 
===751.1.1.3 Beginning Preliminary Design===
  
Once the Preliminary Designer is assigned to a structure, they should meet with the Structural Project Manager to go over the Correspondence and Layout files to see if anything out of the ordinary has come up at Core Team Meetings prior to that date. It is important that any correspondence or calculations used in the laying out of the structure should be included in the bound portion of the Layout Folder.
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The Preliminary Designer should meet with the Structural Project Manager to go over the Correspondence and Preliminary Design files to see if anything out of the ordinary has come up at Core Team Meetings prior to that date. It is important to include any correspondence or calculations used in the laying out of the structure in the bound portion of the Preliminary Design Folder.  
  
The Preliminary Designer should then examine the Bridge Survey closely for any errors or omissions. Consult Section [[748.7 Bridge Reports and Layouts|Bridge Reports and Layouts]]. Pay special attention to the scales used. Make sure the district's submittal includes photographs and details of staging and/or bypasses (if applicable). Contact the district to resolve any discrepancies or questions.  Look at the Bridge Survey cover letter to determine who the District Contact is.
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The Preliminary Designer should then examine the Bridge Survey closely for any errors or omissions. Consult [[:Category:747 Bridge Reports and Layouts|EPG 747 Bridge Reports and Layouts]]. Pay special attention to the scales used. Make sure the district's submittal includes photographs and details of staging and/or bypasses, if applicable. Verify that the proposed roadway width meets the NBI criteria for minimum bridge roadway width to avoid building a deficient bridge. Contact the district to resolve any discrepancies or questions.
  
A visit to the bridge site by the Preliminary Designer may be warranted to help determine Manning’s “n” values, examine adjacent properties, etc.  If you decide to make this trip, advise the Structural Project Manager and the District Contact since they may also want to attend.
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A visit to the bridge site by the Preliminary Designer may be warranted to help determine Manning’s “n” values, examine adjacent properties, etc.  If you decide to make this trip, advise the Structural Project Manager and the district contact since they may also want to attend.
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'''Vertical Alignment and Bridge Deck Drainage'''
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Laying out a bridge should consider deck drainage concerns for bridges on flat grades and sagging vertical curves and other vertical alignment issues as given in [[230.2 Vertical Alignment|EPG 230.2 Vertical Alignment]] and [[230.2 Vertical Alignment#230.2.10 Bridge Considerations|EPG 230.2.10 Bridge Considerations]].
  
 
===751.1.1.4 Coordination, Permits, and Approvals===
 
===751.1.1.4 Coordination, Permits, and Approvals===
  
The interests of other agencies must be considered in the evaluation of a proposed stream-crossing system, and cooperation and coordination with these agencies must be undertaken. Coordination with the State Emergency Management Agency (SEMA), the U.S. Coast Guard, the U.S. Army Corps of Engineers, and the Department of Natural Resources is required.
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The interests of other agencies must be considered in the evaluation of a proposed stream-crossing system; cooperation and coordination with these agencies must be undertaken. Coordination with the State Emergency Management Agency (SEMA), the U.S. Coast Guard, the U.S. Army Corps of Engineers, and the Department of Natural Resources is required.
  
 
Required permits include:
 
Required permits include:
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Section 404 and Section 401 permits are obtained by the Design Division. U.S. Coast Guard permits are obtained by the Bridge Division. The Bridge Division will obtain floodplain development permits for projects that include structures in a regulated floodplain. The Design Division will obtain floodplain development permits for other projects involving roadway fill in a regulated floodplain.
 
Section 404 and Section 401 permits are obtained by the Design Division. U.S. Coast Guard permits are obtained by the Bridge Division. The Bridge Division will obtain floodplain development permits for projects that include structures in a regulated floodplain. The Design Division will obtain floodplain development permits for other projects involving roadway fill in a regulated floodplain.
  
Copies of approved U.S. Coast Guard permits and floodplain development permit/applications are sent to the District, with a copy to the Design Division.
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Copies of approved U.S. Coast Guard permits and floodplain development permit/applications are sent to the district, with a copy to the Design Division.
  
 
See [[:Category:127 MoDOT and the Environment|MoDOT and the Environment]] for more information on the required permits.
 
See [[:Category:127 MoDOT and the Environment|MoDOT and the Environment]] for more information on the required permits.
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===751.1.1.5 New Regular Bridge Design Schedule (Nonseismic) (Nonrailway Crossing)===
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[[image:751.1.1.5 Sept 28 2016.jpg|center|975px]]
  
 
==751.1.2 Bridges/Boxes==
 
==751.1.2 Bridges/Boxes==
 
===751.1.2.1 End Slopes/Spill Fills===
 
===751.1.2.1 End Slopes/Spill Fills===
  
 
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The end slopes are determined by the Construction and Materials Division and are supplied to the Bridge Division by way of the Preliminary Geotechnical Report.  If this report is not in the Correspondence file, contact the district to get a copy of it.  The Bridge Division has made a commitment to the districts that we will have the bridge plans, specials and estimate completed 12 months after the date the Bridge Survey and Preliminary Geotechnical Report are received.  The "12 month clock" does not start ticking until both the Bridge Survey and the Preliminary Geotechnical Report are in the Bridge Division.
The end slopes are determined by the Construction and Materials Division and are supplied to the Bridge Division by way of the Preliminary Geotechnical Report.  If this report is not in the Correspondence file, contact the District to get a copy of it.  The Bridge Division has made a commitment to the districts that we will have the bridge plans, specials and estimate completed 12 months after the date the Bridge Survey and Preliminary Geotechnical Report are received.  The "12 month clock" does not start ticking until both the Bridge Survey and the Preliminary Geotechnical Report are in the Bridge Division.
 
  
 
When laying out a skewed structure, adjust the end slope for the skew angle.  On higher skews, this will have a significant effect on the lengths of the spans.  Often the slope of the spill fills will be steeper than the roadway side slopes.  On a skewed structure, this makes it necessary to "warp" the slopes.
 
When laying out a skewed structure, adjust the end slope for the skew angle.  On higher skews, this will have a significant effect on the lengths of the spans.  Often the slope of the spill fills will be steeper than the roadway side slopes.  On a skewed structure, this makes it necessary to "warp" the slopes.
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===751.1.2.2 Wing Lengths===
 
===751.1.2.2 Wing Lengths===
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The purpose of wings is to contain and stabilize the abutment fill as the roadway transitions to the bridge. For stream crossings in particular, the wings also protect the abutment during extreme hydraulic events. 
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The lengths of the wings at the end bents are to be determined prior to the issuance of the Bridge Memorandum.  There are two reasons for this.  First, the district will use these lengths to determine the placement of their guardrail (bridge anchor section).  Second, if the lengths of the wings exceed 22 ft., they will have to be broken into a stub wing and a detached wing wall.  If this happens, then you will need to include this extra cost in your Preliminary Cost Estimate and request soundings for the wall.  The request for soundings for the wall should include a request for the determination of the allowable bearing of the soil (if in cut - assume piling if it is in fill) and the angle of internal friction for the material retained by the detached wing wall.  Also include the bottom of wing footing elevation.
  
The lengths of the wings at the end bents are to be determined prior to the issuance of the Bridge Memorandum. There are two reasons for thisFirst, the district will use these lengths to determine the placement of their guardrail (bridge anchor section). Second, if the lengths of the wings exceed 22 feet, they will have to be broken into a stub wing and a detached wing wallIf this happens, then you will need to include this extra cost in your Preliminary Cost Estimate and request soundings for the wall.  The request for soundings for the wall should include a request for the determination of the allowable bearing of the soil (if in cut - assume piling if it is in fill) and the angle of internal friction for the material retained by the detached wing wall. Also include the bottom of wing footing elevation.
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In order to use a standard end section for Type D barrier on a short turned-back wing, consider increasing the wing length so that the barrier end section is at least 8 feet long.
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'''Unequal Wing Lengths'''
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Wing lengths at each end of a bridge could be unequal because of several factors: grade of roadway under, superelevation of bridge, skew of the bridge, and/or other ramps/roads/slopes adjacent to the bridge structure, e.g., stream access roads or unusual geomorphic conditions.   
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Set/determine the wing lengths using the control points, as shown in [[Media:611.1 Embankment at Bridge Ends.pdf|Embankment at Bridge Ends]], which may be used for both grade separations and stream crossings. This is done after the end bent location is determined. If estimated wing lengths are within 3 ft., they should be made equal and based on the longer wing lengthMake sure no slope is steeper than that recommended in the geotechnical preliminary reportSlightly flatter slopes are acceptable. The contractor will warp the slopes to fit the wing tip locations.
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Equal wing lengths are preferable at stream crossings to mitigate scour, improve erosion control and improve/mitigate parallel water flow along wing and side embankment. Also, since wing lengths are reported to districts for use in estimating rock slope protection limits, unequal lengths (especially on the upstream side) could mistakenly lead to the unfavorable condition of allowing for less than adequate rock side slope protection.
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Judgement is required since no two estimated wing lengths at a bridge end will be exactly equal. More often equal wing lengths are used.
  
 
On divided highway bridges with high skews and shallow end slopes, the wing lengths on the median side of the bridge may be less than the other side due to the difference in sideslope between the median and the outside.
 
On divided highway bridges with high skews and shallow end slopes, the wing lengths on the median side of the bridge may be less than the other side due to the difference in sideslope between the median and the outside.
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Determining the most appropriate skew angle for the structure involves some judgement.  On bridges over streams, pick the angle that will allow floodwater to pass through the bridge opening with the least amount of interference from intermediate bent columns.  Another consideration on meandering streams is to avoid a skew which will cause the spill fill – side slope transition from blocking the stream.  Often a trip to the field may be justified just for determining the angle (you can even ask the district to stake some different skews for you to observe in the field).
 
Determining the most appropriate skew angle for the structure involves some judgement.  On bridges over streams, pick the angle that will allow floodwater to pass through the bridge opening with the least amount of interference from intermediate bent columns.  Another consideration on meandering streams is to avoid a skew which will cause the spill fill – side slope transition from blocking the stream.  Often a trip to the field may be justified just for determining the angle (you can even ask the district to stake some different skews for you to observe in the field).
  
On stream crossings, avoid skews between zero and five degrees and try to use five degree increments.  On grade separations, often the skew must be accurate to the nearest second to maintain minimum horizontal clearances.
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On stream crossings, avoid skews between zero and five degrees and try to use five-degree increments.  On grade separations, often the skew must be accurate to the nearest second to maintain minimum horizontal clearances.
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Keep all bents on a bridge parallel whenever possible and avoid skews over 55 degrees (30 degrees for adjacent prestressed concrete beams).  Also keep in mind that the higher the skew, the higher the Preliminary Cost Estimate due to the beam caps and wings being longer.
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===751.1.2.5 Bridge Width ===
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 +
For bridge width requirements, see [[231.8 Bridge Width|EPG 231.8 Bridge Width]].
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===751.1.2.6 Vertical and Horizontal Clearances===
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====751.1.2.6.1 Grade Separations====
  
Keep all bents on a bridge parallel whenever possible and avoid skews over 55 degrees. Also keep in mind that the higher the skew, the higher the Preliminary Cost Estimate due to the beam caps and wings being longer.
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{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
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|-
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!style="background:#BEBEBE" colspan="3"|Minimum Design Clearances for New Bridges
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|-
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!style="background:#BEBEBE"|Facility Under Bridge!!style="background:#BEBEBE"|Vertical Clearance under Superstructure<sup>1</sup>!!style="background:#BEBEBE"|Horizontal Clearance
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|-
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|Interstate and Principal Arterial Routes|| 16’-6” over roadway including auxiliary lanes and shoulders||rowspan="4" width="475"|Clear zone clearances from the edge of the traveled way (includes shoulders and auxiliary lanes) are obtained from the District Design Division. The vertical clearance is required for the full width of the clear zone. Barrier is required if unable to locate obstacles outside clear zone (columns, beams, walls, coping, 3:1 [1V:3H] slopes or steeper). If a barrier is required the minimum distance to the barrier shall be specified on the Bridge Memorandum as the horizontal clearance otherwise the clear zone clearance shall be used. See [[751.2 Loads#751.2.2.6 Other Loads|EPG 751.2.2.6 Other Loads]] and [https://www.modot.org/media/16857 Standard Plans 606.01], [https://www.modot.org/media/16865 606.51] and [https://www.modot.org/media/16893 617.10] for typical barrier and railing options.
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|-
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|Other State Routes with Volumes ≥ 1700 vpd ||16’-6” over roadway including auxiliary lanes and shoulders
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|-
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|Other State Routes with Volumes < 1700 vpd ||15’-6” over the roadway including auxiliary lanes and shoulders<sup>'''2'''</sup>
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|-
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|Other Streets and Roads ||14’-6” (15’-6” commercial zones) over the roadway including auxiliary lanes and shoulders<sup>'''2'''</sup>
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|-
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|Railroads ||23’-0” inside 18’-0” opening or as required by railroad (23’-4” for UPRR, 23’-6” for BNSF)<sup>'''3'''</sup>||14’-0” and 22’-0” from centerline<sup>'''4,5'''</sup><br/>(25’-0” eliminates collision walls)
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|-
 +
|colspan="3"|<sup>'''1'''</sup> Roadway vertical clearances are based upon AASHTO minimums with an additional 6 inches to accommodate future resurfacing of the roadway. An additional 1 ft. is required for pedestrian overpass facilities over roadways. Vertical clearances shown are also applicable when the facility under the bridge is being carried by a bridge.<br/><sup>'''2'''</sup> To provide continuity of travel for taller vehicles exceptions can be made both rural and urban for any routes connecting to the systems where taller vehicles are allowed but not to exceed 16.5 feet.<br/><sup>'''3'''</sup>  Clearance is measured from the top of rails (from top of high rail on superelevated track). The required 18-ft. opening centered on the track shall be increased on each side of centerline 1.5 inches per each degree of curvature for any track crossed.<br/><sup>'''4'''</sup> Fourteen feet is a preferred minimum. The absolute minimum is 9 ft. from the centerline plus 1.5 inches per each degree of any track curvature.<br/><sup>'''5'''</sup>  The minimum clearance of 22 ft. to be provided on one side of the track(s) is for off-track maintenance. If it is not obvious on which side of the track(s) this clearance is provided, a decision should be obtained from railroad's local representative. Assistance from Multimodal Operations may be required in some situations.
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|}
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{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
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|-
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!style="background:#BEBEBE"|Clearance over Traffic During Construction (New and Existing Structures)
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|-
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|'''Roadways:''' Consult with the structural project manager or the structural liaison engineer and the district contact for minimum allowable vertical and horizontal clearance. Vertically this is usually 12 to 18 inches below the final minimum vertical clearance. Horizontally this is usually a minimum number of lanes or minimum size of opening required during the project while specifying the locality of the opening (e.g. centered on existing lanes, two 12-ft. lanes minimum in each direction, etc.).<br/>These clearances shall be specified on the Bridge Memorandum to be used in the note required on the final plans. For note see [[751.50 Standard Detailing Notes#A3. All Structures|EPG 751.50 A3. All Structures]].
 +
|-
 +
|'''Railroads:''' If feasible, 15 ft. horizontally from centerline of track and 21.5 ft. vertically from tops of tracks (from top of high rail on superelevated track). If either of these clearances is not feasible then obtain acceptable clearances from the railroad projects manager. For the detail required on the final plans showing minimum clearances during construction over railroads, see [[751.5 Structural Detailing Guidelines#751.5.2.1.2.7 Features Crossed|EPG 751.5.2.1.2.7 Features Crossed]].
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|}
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 +
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
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|-
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!style="background:#BEBEBE"|Deficient Vertical Clearances on Interstates
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|-
 +
|Refer to [[131.1 Design Exception Process#131.1.7 Deficient Vertical Clearances on Interstates|EPG 131.1.7 Deficient Vertical Clearances on Interstates]] for information about coordinating minimum vertical clearance for grade separation structures with the Defense Department.
 +
|}
  
===751.1.2.5 Structure Type Selection===
+
====751.1.2.6.2 Stream Crossings====
 +
For vertical clearance on stream crossings, see [[748.3 Freeboard|EPG 748.3 Freeboard]].
  
As the size of the creek/river increases, here is a rough approximation of structure type selection:
+
===751.1.2.7 Structure Type Selection===
  
 +
Both steel and prestressed concrete girders shall be considered on all structure type selections. As the required span length of the structure increases to bridge the obstruction, deeper girder sections will be required.  As a general rule of thumb, span to superstructure depth ratios (S/D) will be on the order of 20 to 30 with the higher numbers being slender, flexible structures. 
  
:Box Culvert (single, double or triple)
+
Preliminary designers should consider these structure types as the span length increases with the top of the list providing the least amount of span capability.  Economic consideration should be given to the selection of steel or concrete superstructures.  Recent and relevant bid history for each structure type should be reviewed during the preliminary design phase. 
:Prestressed I-Girder (type 2, 3, 4 or 6)
+
:* Concrete Box Culvert (single, double or triple cell)
:Prestressed Bulb-Tee Girder (63.5” or 72.5")
+
:* Prestressed or Reinforced Concrete Slab
:Plate Girder
+
:* Adjacent Prestressed Concrete Box or Voided Slab Beams (with approval of Structural Project Manager)
 +
:* Shallow Depth Girder Sections: Wide Flange Steel Beams, Spread Prestressed Concrete Beams (Box or Voided Slab), Prestressed I-Girders (Type 2, 3, 4 or 6), or Prestressed NU-Girders (PSNU-35 or PSNU-43)
 +
:* Intermediate Depth Girder Sections: Plate Girder, Prestressed Bulb-Tee Girder (63.5” or 72.5") or Prestressed NU Girder (PSNU-53, 63, 70 or 78)
 +
:* Deep Girder Sections: Plate Girder (greater than 78” web depth)
  
 +
Voided slab beams are currently only produced by one manufacturer and therefore a long transport may need to be considered in the bridge memo estimate.
  
Sometimes a Solid Slab, Voided Slab, Prestressed Box Girders, Prestressed Voided Slab Beams or NU Girder bridge will need to be used instead of a Prestressed I-Girder due to limited vertical clearance or freeboard.  Other times a Plate Girder or Wide Flange may need to be used instead of a Prestressed I-Girder for the same reasonHigher strength concrete girders may allow you to span further with shallower girders.
+
Often site conditions warrant the use of shallower depth girder sections to maximize vertical clearance over roads or railroads or to maximize freeboard over streamsWhen contemplating these situations, the preliminary designer should work with the district highway designer to provide several structure depth options with corresponding roadway profile grade raises.  It may be that a more expensive bridge structure results in an overall minimized project costHigh strength concrete or high-performance steel grades may allow the preliminary designer to span longer distances with shallower structures.  These higher strength materials may also be used to eliminate girder lines as roadway width increases.
  
Higher strength concrete prestressed I-girders should also be considered as a means to save money by eliminating girder lines.
+
On multi-span structures, it is generally more efficient to have a balanced span arrangement where the end spans are approximately 10 percent shorter than the intermediate spans.  This type of arrangement balances the positive moment demand at the midspans with the negative moment demand at the intermediate bents and allows optimization of the structural cross section.  For example, a span layout of (67’ - 76’ - 67’) is structurally more efficient than (70’-70’-70’).
  
Prestressed concrete double-tee girders should be avoided if possible due to the redecking concerns for future maintenance.
+
===751.1.2.8 Box Culverts===
  
On grade separations with high skews, you may want to consider using a 4 span bridge with integral end bents rather than a 2 span bridge with semi-deep abutments. This should be considered if the semi-deep slab length exceeds 30’.
+
Most districts prefer a box culvert to a bridge because of the lower maintenance costs; however, if a stream crossing is on the borderline between a box culvert and a bridge, each option should be explored and presented to the district. The presentation to the district should include the cost estimate for each option as well as a recommendation as to which option is preferred by the Bridge Division. Keep in mind that box culverts should be avoided on streams with medium to heavy drift. If the stream being crossed is a drainage ditch it is advisable to have the district contact the drainage district to see if they have any specific objections (i.e. drift etc.) to using a culvert at the proposed location. Approval of proposed structure layout by the drainage district may be required, see [[:Category:747 Bridge Reports and Layouts#747.3.4 Bridge Permits or Approvals by Other Agencies|EPG 747.3.4 Bridge Permits or Approvals by Other Agencies]].
  
On Prestressed I-Girder bridges, it is usually more cost effective to shorten the end spans of a 3 span Prestressed I-Girder bridge rather than having all spans the same length. The optimum span ratio is 1.1 to 1.0. For example, a span layout of (67’ - 76’ - 67’) is structurally more efficient than (70’-70’-70’).
+
====751.1.2.8.1 Hydraulic Design====
 +
A general rule of thumb for the use of a culvert is that it can handle about 1,000 cfs per cell with 3 cells being the usual maximum. This can vary if the slope of the streambed is unusually flat or steep. Another rule of thumb is that the water from a drainage area of less than 5 square miles can usually be handled by a concrete box culvert.  Curves or bends should be avoided when possible. See [[750.2 Culverts#750.2.3.2.2 Head Loss Due to Bends|EPG 750.2.3.2.2 Head Loss Due to Bends]] when curves or bends will be used.
  
===751.1.2.6 Box Culverts===
+
For details of hydraulic design, see [[750.2 Culverts|EPG 750.2 Culverts]].
{|style="padding: 0.3em; margin-left:15px; border:1px solid #a9a9a9; text-align:center; font-size: 95%; background:#ffddcc" width="210px" align="right"
 
|-
 
|'''Concrete Box Culvert, GFRP'''
 
|-
 
|[http://library.modot.mo.gov/RDT/reports/RI99028/RDT01016a.pdf Report 2001]
 
|-
 
|'''See also:''' [http://www.modot.gov/services/OR/byDate.htm Innovation Library]
 
|}
 
A general rule of thumb for whether or not a culvert may be used in place of a bridge is...
 
The most a culvert can handle is about 1,000 cfs per cell with 3 cells being the usual maximum.  This can vary if the slope of the streambed is unusually flat or steep.  Another rule of thumb is that the water from a drainage area of less than 5 square miles can usually be handled by a concrete box culvert.
 
  
Most districts prefer a box culvert to a bridge because of the lower maintenance costs; however, if a stream crossing is on the borderline between a box culvert and a bridge, each option should be explored and presented to the district. The presentation to the district should include the cost estimate for each option as well as a recommendation as to which option is preferred by the Bridge Division.  Keep in mind that box culverts should be avoided on streams with medium to heavy drift, as shown on the Bridge Survey.
+
Hydraulic designs and plans for some small box culverts are handled by the district. See [[750.7 Non-Hydraulic Considerations#750.7.4.3 Summary of Responsibilities|EPG 750.7.4.3 Summary of Responsibilities]] for responsibility for analysis, design and final plans preparation.
  
Hydraulics for some small box culverts are handled by the district. For drainage areas of 1,000 acres (approx. 1.5 sq. miles or 2.5 sq. kilometers) or less, the district will do the hydraulics.  For drainage areas larger than this, the Bridge Division will do the hydraulics.
+
====751.1.2.8.2 Environmental Requirements====
  
If you must curve or kink your concrete box culvert, try to limit each bend to 15 degrees. The FHWA publication HDS-5 “Hydraulic Design of Highway Culverts” recommends that you space these bends a minimum of 50 feet apart.  If this is not practical, you will need to account for the head loss resulting from the sharper bend.
+
See [[750.7 Non-Hydraulic Considerations#750.7.3 Environmental Requirements|EPG 750.7.3 Environmental Requirements]] for details of embedment, velocity and conveyance requirements.
  
The Final Design of box culverts (structural calculations and contract plans preparation) will be done by the Bridge Division unless it is a single cell box culvert, in which case the plans are done by the district.
+
====751.1.2.8.3 Layout====
  
When sizing the proposed concrete box culvert, use the standard cell sizes whenever possible. Consult the most recent set of Missouri Standard Plans to determine the current standard cell sizes.
+
=====751.1.2.8.3.1 Size=====
 +
When sizing the proposed concrete box culvert, use Standard Box Culvert Sizes whenever possible. For information on standard box culverts sizes, see [[750.7 Non-Hydraulic Considerations#750.7.4.1 Standard Plans|EPG 750.7.4.1 Standard Plans]]. For additional information on culvert size, see [[750.7 Non-Hydraulic Considerations#750.7.4.4 Size|EPG 750.7.4.4 Size]].
 +
 +
=====751.1.2.8.3.2 Length=====
  
Locate the inside face of the headwalls of the culvert at or beyond the edge of the roadway clear zone. It is best to confirm this with the district because they may have gotten a [[131.4 Design Exception Process|design exception]]. If the headwalls cannot be placed beyond the clear zone, common in the situation of a very low fill, then guardrail will need to be attached to the top slab at least 10” from the headwall of the culvert.  
+
The inside face of the headwall is located at the intersection of the roadway fill slope and the top of the top slab of culvert. Typically, the longest barrel is produced considering this intersection point upgrade. Flared inlets, varying roadway widths, clear zones and guardrail placement are possible exceptions to this rule.  
  
Check the Preliminary Geotechnical Report for recommendations concerning the use of collars on longer box culvertsThese are called for in the Preliminary Geotechnical Report when substantial differential settlement is expected.
+
When [[231.2 Clear Zones|clear zones]] are provided, locate the inside face of the headwalls of the culvert at or beyond the edge of the roadway clear zone. In situations of very low fill, contact the district to determine if the use of guardrail is preferred to placing the headwalls beyond the edge of the clear zone.  When clear zones are not provided the district will determine the need for guardrail on a case by case basis. Typically when guardrail is to be used over a culvert the typical section will show a 3’-5” shoulder widening as shown in [https://www.modot.org/media/16856 Standard Plan 606.00]. Consult the district if it is unclear whether adequate clear zones are provided or if guardrail is to be used over a box culvertIf the fill over the culvert is shallow, [[750.7 Non-Hydraulic Considerations#750.7.4.5 Guardrail Attachment|guardrail attachment]] may need to be provided. It may be advisable to lengthen culverts with shallow fill slightly to provide room for future guardrail attachments if guardrail over the box culvert is not provided.
  
Do not allow the precast option on box culvert extensions or other "oddball" situations.
+
=====751.1.2.8.3.3 Roadway Fill=====
 +
Minimum roadway fill height is determined at the outside shoulder line and is the greater of 1 ft. or the thickness of the pavement and base material specified in [[750.7 Non-Hydraulic Considerations#750.7.11.1 Minimum Fill Heights|EPG 750.7.11.1 Minimum Fill Heights]]. Pavement and shoulder widths and thicknesses are determined on a project by project basis. Pavement and shoulder details (i.e., width, thickness, alternate pavement options) can be obtained from the district if needed, but based on maximum pavement thicknesses and minimum shoulder widths, fill heights at the outside of the shoulder of 20 ½” or greater on major routes or 14 ½” or greater on minor routes will not require pavement or shoulder details. For more information on pavement and shoulder widths and thicknesses see [[Other Aspects of Pavement Design|Other Aspects of Pavement Design]] and [[:Category:231 Typical Section Elements for Roadways|EPG 231 Typical Section Elements of Roadways]].  
  
===751.1.2.7 Girder Type Selection===
+
Roadway fill outside of the shoulders shall be warped (in the past this was referred to as the fill being “rolled up and over”) to provide a minimum of 12 in. of cover where the top of the culvert could be exposed. A standard note should be shown on the [https://epg.modot.org/index.php?title=751.1_Preliminary_Design#751.1.2.17_Bridge_Memorandums Bridge Memorandums] (Memos) regarding warping the roadway fill. [[media:751.1.2.8.3.3.pdf|Cases where this could occur]] are:
  
Once you have determined that your structure will have girders, you must decide what types of girders to use.  For checking your vertical clearance or freeboard, you will need to know the maximum span length of each type of girder. See [[751.22_P/S_Concrete_I_Girders#751.22.1.3_Typical_Span_Ranges|751.22 P/S Concrete I Girders]] or [[751.14_Steel_Superstructure#751.14.1.2_Girder_Limits_and_Preferences|751.14 Steel Superstructure]].  You will need to make adjustments if the span ratios get over 1.25.
+
:1. Culvert ends with shallow fill and headwalls located outside of the clear zone.  
 +
:2. Median of a divided highway with shallow fill.  
 +
:3. Flared Inlets
 +
:4. Auxiliary lane or outer road with skews different than that of the mainline
 +
:5. Steep grade with a wide or skewed culvert.
  
Notify the District Contact as soon as you know that the profile grade will need to be raised to meet the minimum vertical clearance or freeboard requirements. If the district says the profile grade can’t be raised, consider using more girder lines, using higher strength concrete if Prestressed I-Girders or NU Girders are being used, or switching to a voided slab bridge. As a last resort, request a [[131.4 Design Exception Process|design exception]] for the substandard item.
+
For additional information of roadway fill, see [[750.7 Non-Hydraulic Considerations#750.7.11 Overfill Heights|EPG 750.7.11 Overfill Heights]].
  
Prestressed I-Girder types 2, 3 and 4 cost roughly the same per foot ($100) and even the type 6 girders cost only slightly more ($130/ft.).
+
=====751.1.2.8.3.4 Fill Settlement=====
 +
Check the Preliminary Geotechnical Report for recommendations concerning [[750.7 Non-Hydraulic Considerations#750.7.8 Fill Settlements|fill settlements]] and the use of [[751.8 LRFD Concrete Box Culverts#Collar Beams|collar beams]] on longer box culverts. Cambering of the culvert should also be considered when fill settlements are appreciable. For more information, see [[750.7 Non-Hydraulic Considerations#750.7.9 Camber in Culverts|EPG 750.7.9 Camber in Culverts]].
  
If you decide to go with a Prestressed Bulb-Tee Girder, try to limit the maximum span to 125'. We have gone as far as 133' but the strands had to be at 1 1/2" centers. Also keep in mind that these types of girders are very heavy and will often require two or three cranes to set them and may be difficult to transport to the site.
+
====751.1.2.8.4 Precast Box Culvert Sections====
 +
If the use of precast box culvert sections will not be allowed to be substituted for cast-in-place construction or if precasting is required it should be noted on the bridge memorandum and on the bridge plans.  
  
If you decide to use Plate Girders, then you have to decide if the girders should be painted or not.  The use of weathering steel (ASTM A709 Grades 50W and HPS70W) is preferred due to the lower maintenance costs; however, there are situations where the use of weathering steel is not advisable.  Here is a brief list of times when weathering steel should NOT be used (based on FHWA Technical Advisory T5140.22):
+
Precast option for box culvert extensions will be permitted using a cast-in-place connection where the centerline of new cells is not laterally displaced more than 15° (maximum) from the centerline of existing cells for each cell extension.  
  
#If the distance from Ordinary High Water to low steel is less than 8' (or 3’ between Des. High Water and low steel).
+
====751.1.2.8.5 Abrasion====
#If the bridge is located in either the St. Louis or Kansas City urban areas.
+
If a culvert requires design for abrasion it should be noted on the bridge memorandum. For more information see [[750.7 Non-Hydraulic Considerations#750.7.4.2 Abrasion of Interior Surfaces|EPG 750.7.4.2 Abrasion of Interior Surfaces]].
#If the bridge is over a road with an ADT greater than 10,000.  
 
#If the bridge is over a road with an ADTT greater than 1,200.
 
  
If the vertical clearance is at least 25’, the limitations of 2.), 3.) and 4.) do not apply.
+
===751.1.2.9 Girder Type Selection===
  
If weathering steel cannot be used, the girders should be painted gray (Federal Standard #26373)If the district doesn’t want gray, they can choose brown (Federal Standard #30045). If the district or the local municipality wants a color other than gray or brown, they must meet the requirements of [[1045.5_Policy_on_Color_of_Structural_Steel_Paint|Section 1045.5 Policy on Color of Structural Steel Paint]].  System H paint should be used on weathering steel while System G should be used on all other steel plate girders.
+
Once it has been determined that the structure will have girders, the types of girders to be used must be identifiedTo check the vertical clearance or freeboard, the maximum span length of each type of girder must be known.  See [[751.22_P/S_Concrete_I_Girders#751.22.1.3_Typical_Span_Ranges|EPG 751.22 P/S Concrete I Girders]] or [[751.14_Steel_Superstructure#751.14.1.2_Girder_Limits_and_Preferences|EPG 751.14 Steel Superstructure]].  Adjustments will need to be made if the span ratios become greater than 1.25.
  
===751.1.2.8 Longer Bridges===
+
If it is determined that the roadway profile grade will need to be raised (or lowered) to provide additional vertical clearance or freeboard, the preliminary designer should notify the district contact as soon as possible.  It is best to provide the district with several options of varying profile grade elevation increase with varying structural depth.  Larger grade elevation increases typically result in longer bridges as spill slopes dictate bridge length.  The preliminary designer and district contact should work together to minimize the overall project cost even if the bridge cost is slightly more expensive.  Consider the various structure types listed in [[#751.1.2.7 Structural Type Selection|EPG 751.1.2.7 Structural Type Selection]] when selecting the girder type.  Also consider that adding girder lines or using higher strength material (concrete or steel) may allow longer or shallower spans for a given girder cross section.  As a last resort, request a [https://epg.modot.org/index.php/131.1_Design_Exception_Process design exception] for the substandard item.
  
For bridges that are longer than normal (more than 6 spans being a general rule of thumb), other items must be considered. If the feature you are crossing allows flexibility in bent placement, the most cost efficient span length is one that will result in the cost of one span's superstructure being equal to the cost of one bent.  For example, calculate the cost of one intermediate bent, and then adjust the length of the span until the cost of the girders, slab and curb equal the cost of the bent.  The use of higher strength concrete in Prestressed I-Girders can allow spans to be increased 16% to 21% as a means to eliminate intermediate bents.
+
====751.1.2.9.1 Concrete Girder Options====
 +
Prestressed girder selection should use the following order for trial sizing and spanning:
 +
:Prestressed or reinforced concrete slab beams
 +
:Prestressed Concrete Box Beams
 +
:MoDOT Standard Prestressed Girders Type 2, 3, 4 and 6
 +
:NU Standard Prestressed Girders Type 35, 43, 53, 63, 70 and 78
 +
:MoDOT Bulb-Tees Type 7 and 8
  
Another item to consider is the placement of expansion devicesBe sure to include the costs of the expansion devices and deadman anchors (if applicable) in your Preliminary Cost Estimate.
+
For span lengths longer than 125 feet for prestressed concrete, the girders become very heavy and are difficult to transport to the site and often require two or more large cranes to place on the supportsThe preliminary designer should discuss this with the district, and have it documented on the Constructability Questionnaire noted in [[#751.1.2.18.3 Supporting Documents|EPG 751.1.2.18.3 Supporting Documents]].
  
===751.1.2.9 Staged Construction===
+
====751.1.2.9.2 Steel Girder Options====
 +
When considering steel structures, the preliminary designer must decide if the girders should be painted or fabricated from weathering steel.  If site-specific conditions allow, the use of unpainted weathering steel (ASTM A709 Grades 50W and HPS70W) should be considered and is MoDOT’s preferred system for routine steel I-girder type bridges due to its performance, economic and environmental benefits.  Cost savings are realized because of the elimination of the initial paint system as well as the need for periodic renewal of the paint system over the life of the structure.
  
If the new structure you are laying out replaces an existing structure, the exact details of the staging must be coordinated with the District ContactIf the new structure is on a new alignment, there is little cause for concern.  However, if the new structure is on the same or slightly different alignment, the location of the bents for the new structure should be spaced to avoid the existing substructure units if at all possible.
+
Weathering steels provide significant environmental and worker safety benefits as well.  Since they do not require initial and periodic repainting of the whole bridge, emissions of volatile organic compounds (VOC) are reduced.  Also, they generally do not require coating removal or disposal of contaminated blast debris over the service life of the structureBy eliminating the need for periodic repainting, the closing of traffic lanes can be prevented as well as the associated hazards to painters, maintenance workers, and the travelling public.
  
Also, if the new structure is on the same or slightly different alignment, the question of traffic handling will need to be addressedIf the district wants to use a temporary bypass, then you need to determine if the district can size some drainage-diversion pipes for the bypassIf the district decides pipes cannot be used, then a temporary bridge is necessaryA separate Bridge Survey/Memo/Bridge No. is required.
+
Partial coating of weathering steel is required near expansion jointsSee [[751.14 Steel Superstructure#751.14.5.8 Protective Coating Requirements|EPG 751.14.5.8]]Periodic recoating or overcoating will be required, however, on a much smaller scale than the whole bridge with the effect that lane closures and associated hazards are greatly reduced compared to painted steel.   
  
If the district does not want to use a temporary bypass, and they want to maintain traffic on the existing bridge while the new one is constructed, then the new structure will have to be stagedOne important item to verify in this situation is that the new girders will clear the existing substructureAnother item to consider in setting up the staging is the temporary barrier curb and required minimum horizontal distance from the edge of the deck based on whether the temporary barrier curb is attached to the slab.
+
Although weathering steel is MoDOT’s preferred system for routine I-girder bridges with proper detailing, it should not be used for box girders, trusses or other structure types where details may tend to trap moisture or debrisThere are also some situations where the use of weathering steel may not be advisable due to unique environmental circumstances of the siteGenerally, these types of structures would receive high deposits of salt along with humidity, or long-term wet conditions and individually each circumstance could be considered critical.
  
===751.1.2.10 Temporary Barriers===
+
The FHWA Technical Advisory T5140.22 October 1989 should be used as guidance when determining the acceptability of weathering steel. Due to the large amounts of deicing salts used on our highways which ultimately causes salt spray on bridge girders, the flowchart below should be used as guidance for grade separations. The flowchart, Fig. 751.1.2.9, below, is general guidance but is not all inclusive. There may be cases based on the circumstances of the bridge site where the use of weathering steel is acceptable even though the flowchart may indicate otherwise. In these cases, follow MoDOT’s [[131.1 Design Exception Process|design exception process]].
 +
 
 +
[[image:751.1.2.7 weathering steel Nov 2010.jpg|center|650px|thumb|<center>'''Fig. 751.1.2.9 Guidance on the Use of Weathering Steel for Grade Separations'''</center>
 +
'''*''' For multi-lane divided or undivided highways, consider the AADT and AADTT in one direction only.]]
 +
<div id="Weathering steel may be used"></div>
 +
Weathering steel may be used for stream crossings where 1) the base flood elevation is lower than the bottom of girder elevation and 2) the difference between the normal water surface and bottom of girder elevations is greater than 10 ft. for stagnant and 8 ft. for moving bodies of water.  Where the difference in elevations is less than noted, weathering steel may be used upon approval of the Assistant State Bridge Engineer.
  
Bridge Plans must include reference to Temporary Barrier attachment if required.  Coordination required with Design.
+
Additional documents that can be referenced to aid in identifying the site-specific locations and details that should be avoided when the use of weathering steel is being considered include:
  
:{|border="0"
+
:1. Transporation Research Board.  (1989).  ''Guidelines for the use of Weathering Steel in Bridges'', (NCHRP Report 314). Washington, DC: Albrecht, et al.
  
|valign="top"|a.||No attachment (Sufficient distance available to accommodate lateral deflection of barriers)
+
:2. American Iron and Steel Institute.  (1995). ''Performance of Weathering Steel in Highway Bridges, Third Phase Report''. Nickerson, R.L.
|-
 
|valign="top"|b.||Tie down strap system. (Refer to Standard Plan 617.20B)<br/>Coordinate with Design to provide minimum of 4 temporary barrier sections on approach slab roadway.
 
|-
 
|valign="top"|c.||Bolt through deck system (To be used only on existing decks, with sufficient strength, that will be removed.) (Refer to Standard Plan 617.20B) Coordinate with Design for required transition barrier attachments
 
|}
 
  
Lateral deflection requirements due to traffic impact on barriers must be considered if a project requires the use of Temporary BarriersWhen the Temporary Barrier is used in a free standing mode immediately adjacent to the edge of a bridge deck, the distance from the edge of the bridge slab to the center of gravity of the barrier shall be 45.3 inches minimum45.3 inches minimum shall be used where vertical displacement of traffic at edge of pavement is a safety issue.
+
:3. American Institute of Steel Construction(1993). ''Highway Structures Design Handbook'' (Vol. I, Chapter 9. Uncoated Weathering Steel Bridges). Pittsburgh, PA: Mathay, W.
  
 +
:4.  MoDOT. (1996). ''Missouri Highway and Transportation Department Task Force Report on Weathering Steel for Bridges''. Jefferson City, MO: Porter, P., et al.
 
   
 
   
<center>[[Image:751.1_Prelim_Design_Free_Standing_Temp_Barrier.gif]]</center>
+
The final brown rust appearance could be an aesthetic concern.  When determining the use of weathering steel, aesthetics and other concerns should be discussed by the Core Team members, with input from [https://modotgov.sharepoint.com/sites/br Bridge Division] and [https://modotgov.sharepoint.com/sites/mt Maintenance Division].
 +
 
 +
If weathering steel cannot be used, the girders should be painted gray (Federal Standard #26373).  If the district doesn’t want gray, they can choose brown (Federal Standard #30045).  If the district or the local municipality wants a color other than gray or brown, they must meet the requirements of [[1045.5_Policy_on_Color_of_Structural_Steel_Paint|EPG 1045.5 Policy on Color of Structural Steel Paint]].  System H paint should be used on weathering steel while System G should be used on all other steel plate girders.
 +
 
 +
===751.1.2.10 Longer Bridges===
 +
 
 +
For bridges that are longer than normal (more than 6 spans being a general rule of thumb), other items must be considered.  If the feature you are crossing allows flexibility in bent placement, the most cost-efficient span length is one that will result in the cost of one span's superstructure being equal to the cost of one bent.  For example, calculate the cost of one intermediate bent, and then adjust the length of the span until the cost of the girders, slab and curb equal the cost of the bent.  The use of higher strength concrete in Prestressed I-Girders or high performance steel in plate girders can allow spans to be increased approximately 20% as a means to eliminate intermediate bents.
 +
 
 +
Another item to consider is the placement of expansion devices.  Be sure to include the costs of the expansion devices and deadman anchors (if applicable) in your Preliminary Cost Estimate.
 +
 
 +
===751.1.2.11 Staged Construction===
 +
 
 +
If the new structure being laid out replaces an existing structure on the same alignment, the default method of handling traffic during construction is to close the road and detour traffic. The new substructure should be spaced to avoid the existing substructure units if at all possible.
 +
 
 +
If the district determines the road cannot be closed, the options for handling traffic include staged construction or using a temporary bypass.  If a temporary bypass is used, determine whether the district can size some drainage-diversion pipes for the bypass. If the district decides pipes cannot be used, then a temporary bridge is necessary and a separate Bridge Survey/Memo/Bridge No. is required.
  
 +
If the district decides to use staged construction, one important item to verify in this situation is that the new girders will clear the existing substructure. Another item to consider in setting up the staging is the placement and attachment requirements of the temporary concrete traffic barrier relative to the bridge deck and meeting horizontal distance requirements from the edge of the deck, which determines whether the temporary concrete traffic barrier is attached to the deck and how it is attached.
  
For all other applications of a free standing Temporary Barrier, the design lateral deflection of the barrier shall be 24 inches minimum.
+
===751.1.2.12 Temporary Barriers===
  
Regardless of deflection distance available, if the bridge deck is super elevated or has a large roadway slope, a free standing Temporary Barrier should not be used because the barrier has the potential for movement due to gravity forces on the barrier.
+
Bridge Plans must note whether temporary concrete traffic barrier is attached or freestanding, and if attached, whether they are attached with tie-down straps or bolt through deck attachment. Coordination is required with district Design. See [[617.1 Temporary Traffic Barriers|EPG 617.1 Temporary Traffic Barriers]] for more guidance.
  
When the Temporary Barrier is adequately attached to the bridge deck (Refer to Standard Plan 617.20B) minimum distance of 6 inches shall exist from the edge of the bridge slab to the face of the barrier.
+
:a. Where sufficient distance is available to accommodate lateral deflection of barriers: No attachment is required.  Note on plans as “Freestanding” or “No attachment required”.  
  
 +
:b. Where sufficient distance is not available to accommodate lateral deflection of barriers: Tie-down strap system is required. (Refer to [https://www.modot.org/media/16894 Standard Plan 617.20].) Coordinate with district Design to provide a minimum of four connected temporary concrete traffic barrier sections on approach slab roadway.
  
<center>[[Image:751.1_Prelim_Design_Attached_Temp_Barrier.gif]]</center>
+
:c. Where lateral deflection cannot be tolerated: Bolt through deck system is required.  (To be used only on existing decks that will be removed and that have sufficient strength.) (Refer to [https://www.modot.org/media/16894 Standard Plan 617.20].) Coordinate with district Design division for required transition barrier attachments that may be used on any deck, existing or new, where lateral deflection is not permitted with approval of the Structural Project Manager or Structural Liaison Engineer. 
  
===751.1.2.11 Earthquake Consideration===
+
[[Image:751.1.2.12 Freestanding.jpg|center|640px]]
+
<center>'''Freestanding Temporary Barrier'''</center>
If the structure you are laying out falls in seismic design category B, C or D, there are a few items to keep in mind.  Box culverts are preferable to bridges on stream crossings because they are exempt from seismic design unless crossing a known exposed fault.  Pile cap intermediate bents are preferable to open column bents on footings because footings can grow quite large due to seismic forces.  Minimize the number of expansion joints in the deck because each of these locations may require earthquake restrainers which are very costly.  Make the superstructure as light as possible, which usually means use steel plate girders or wide flanges instead of prestressed concrete girders where ever possible.  For shorter spans, voided and solid slab bridges perform well.
 
  
===751.1.2.12 Replacing an Existing Structure===
 
  
If you are replacing an existing structure with a new one, you may have to calculate a cost estimate for rehabilitating the old bridge. The sufficiency rating, which can be found on the SI&A form (Structure, Inventory & Appraisal), provides information on eligibility status of the bridge for using federal bridge (HBRRP) funds:
+
For all other applications of a freestanding temporary concrete traffic barrier, the preferred installation method requires a 2 ft. buffer area behind the barrier to allow for lateral deflection in both work areas and lane separation situations.
  
 +
Regardless of deflection distance (buffer area) available, if the bridge deck is super elevated or has a large roadway slope, a freestanding temporary concrete traffic barrier should not be used because the barrier has the potential for movement (“walking”) due to gravity forces and vibrations acting on the barrier.
  
{|border="1" cellpadding="5" cellspacing="0" align="center"
+
When a temporary concrete traffic barrier is adequately attached to a bridge deck (refer to Standard Plan 617.20) a minimum distance of 6 in. shall be provided from the edge of the bridge deck to the face of the barrier.
  
|''Status''||width="150"|''Sufficiency Rating (SR)''||''Comment''
 
|-
 
|Deficient||and SR < 50||Qualifies for full federal bridge replacement funds.
 
|-
 
|Deficient||and 50 < SR < 80||Qualifies for partial federal bridge replacement funds.
 
|-
 
|width="100"|Not Deficient||&nbsp;||Federal bridge replacement funds can not be used; however, other federal funds could possibly be used.
 
|}
 
  
 +
[[Image:751.1 Prelim Design Attached Temp Barrier.jpg|center|640px]]
 +
<center>'''Attached Temporary Barrier'''</center>
  
If the sufficiency rating is greater than 50 but less than 80, then a cost analysis will need to be included in the layout folder showing that it is a better value or more cost effective to replace the bridge than it is to rehab/widen it. If rehab/widen is more cost effective, a state may elect to replace the bridge; however, federal bridge replacement funds may be capped at 80% of the rehab/widen cost estimate. See the following FHWA letter for a more detailed explanation.  The SI&A form can be requested from a Bridge Inventory Analyst in the Rating Section.  Include a copy of this form in the Layout Folder.
+
===751.1.2.13 Earthquake (Seismic) Consideration===
 +
 +
See [[:Category:756 Seismic Design|EPG 756 Seismic Design]] for flowcharted seismic design requirements.  
  
An interstate job (job no. with an “I” in it) is an example of using federal funds to replace a bridge without worrying about the sufficiency rating of the existing bridgeThe reason this is acceptable is because you are using federal “interstate” funds, not federal “bridge replacement” funds.
+
All new bridge/wall designs must meet Seismic Design Category A requirements which includes nonseismic (or static) designs unless the seismic design category is B, C, or D. If the structure you are laying out falls in Seismic Design Category B, C or D, there are a few items to keep in mind.  Box culverts are preferable to bridges on stream crossings because they are exempt from seismic design unless crossing a known exposed fault.  Pile cap intermediate bents are preferable to open column bents on footings because footings can grow quite large due to seismic forces.  Minimize the number of expansion joints in the deck because each of these locations may require earthquake restrainers which are very costlyMake the superstructure as light as possible, which usually means use steel plate girders or wide flanges instead of prestressed concrete girders wherever possible.  
  
An example of an SIA form can be seen below, followed by a letter from FHWA explaining guidelines for use of federal bridge replacement money.
+
Go to https://earthquake.usgs.gov/designmaps/us/application.php and use the following instructions to determine the LRFD Seismic Design Category:
  
 +
:Instructions:
  
<center>[[Image:751.1_Prelim_Design_SI&A_form_(pg_1).gif]]</center>
+
:1. For “Design Code Reference Document”, '''select''' “Derived from USGS hazard data available in 2002” followed by “2009 AASHTO”.
  
<center>[[Image:751.1_Prelim_Design_SI&A_form_(pg_2).gif]]</center>
+
:2. For “Site Soil Classification”, '''select''' “Site Soil Classification” (Select Site Class “A, B, C, D or E” for preliminary design per Geotechnical Section recommendation or for final design as given on Foundation Investigation Geotechnical Report.
  
 +
:3. For “Site Latitude” and “Site Longitude”, '''input''' coordinates or alternatively '''input''' address or zip code in the map area.
  
<center>[[Image:751.1_Prelim_Design_FHWA_letter_(pg_1).gif]]</center>
+
The new bridge design schedule for a seismic bridge requires 24 months minimum. See [[#751.1.1.5 New Regular Bridge Design Schedule (Nonseismic) (Nonrailway Crossing)|EPG 751.1.1.5 New Regular Bridge Design Schedule]].
<center>[[Image:751.1_Prelim_Design_FHWA_letter_(pg_2).gif]]</center>
 
<center>[[Image:751.1_Prelim_Design_FHWA_letter_(pg_3).gif]]</center>
 
  
===751.1.2.13 Temporary Bridges===
+
===751.1.2.14 Temporary Bridges===
  
 
If the district will be using a bypass on stream crossings, a temporary bridge may be necessary.  The district should first consider using large drainage-diversion pipes to carry the water under the bypass, if the district determines this is not practical, they should submit a Bridge Survey for a temporary bridge on the bypass.  Check with the Structural Project Manager for hydraulic design frequency.
 
If the district will be using a bypass on stream crossings, a temporary bridge may be necessary.  The district should first consider using large drainage-diversion pipes to carry the water under the bypass, if the district determines this is not practical, they should submit a Bridge Survey for a temporary bridge on the bypass.  Check with the Structural Project Manager for hydraulic design frequency.
  
Once the number of 40’ spans has been determined, the district should be contacted so they can locate the pieces necessary for the construction of the bridge.  Make sure the pieces the district intends to use have the “new” beam caps that take 14” H-pile.  The district should provide you with the location of where the pieces are coming from and where they should be taken by the contractor at the end of the project.  If the district is unable to find the pieces, then they will need to be contractor furnished.  This has a big impact on costs. See [[751.1_Preliminary_Design#751.1.2.16_Preliminary_Cost_Estimate|Preliminary Cost Estimate]].
+
Once the number of 40’ spans has been determined, the district should be contacted so they can locate the pieces necessary for the construction of the bridge.  Make sure the pieces the district intends to use have the “new” beam caps that take 14” H-pile.  The district should provide you with the location of where the pieces are coming from and where they should be taken by the contractor at the end of the project.  If the district is unable to find the pieces, then they will need to be contractor furnished.  This has a big impact on costs. See [[751.1_Preliminary_Design#751.1.2.17_Preliminary_Cost_Estimate|Preliminary Cost Estimate]].
 +
 
 +
===751.1.2.15 Bridges Over Railroads===
  
===751.1.2.14 Bridges Over Railroads===
+
Consult the AREMA (American Railway Engineering and Maintenance-of-Way Association) Manual for Railway Engineering located in the Bridge Division’s Development Section for more detailed information. Here are some basic points to keep in mind:
  
Consult the AREA (American Railway Engineers Associations) Manuals located in the Development Section for more detailed information. Here are some basic points to keep in mind:
+
* Railroads often raise their tracks so provide some cushion in your vertical clearance.
 +
* Absolute minimum horizontal clearance shall be 9 feet on each side of track centerline plus 1 1/2 inches per each degree of track curvature. (railroad projects manager of the Multimodal Operations Division will obtain the degree of curvature from the railroad)
 +
* Will the railroad want room for an extra track or maintenance roadway?
 +
* Keep the ballast free drained.  
 +
* Drainage needs to be designed for 100-year storm.
 +
* Slope protection shall consist of Type 2, 18-inch thick rock blanket placed on top of permanent erosion control geotextile. Some railroads may require changes to this; however, this will be determined on a case-by-case basis.
 +
* Some railroads also now require the barrier and slab overhangs to be designed to accommodate fences that may be added in the future.
  
*Railroads often raise their tracks so provide some cushion in your vertical clearance.
+
If the face of the columns of an intermediate bent is within 25 ft. of the centerline of the railroad track, a collision wall is required. If the face of the columns of an intermediate bent is within 12 ft. of the centerline the top of the collision wall shall be set at 12 ft. above top of rail otherwise the top of the collision wall shall be set at 6 ft. above top of rail.  
*Horizontal clearance shall be 12'-0" plus 1.5 inches per each degree of track curvature.  (MoDOT's R.R. liaison will obtain the degree of curvature from the R.R.)
 
*Will the railroad want room for an extra track or maintenance roadway?
 
*Keep the ballast free drained.
 
*Drainage needs to be designed for 100 year storm.
 
*Slope protection shall consist of 1’-6” thick rock blanket (Type 2) placed on top of permanent erosion control geotextile. Some railroads may require changes to this; however, this will be determined on a "case-by-case" basis.
 
*Some railroads also now require the barrier curbs and slab overhangs to be designed to accommodate fences that may be added in the future.
 
  
If the face of the columns of an intermediate bent falls within 25 feet of the centerline of the railroad track, a collision wall is required. The elevation for the top of the collision wall is set at 6 feet above top of rail.
+
The railroad projects manager in the Multimodal Operations Division is a very good resource for answering questions at any stage of the layout. It typically takes a very long time to receive approval of a layout from the railroad. The railroad must approve both the preliminary design and the final plans.
  
The Railroad Liaison in the Multimodal Operations Division is a very good resource for answering questions at any stage of the layout.  It typically takes a very long time to receive approval of a layout from the railroad. The Railroad has to approve both the Preliminary Design and the Final Plans!
+
When making a [[Media:Layout to Railroad.doc|submittal to the railroad project manager]] for approval of the preliminary design, include three sets of half-sized plat and profile sheets, as well as a copy of the Design Layout.
  
When making a [[Media:Layout to Railroad.doc|submittal to the Railroad Liaison]] for approval of the Preliminary Design, include three sets of half-sized plat and profile sheets, as well as a copy of the Design Layout Sheet.
+
The new bridge design schedule for a railway crossing bridge requires 24 months minimum. See [[#751.1.1.5 New Regular Bridge Design Schedule (Nonseismic) (Nonrailway Crossing)|EPG 751.1.1.5 New Regular Bridge Design Schedule]].
  
===751.1.2.15 Historical Bridge Considerations===
+
===751.1.2.16 Historical Bridge Considerations===
  
 
You also need to check with the Historical Bridge Coordinator in the Design Division when replacing a bridge.  There is not a magic age for a bridge for it to become "historical".    Age does not matter.  All "Bridge Resources" that will be impacted by MoDOT need to be cleared through the Department of Natural Resources (DNR) Historic Preservation Program (HPP) before they can be replaced, demolished, extensively rehabilitated or deeded to a new owner (county, city, etc.).  The following is a definition of "Bridge Resources":
 
You also need to check with the Historical Bridge Coordinator in the Design Division when replacing a bridge.  There is not a magic age for a bridge for it to become "historical".    Age does not matter.  All "Bridge Resources" that will be impacted by MoDOT need to be cleared through the Department of Natural Resources (DNR) Historic Preservation Program (HPP) before they can be replaced, demolished, extensively rehabilitated or deeded to a new owner (county, city, etc.).  The following is a definition of "Bridge Resources":
Line 337: Line 439:
 
Usually, bridge resources do not stand in the way of right of way acquisition (A-dates) because they are generally located on roadways that the state already owns; however, there are cases in which bridge resources are privately owned and located on private property.  In these rare cases, bridge resources would need to be checked out prior to our right of way acquisition approval.
 
Usually, bridge resources do not stand in the way of right of way acquisition (A-dates) because they are generally located on roadways that the state already owns; however, there are cases in which bridge resources are privately owned and located on private property.  In these rare cases, bridge resources would need to be checked out prior to our right of way acquisition approval.
  
===751.1.2.16 Preliminary Cost Estimate===
+
===751.1.2.17 Preliminary Cost Estimate===
  
 
The Preliminary Cost Estimate should be neat, legible and dated since a copy of it is included with the Bridge Memo.  It should also be rounded to the nearest thousand dollars.   
 
The Preliminary Cost Estimate should be neat, legible and dated since a copy of it is included with the Bridge Memo.  It should also be rounded to the nearest thousand dollars.   
  
The accepted method of calculating the Preliminary Cost Estimate is to actually calculate some approximate quantities for the bridge and then multiply them by the unit prices supplied by the Review Section.  A spreadsheet should be used to calculate these quantities.  To estimate the pounds of reinforcing steel in a structure, multiply the number of cubic yards of concrete in the structure by 125 for bridges. See table below for Box Culverts.
+
The accepted method of calculating the Preliminary Cost Estimate is to calculate some approximate quantities for the bridge and then multiply them by the unit prices supplied by the Bridge Division Preliminary and Review Section.  A spreadsheet should be used to calculate these quantities.  To estimate the pounds of reinforcing steel in a structure, multiply the number of cubic yards of concrete in the structure by 125 for bridges. See table below for Box Culverts.
 
 
  
:::{|border="1" cellpadding="5" cellspacing="0" style="text-align:center"
+
<center>
 +
{|border="1" cellpadding="5" cellspacing="0" style="text-align:center"
  
|colspan="2"|Box Culvert Reinforcing Steel (lbs.) Estimate
+
!colspan="2" style="background:#BEBEBE" width="400"|Table 751.1.2.17,<br/>Box Culvert Reinforcing Steel (lbs.) Estimate
 
|-
 
|-
|Design Fill (ft.)||Concrete (lbs/cy) Multiplier
+
!style="background:#BEBEBE"|Design Fill (ft.)!!style="background:#BEBEBE"|Concrete (lbs/cy) Multiplier
 
|-
 
|-
 
|2.00||225
 
|2.00||225
Line 360: Line 462:
 
|32.00||84
 
|32.00||84
 
|}
 
|}
 +
</center>
  
 
+
The Preliminary Cost Estimate should be increased for the following items: Cost Estimate Guide for rural preliminary design (do not compound the increases by using your judgment).
The Preliminary Cost Estimate,should be increased for the following items: ([[media:Fig 104.7 (1-02.1) Cost Estimate Guide for Rural Preliminary Design.doc|Cost Estimate Guide for rural preliminary design]] )(do not compound the increases and use your judgment).
 
  
 
:::{|border="0"  
 
:::{|border="0"  
Line 382: Line 484:
  
  
<math>*</math> These factors assume estimated quantities have not been increased due to seismic forces.
+
:::<math>*</math> These factors assume estimated quantities have not been increased due to seismic forces.
  
  
Here are some guidelines for estimating the cost of the removal of existing bridges:
+
Some guidelines for estimating the cost of the removal of existing bridges include:
  
 
:::{|border="0"
 
:::{|border="0"
Line 391: Line 493:
 
|<u>Type of Bridge Removal</u>||<u>Cost per Square Foot</u>
 
|<u>Type of Bridge Removal</u>||<u>Cost per Square Foot</u>
 
|-
 
|-
|Simple Structures Over Streams||align="center"|$ 5
+
|Simple Structures Over Streams||align="center"|**
 
|-
 
|-
|Girder Structures Over Roads||align="center"|$ 7
+
|Girder Structures Over Roads||align="center"|**
 
|-
 
|-
|Conc. Slab Structures Over Interstates||align="center"|$25
+
|Conc. Slab Structures Over Interstates||align="center"|**
 
|-
 
|-
 
|&nbsp; &nbsp;(quick opening of lanes to traffic)
 
|&nbsp; &nbsp;(quick opening of lanes to traffic)
 
|}
 
|}
  
 +
:::<math>**</math>  Consult Bid Tabs for an analysis of the latest bridge removal costs.  Bridge Division staff may consult the Pay Item Spreadsheet maintained by the Structural Preliminary and Review Engineer.
  
After you calculate the Preliminary Cost Estimate, divide it by the area of the deck and compare the price per sq. ft. to this table:
+
===751.1.2.18 Bridge Memorandums===
  
The average costs varyUsually they fall within these ranges.
+
Bridge Memorandums are generated for new and rehabilitated bridge structures including retaining walls. Formal correspondence will not be required for special structural work or miscellaneous structures like high mast tower lighting (HMTL) or small retaining walls equal to or shorter than 5 feet; however, documentation such as a Bridge Memorandum may be a good idea in order to effectively communicate the understanding and agreement to the level of design work proposed and associated construction costs with districts.
 +
   
 +
====751.1.2.18.1 Purpose====
 +
The Bridge Memorandum is the instrument which coordinates bridge plan and roadway plan preparation. It is sent to the district to inform them where we plan to put the bridge, what kind of structure it will be, what the Preliminary Cost Estimate is and any other pertinent information. More information is required on more complicated structures. If you are not sure if the district needs to have a certain piece of information concerning the structure, include it on the Bridge Memorandum to be safe. Too much information is better than too little.
 +
 
 +
An electronic copy of the bridge memorandum and supporting documents are sent to the district for review and signature. If, during the design process, revision to the bridge memorandum by either the district or the Bridge Division becomes necessary, all parties to the memorandum are to be notified immediately. The proposed revisions must be agreed to by all parties that signed the original bridge memorandum.  
  
:::{|border="0"
+
The Bridge Memorandum also serves as a design layout for structures where the latter is not required, see [[#751.1.2.31 Finishing Up Design Layout|EPG 751.1.2.31 Finishing Up Design Layout]].
  
|<u>Type of Bridge</u>||<u>Avg. Price/Sq. Ft. of Deck</u>
+
====751.1.2.18.2 Content====
|-
+
{|style="padding: 0.3em; margin-left:10px; border:2px solid #a9a9a9; text-align:center; font-size: 95%;background:#f5f5f5" width="310px" align="right"
|Prestressed I-Girder||align="center"|$65 - $90
+
|-style="background:#f5f5f5" 
 +
|align-"center"|'''Bridge Memorandum Examples '''
 
|-
 
|-
|Prestressed Bulb-Tee||align="center"|$75 - $100
+
|[[media:751.1.2.18.2 Highway Grade Separation.docx|Highway Grade Separation<br/>(Minor Route over Major Route)]]
 
|-
 
|-
|Plate Girder||align="center"|$90 - $125
+
|[[media:751.1.2.18.2 Railroad Grade Separation 2021.pdf|Railroad Grade Separation<br/>(Minor Route & Priority EQ Route)]]
 
|-
 
|-
|Voided/Solid Slab||align="center"|$90 - $125
+
|[[media:751.1.2.19.2 Stream Crossing Bridge 2021.pdf|Stream Crossing (Bridge)<br/>(Low Volume Route)]]
 
|-
 
|-
|Temp. Bridge (state furn.)||align="center"|$25 - $45
+
|[[media:751.1.2.19.2 Stream Crossing Culvert.pdf|Stream Crossing (Culvert)<br/>(Minor Route)]]
 
|-
 
|-
|Temp. Bridge (cont. furn.)||align="center"|$115 - $145
+
|[[media:751.1.2.18.2 Bridge Rehabilitation 2021.pdf|Bridge Rehabilitation<br/>(Minor Route)]]
 
|-
 
|-
|Major Lake Crossing||align="center"|$175 - $200
+
|[[media:751.1.2.18.2 Bridge Rehabilitation.pdf|Bridge Rehabilitation<br/>(Major Route and Major Bridge)]]
 
|-
 
|-
|Major River Crossing||align="center"|$200 - $250
+
|[[media:751.1.2.19.2 Retaining Wall.pdf|Retaining Wall]]
 
|}
 
|}
  
 +
Sample listing of what to include on the Bridge Memorandum:
 +
 +
1. Identify the following classifications if applicable: (''[[media:751.1.2.18.2 Design Implications.docx|Design Implications]]'')
 +
::• All routes involved shall be classified as either:
 +
:::o ([[media:144 Major Highway System 2022.pdf|major]]), as shown in link.
 +
:::o (minor), not a major route and ADT ≥ 400.
 +
:::o (low volume), not a major route and ADT < 400.
 +
::• Major bridges with a total length ≥ 1000 feet shall be classified by specifying “(major)” behind the specified bridge number.
 +
::• Priority 1 or 2 [http://sp/sites/sm/IRPDocuments/Shared%20Documents/PUBLISHED/ANNEXES/AnnexG_EarthquakePlan/AppendixA-EQEmergencyHwyRoutes.pdf earthquake emergency routes] shall be classified by specifying “(priority <u>1</u> <u>2</u> EQ)” behind the route classification.
 +
 +
2. Identify type of structure, span lengths, skew, loading, roadway width, wing lengths and special end fill considerations.  For curved structures, specify how the design span lengths are to be measured i.e., “measured along the CL of Roadway”. If plate girder or wide flange beam, further identify them as either weathering or painted steel.
 +
 +
3. Indicate all pertinent profile grade, alignment and superelevation transition information.
 +
 +
4. Identify the fill exception stations or ends of the bridge.  The district uses this to coordinate the bridge with their roadway design features such as guardrail. For PSI-Girder bridges, take into account the [[751.22_P/S_Concrete_I_Girders#psi layout length|layout length]] when calculating these stations.
 +
 +
5. Identify slopes at end bents.
 +
 +
6. Indicate elevation of any berms to be constructed at the end bents.
 +
 +
7. If applicable, call for old roadway fill to be removed to natural ground line.
 +
 +
8. For box culverts, indicate the location of the headwalls and the type of wings to be provided (flared or straight).  Also include the upper and lower flow line elevations along the CL of the box.
 +
 +
9. Identify any bridge related items that the district will need to address in their plans or special provisions as a “Roadway Item”.
 +
 +
10. Include the cost estimate for construction (Preliminary Cost Estimate).
 +
 +
11. Include the method of traffic handling while construction is underway.  Attach sketches for staged construction when appropriate.
 +
 +
12. For stream crossings, show all pertinent hydrologic data used for the layout of the structure. See [[751.5 Structural Detailing Guidelines#751.5.2.1.5.3 Hydraulic Data|EPG 751.5.2.1.5.3 Hydraulic Data]] for Hydraulic Data tables.
 +
 +
13. For roadway and railroad grade separations, include all minimum vertical and horizontal clearances (final and construction) and include the opening (horizontal limits) of the minimum vertical clearance. The minimum horizontal clearance shall be specified from the edge of the traveled way(s).
 +
 +
14. Quite often, the district will add items to a bridge late in the final design process because they “didn’t think of them” earlier.  This often causes extra work due to the necessary redesigns.  Include a statement similar to the following to reduce this occurrence:
 +
 +
:*"No conduit, lighting, utility supports or sidewalks are to be included in the final plans for this bridge."
 +
 +
:*If the district has already indicated that they want special items attached to the bridge, include the specifics on the Bridge Memorandum and modify the above note.
 +
 +
15. The design year AADT (annual average daily traffic) and AADTT (annual average daily truck traffic).  Request this from the district if it is not shown on the plat sheet.  On grade separations, get the AADT and AADTT for both roads.
 +
 +
16. For box culverts, always include the following notes:
 +
:*Channel bottom shall be graded within the right of way for transition of channel bed to culvert openings. Channel banks shall be tapered to match culvert openings. (Roadway Item)
 +
:*If any part of the barrel is exposed, the roadway fill shall be warped to provide 12 inches minimum cover. (Roadway Item) (See [[#751.1.2.8.3.3 Roadway Fill|EPG 751.1.2.8.3.3, Box Culverts, Roadway Fill]].)
 +
 +
17. Also for box culverts, state if guardrail (Roadway Item) is to be provided in lieu of meeting the clear zone requirements.  If there will be guardrail over the box culvert and the fill height is less than indicated in [[750.7 Non-Hydraulic Considerations#750.7.4.5 Guardrail Attachment|EPG 750.7.4.5, Box Culverts, Guardrail Attachment]], indicate that attachment of the guardrail to the top slab will be handled in the bridge plans, even though the guardrail itself is a roadway item. For additional information on when to use guardrail attachments, see [[#751.1.2.8.3.2 Length|EPG 751.1.2.8.3.2 Length, Box Culvert, Length]].
 +
 +
18. For stream crossings (new structures, widened structures and rehabs where the waterway opening is reduced.) include a statement stating that a Floodplain Development Permit is required or that a Floodplain Development Permit is not required and that the Bridge Division will request such a permit if necessary. Also indicate the flood hazard zone (i.e., A, A1, B) and whether or not the bridge is in a Floodway.
 +
 +
19. On Rehabilitated and widened structures give the current and proposed load rating and load posting as well as the current condition ratings for the deck, superstructure, substructure and scour.
 +
<div id="19. Identify the bridge"></div>
 +
20. Identify the bridge approach slab class major or minor. If a design exception is required or approved, then note accordingly. Identify asphalt mix type (determined by district) when the asphalt bridge approach slab sub-class is an option. 
 +
 +
21. Identify the bridge end drainage provisions as determined by district Design. For example, note when concrete aprons at each wing wall will be required (Rdwy. Item). Note when concrete approach pavement (Rdwy. Item) with or without drain basins (Rdwy. Item) will be required, or note when rock blanket will be required that extends up to full length of bridge approach slabs, or when drain flumes (Rdwy. Item) will be required.
 +
<div id="21. For redecks or in other cases where"></div>
 +
22. For redecks or in other cases where the rock blanket elevations are not shown on the bridge plans and the top of the rock blanket is required to be flush to the existing ground line in accordance with the Memorandum of Agreement with SEMA, include the following note:
 +
: The top of rock blanket shall be flush to the ground line as directed by the engineer. (Roadway Item.)
  
The cost estimate spreadsheet should be stored at T:\br-proj\current estimates after being reviewed by the Structural Project Manager
+
23. For retaining walls, indicate any aesthetic treatments such as concrete staining and form liner requirements. Be specific regarding names, types and colors of staining, and names and types of form liner.
  
===751.1.2.17 Bridge Memorandums (Memos)===
+
24. Form liners are standard for MSE large block walls. Be specific regarding names, types and colors of staining, and names and types of form liner. See [http://www.modot.org/business/consultant_resources/bridgestandards.htm Bridge Standard Drawings – MSE Wall - MSEW].
  
The [[#bridge memo|Bridge Memo]] is the document sent to the District that tells them where we plan to put the bridge, what kind of structure it will be, the Preliminary Cost Estimate and any other pertinent information. More information is required on more complicated structures.  If you are not sure if the District needs to have a certain piece of information concerning the structure, include it on the Bridge Memo to be safe. Too much information is better than too little.
+
25. For MSE wall abutments: Identify gutter type, fencing, lower longitudinal and lateral drain pipe sizes (type and sizes to be determined by district Design division). (Lateral drain pipes are only required as determined by district Design division.)
  
Here is a sample listing of what to include on the Bridge Memorandum:
+
26. OPTIONAL Seismic Information for new bridge or wall on Memo: Note “Preliminary Seismic Description: Site Class _, Seismic Design Category _, A<sub>s</sub> = __, S<sub>D1</sub> = _” that would require Geotechnical Section input regarding the Site Class and Seismic Design Category used for cost estimating. (This is similar to item no. 9 under [[#751.1.2.31 Finishing Up Design Layout|EPG 751.1.2.31 Finishing Up Design Layout]].)
  
#Identify type of structure, span lengths, skew, loading, roadway width, wing lengths and special end fill considerations.  For curved structures, specify how the design span lengths are to be measured i.e., “measured along the CL of Roadway”.
+
27. For rehabs, redecks, widenings, recoatings and new replacement structures, see [[#751.1.3.9 Environmental Considerations: Asbestos and Lead|EPG 751.1.3.9 Environmental Considerations: Asbestos and Lead]] for notes to include.
#Indicate all pertinent profile grade, alignment and superelevation transition information.
 
#Identify the fill exception stations or ends of the bridge.  The district uses this to coordinate the bridge with their roadway design features such as guardrail. For PSI-Girder bridges take into account the [[751.22_P/S_Concrete_I_Girders#psi layout length|layout length]] when claculating these stations.
 
#Identify slopes at end bents.
 
#Indicate elevation of any berms to be constructed at the end bents.
 
#If applicable, call for old roadway fill to be removed to natural ground line.
 
#For box culverts, indicate the location of the headwalls and the type of wings to be provided (flared or straight).  Also include the upper and lower flow line elevations along the CL of the box.
 
#Identify any bridge related items that the district will need to address in their plans or special provisions as a “Roadway Item”.
 
#Include the cost estimate for construction (Preliminary Cost Estimate).  Include supporting calculations with the Bridge Memo packet sent to the district.
 
#Include the method of traffic handling while construction is underway.  Attach sketches for staged construction when appropriate.
 
#For stream crossings, show all pertinent hydrologic data used for the layout of the structure. See Section [[751.5_Standard_Details#751.5.3_Hydraulics|751.5.3 Hydraulics]] for Hydraulic Data tables.
 
#For grade separations, include all minimum vertical and horizontal clearances (final and construction).  For bridges over railroads, also include minimum lateral clearance from the centerline of track to nearest construction falsework.
 
#Quite often, the district will add items to a bridge late in the final design process because they “didn’t think of them” earlier.  This often causes extra work due to the necessary redesigns. Include a statement similar to the following to reduce this occurrence:  
 
#*"No conduit, lighting, utility supports or sidewalks are to be included in the final plans for this bridge."
 
#*If the district has already indicated that they want special items attached to the bridge, include the specifics on the Bridge Memorandum and modify the above note.
 
#The design year ADT (average daily traffic) and ADTT (average daily truck traffic).  Request this from the district if it is not shown on the plat sheet.  On grade separations, get the ADT and ADTT for both roads.
 
#For box culverts, include the following notes:
 
#*"Provide grading of the channel bottom with the R/W limits as needed for culvert flowline elevations and transition of the channel bed to the culvert openings.  Taper channel banks to match the ends of the culvert opening as required (Roadway Item)."
 
#*"Roadway width is ______ from outside of shoulder to outside of shoulder.  The __ :1 roadway sideslopes are to be ‘rolled up and over’ the culvert to provide minimum cover on the barrel (see road plans)."
 
#*(Use this note when the headwalls are placed to satisfy clear zone requirements and/or when the fill height on top of the culvert is very shallow resulting in a flatter sideslope than that indicated on the roadway typical section).
 
#Also for box culverts, state if guardrail (Roadway Item) is to be provided in lieu of meeting the clear zone requirements.  If there will be guardrail over the box culvert and the fill height is less than 2 feet, indicate that attachment of the guardrail to the top slab will be handled in the bridge plans, even though the guardrail itself is a roadway item.
 
  
Once the Preliminary Designer has the Bridge Memo completed, they should submit it to the Structural Project Manager for their review. The SPM will then request a Bridge Memo Conference with the Assistant State Bridge Engineer and the Structural Resource Manager.  After this review and/or conference, the Preliminary Designer will then proceed with preparing the Bridge Memo package for delivery to the district.
+
====751.1.2.18.3 Supporting Documents====
 +
Supporting documents may provide additional information to the district or request additional information from them. Other documents may need to be included, but at a minimum the following documents should be sent to the district with the Bridge Memorandum:
  
The Bridge Memo should be signed and dated the day you send it out.  You should include spaces for two signatures from the District. When you send the Bridge Memo, you only need to send one copy on white paper. Your original signature should appear on this copy.  
+
:* Calculations used for the [[#751.1.2.17 Preliminary Cost Estimate|Preliminary Cost Estimate]]
The [[Media:Memo to District.doc|cover letter]] accompanying the Bridge Memo should be addressed to the Transportation Project Manager. A cover letter is more desirable than a Letter of Transmittal. The packet sent to the district should include a minimum of the following:
+
:* [[:Category:101 Standard Forms#Constructability Questioinnaire|Constructability Questionnaire]], modify to address project issues
 +
:* Layout for [[#751.1.2.19 Soundings (Borings)|Soundings]]
  
::1 Copy of the [[#bridge memo|Bridge Memo]]
+
====751.1.2.18.4 Bridge Division Review====
::1 Copy of the Calculations used for the Preliminary Cost Estimate
 
::1 Copy of the [[#constructability questionnaire|Constructability Questionnaire]] - (modify to address project issues)
 
::1 Copy of the Layout for Soundings
 
  
Once the signed Bridge Memo is received from the District, one copy should be sent to the State Design Engineer.  Once again it is preferable for a cover letter to be used for this instead of a Letter of Transmittal. The reason for this is that as of December of 1998, you need to include information pertaining to floodplains in this cover letter.  Specifically you need to state whether or not the bridge is in a Floodway or Zone A or other designation. You should also include a statement stating that a [[Media:Memo to Design, Permit Required.doc|Floodplain Development Permit is required]] or that a [[Media:Memo to Design, no Permit Required.doc|Floodplain Development Permit is not required]] and that the Bridge Division will request such a permit if necessary.
+
Once the Preliminary Designer has the Bridge Memo and supporting documents completed, they are submitted to the Structural Project Manager (SPM) for their review. The SPM will then request a Bridge Memo Conference with the Assistant State Bridge Engineer, the Structural Resource Manager and the Structural Prelim. & Review Engineer. After the review and conference, the Preliminary Designer will update the Bridge Memorandum and supporting documents. The Designer and SPM sign and date the memo by typing their names and the date in the locations provided.
  
The original Bridge Memo should be placed in the Layout folder upon its return from the district.
+
====751.1.2.18.5 Bridge/District Agreement Process====
 +
 
 +
The following process will be used to establish agreement between the district and Bridge Division on Bridge Memorandums:
 +
 
 +
:1) Bridge Memorandums and supporting documentation will be made available on SharePoint by Bridge Division.
 +
:2) The Bridge Division preliminary designer or Structural Project Manager (SPM) will email the Transportation Project Manager (TPM) and the District Bridge Engineer a link to the Bridge Memorandum in SharePoint when the memorandum is ready for review by the district. (A link to the Constructability Questionnaire, Cost Estimate, Layout for Soundings, and Request for Soil Properties may also be included.) As part of their review the TPM should forward the Bridge Memorandum to the appropriate Resident Engineer to solicit their input on the Memorandum.
 +
:3) Changes to the Bridge Memorandum should be made in revision mode or with bold blue text for additions and red strikethrough text for deletion of existing text. (Discussion of proposed changes with the Bridge Division preliminary designer and SPM is recommended before making changes.)
 +
:4) Once the district’s review of the Bridge Memorandum is complete the approving district personnel should type their names, titles and the date in the appropriate locations.
 +
:5) TPMs or their designees email the Bridge Division preliminary designer and SPM to inform them the district has reviewed and signed the Bridge Memorandum. A summary explaining any of the changes should be included in the email.
 +
:6) The Bridge Division preliminary designer or SPM will accept the changes or coordinate with TPMs or their designees to resolve any differences.
 +
:7) Once all differences are resolved the Bridge Division preliminary designer or the SPM will email the TPM or the TPM's designee indicating the agreement process is complete. Changes made to the Bridge Memorandum after the initial agreement may be handled by email or by the process described above.
 +
 
 +
====751.1.2.18.6 Documentation====
 +
The Bridge Memorandum, supporting documents and related correspondence will be stored on the Bridge Division SharePoint page in the Projects -Inwork directory.
 +
 
 +
A copy of the agreed upon bridge memo is placed in the Layout folder. If changes are made after the initial agreement, a copy of the revised memo should be added to the layout folder and the original bridge memo marked as void with the date of revision noted.
  
 
<div id="bridge memo"></div>
 
<div id="bridge memo"></div>
 
<center>[[Image:751.1_Prelim_Design_Bridge_Memo_(Ex_1).gif]]</center>
 
<center>[[Image:751.1_Prelim_Design_Bridge_Memo_(Ex_1).gif]]</center>
  
&nbsp;
+
===751.1.2.19 Soundings (Borings)===
&nbsp;
+
{|style="padding: 0.3em; margin-left:10px; border:2px solid #a9a9a9; text-align:center; font-size: 95%; background:#f5f5f5" width="270px" align="right"
&nbsp;
+
|-
 +
|'''Additional Information'''
 +
|-
 +
|[[media:751.1.2.19 Request Jun 30 2021.xlsx|Request for Final Soundings for Structures Form]]
 +
|-
 +
|[[media:751.1.2.19 Guidance Jun 2021.xlsx|Guidance for Request for Final Soundings for Structures Form]]
 +
|}
 +
====751.1.2.19.1 Purpose ====
 +
The borings define subsurface conditions at the project site and are used to determine type of foundation (driven piles, pile cap footing, spread footings, drilled shafts), preliminary estimate of pile lengths and engineering design properties.
  
 +
Note that two types of soundings are typically provided by a soundings investigation.
  
 +
:1. Auger Borings - These are the most typical type of soundings provided due to availability of equipment and low cost. This type of boring is generally stopped immediately upon encountering "hard rock". All description of type of soil and rock encountered is determined in the field.
 +
:2. Core Samples - These are more time consuming and expensive. They are also subject to the availability of the specialized equipment and are therefore provided as sparingly as possible by the soundings crew. Once "hard rock" is encountered at a coring location, drilling is continued for an additional 10 ft. to ensure a consistent layer of actual hard rock (not a boulder). If a void layer is encountered in the additional drilling, the drilling is continued until another 10 ft. of consistent hard rock is encountered. In addition to field determination of soil layer type and performance of the Standard Penetration Test (SPT), samples are returned to the lab for additional tests such as determination of rock quality (% RQD).
  
 +
====751.1.2.19.2 Required Locations====
 +
'''Bridges –''' Borings should be requested at each bent. For bents on columns, estimate the number and location of the columns for each bent and request borings for these locations.
  
<center>[[Image:751.1_Prelim_Design_Bridge_Memo_(Ex_2_Pg_1).gif]]</center>
+
'''Box Culverts –''' Borings should only be requested for Box Culverts on Rock (no bottom slab). Borings should be requested every 10 ft. along the alignment of both exterior walls for single box culverts and along both the exterior and interior walls for multiple cell culverts.
<center>[[Image:751.1_Prelim_Design_Bridge_Memo_(Ex_2_Pg_2).gif]]</center>
 
  
&nbsp;
+
'''MSE Walls –''' Borings should be requested at 25 ft. intervals along the baseline of the MSE Wall and at control points along the wall (such as bend lines). For a MSE Wall that wraps around an end bent, consideration should be given as to whether requesting additional borings in a grid pattern between the walls is necessary.
&nbsp;
 
&nbsp;
 
  
 +
'''CIP Concrete Retaining Walls –''' Borings should be requested at 25 ft. intervals along the wall alignment.
  
 +
====751.1.2.19.3 Required Documents====
 +
'''Plan and Elevation/Profile Sheets.''' Using MicroStation, the proposed structure should be drawn on the bridge survey plan sheet(s). Boring symbols should be placed at all requested boring locations.
  
<div id="constructability questionnaire"></div>
+
To find the Northing and Easting, the "Label Coordinates" tool in MicroStation can be used. The grid factor, projection factor, coordinate system, zone, horizontal datum and vertical datum will be required information necessary for completing the Request for Final Soundings for Structures Form, all of which should have been provided with the bridge survey report.  
<center>[[Image:751.1_Prelim_Design_Constructability_Questionnaire.gif]]</center>
 
  
===751.1.2.18 Soundings (Borings)===
+
'''Plan and Elevation Sheet(s) of Existing Bridge.''' When applicable.
  
The purpose of the borings is to define subsurface conditions at the project site.  This information will be used to determine type of foundation (driven piles, footing, spread footings), preliminary estimate of pile lengths and engineering design properties.
+
'''[[media:751.1.2.19 Request Jun 30 2021.xlsx|Request for Final Soundings for Structures Form]].''' The [[media:751.1.2.19 Guidance Jun 2021.xlsx|Guidance for Request for Final Soundings for Structures Form]] is available.  
  
If boulders or cobbles are indicated, driven piles will need "shoes:, also known as pile point reinforcement.
+
Instructions to Soundings Party included on the form should be similar to the following:
  
If there is a possibility that drilled shafts will be used, request borings based on using drilled shafts so the appropriate lab work can be done the first time.
+
:'''Bridges – '''Provide cores at alternating locations with one core per bent.  Where rock is not encountered at core sampling locations, make standard penetration tests at 5 ft. depth increments.  If rock is encountered at these core locations, provide RQD determinations at 5 ft. depth increments.  If a sounding location is not accessible, please provide an alternative sounding as close as possible to the requested location in order to get an accurate representation of soil conditions at the bent line.
  
Borings should be requested at each bent. For bents on columns, estimate the number and location of the columns for each bent and request borings for these locations. Cores should be taken at each station, alternating locations at the field party’s discretion.  Each boring should be taken to rock, or 30’ into material with a blow count of 20 or higher.
+
:'''Box Culverts –''' Provide cores at each location to determine depth and quality of rock. Information will be used to determine structure type (concrete box on rock – without bottom slab) and excavation quantities. If rock is unsuitable for concrete box on rock, discontinue core and sound depth to rock. If sounding location is not accessible, provide an alternate sounding as close as possible to the requested location in order to get an accurate representation of soil conditions along proposed culvert wall.
  
Completed standard forms shall be sent to the Construction and Materials Division to request soundings. This is typically done at the same time that the Bridge Memo is sent to the District. The packet sent to the district should include a minimum of the following: (Consultants should contact Structural Liaison Engineer)
+
:'''Retaining Walls -''' Request that soundings be taken every 25 ft. along the wall alignment. Soundings shall be made to rock or to a point which is 20 ft. below the bottom of the wall, whichever is higher.
  
::1 Copy of the [[#request for final soundings|Request for Final Soundings]] of Structure
+
'''Request for Soil Properties –''' The request for soil properties is located on a separate tab in the Request for Final Soundings for Structures form.
::2 Copies of the [[#soundings layout|Soundings Layout]]
 
::2 Copies of the [[#request for soil properties|Bridge Unit Request for Soil Properties]]
 
::2 Copies of the Plat and Profiles Sheets (half-sized)
 
::2 Copies of Sheet 1A of the Existing Bridge Plans (if applicable)
 
  
In addition, an email should be sent to the Geotechnical Engineer and Geotechnical Director in Construction and Materials Division.  This email should have the electronic files of the three standard forms attached.
+
:'''Bridges –''' If there is a possibility that drilled shafts will be used, request borings based on using drilled shafts so the appropriate lab work can be done the first time.
  
 +
:'''MSE Walls –''' The request for soundings for MSE walls should include requests for the angle of internal frictions (Ø) for both the foundation and the retained material.
  
<div id="request for final soundings"></div>
+
'''Due Date –''' Use the following guidelines when setting a due date:
<center>[[Image:751.1 Prelim Design request for final soundings.gif]]</center>
 
  
 +
<center>
 +
{| border="1" class="wikitable" style="margin: 1em auto 1em auto" style="text-align:center"
 +
|+
 +
! style="background:#BEBEBE" |Project Time Line!! style="background:#BEBEBE" |Foundation Report Due Date
 +
|-
 +
|< 10 Months|| Contact Geotechnical Section<sup>'''1'''</sup>
 +
|-
 +
|≥ 10 Months|| 13 Weeks from Submittal Date
 +
|-
 +
|colspan="2" width="750" align="left"|<sup>'''1'''</sup> Preferred due date should be discussed at the memo conference and the Geotechnical Section contacted to establish a due date.
 +
|}
 +
</center>
 +
 +
====751.1.2.19.4 Submittal====
 +
The completed Request for Final Soundings of Structures form and the other supporting documents listed above should be stored on the Bridge Division SharePoint page in the [http://sharepoint/systemdelivery/BR/projects/default.aspx Projects-Inwork directory] under the structure’s subfolder. (Consultants should contact the Structural Liaison Engineer).
 +
 +
A request for soundings should be sent by email to the Construction and Materials Division. The email shall be addressed to the Geotechnical Engineer and copied to the Geotechnical Director and the Structural Project Manager (or the Structural Liaison Engineer). It should include at a minimum, a link to the SharePoint folder that contains the completed Request for Final Soundings of Structures Form and supporting documents. In addition to the SharePoint link, any relevant information that may aid the Geotechnical Section in providing the requested borings should be included.
  
 +
The request for soundings is typically done at the same time that the Bridge Memorandum is sent to the district.
  
 +
===751.1.2.20 Substructure Type===
  
<div id="soundings layout"></div>
+
Once the signed Bridge Memo and the Borings are received, the entire layout folder should be given to the Preliminary Detailer (requested by SPM, assigned by Structural Resource Manager). The Preliminary Detailer will copy the appropriate MicroStation drawings into their own directory.  (Do not rename files) Consultants contact Structural Liaison Engineer.  The Preliminary Detailer will then draw the proposed bridge on the plat and profile sheets.  The bridge should also be drawn on the contracted profile for a perspective of the profile grade relative to the ground line for drainage considerations.  The Preliminary Detailer will also generate a draft Design Layout Sheet and then return the layout folder to the Preliminary Designer for review.
<center>[[Image:751.1 Prelim Design soundings layout.gif]]</center>
 
  
 +
The Preliminary Designer will then choose the substructure types for each of the bents. Pile cap bents without concrete encasement are less expensive than column bents but they should not be used at the following locations:
  
 +
:Where drift has been identified as a problem 
  
 +
:Where the height of the unbraced piling is excessive and kl/r exceeds 120 (kl/r<120 is generally preferred) (take scour into account)
  
<div id="request for soil properties"></div>
+
:Where the bent is adjacent to traffic (grade separations)
  
===751.1.2.19 Substructure Type===
+
Encased pile cap bents may be considered if economical. Embed concrete encasement 2 ft. (minimum) below the top of the lowest finished groundline elevation, unless a greater embedment is required for bridge scour.  Greater embedment up to 5 or 6 ft. may be considered in situations where anticipated ground line elevation can fluctuate more severely.  (Be sure to account for excavation quantities for deeper embedment.)  Provision for encasing piles may be considered at the following locations:
  
Once the signed Bridge Memo and the Borings are received, the entire layout folder should be given to the Preliminary Detailer (requested by SPM, assigned by Structural Resource Manager).  The Preliminary Detailer will copy the appropriate Microstation drawings into their own directory.  (Do not rename files) Consultants contact Structural Liaison Engineer.  The Preliminary Detailer will then draw the proposed bridge on the plat and profile sheets and add the borings to the profile sheets.  The bridge should also be drawn on the contracted profile for a perspective of the profile grade relative to the ground line for drainage considerations.  The Preliminary Detailer will also generate a draft Design Layout Sheet and then return the layout folder to the Preliminary Designer for review.
+
:Where drift is a concern and protection is required
  
The Preliminary Designer will then choose the substructure types for each of the bents.  Pile cap bents are less expensive than column bents but they should not be used in the following locations;
+
:Where larger radius of gyration is necessary and therefore improved buckling resistance for locations where the exposed unbraced column length is large
*Where drift has been identified as a problem. *
 
*Where the height of the unbraced piling is excessive (<math>\, kl/r < 120</math> is a general rule of thumb) (take scour into account). *
 
*Where the bent is adjacent to traffic (grade separations).
 
  
{|border="0"
+
:Not exclusively where the piles at the pile/wall interface may experience wet/dry cycles and/or excessive periods of ground moisture
|* Consider encasing the piling in concrete to allow a pile cap bent.
 
|}
 
  
 
<div id="top of permanent casing elevation"></div>
 
<div id="top of permanent casing elevation"></div>
 
For column bents, an economic analysis should be performed to compare drilled shafts to footings with cofferdams.  When evaluating the drilled shaft option, keep in mind that if casing is used (see Geotechnical information) it should extend at least as high as the elevation that would be used for the seal course design.  Also keep in mind that the permanent casing should be kept at least one foot below the ground line or low water elevation.  Any casing above this elevation will be temporary.
 
For column bents, an economic analysis should be performed to compare drilled shafts to footings with cofferdams.  When evaluating the drilled shaft option, keep in mind that if casing is used (see Geotechnical information) it should extend at least as high as the elevation that would be used for the seal course design.  Also keep in mind that the permanent casing should be kept at least one foot below the ground line or low water elevation.  Any casing above this elevation will be temporary.
  
End Bents are usually pile caps; however, if quality rock is abundant at or just below the bottom of beam elevation, a stub end bent on spread footings may be used.  If you have any doubt about the suitability and uniformity of the rock, you can still use a pile cap end bent.  Just include prebore to get a minimum of 10 feet of piling into the rock.  If you have concerns about temperature movements, you can require that the prebore holes be oversized to allow for this movement.
+
End Bents are usually pile cap bents; however, if quality rock is abundant at or just below the bottom of beam elevation, a stub end bent on spread footings may be used.  If you have any doubt about the suitability and uniformity of the rock, you can still use a pile cap end bent.  Just include prebore to get a minimum of 10 ft. of piling.  If you have concerns about temperature movements, you can require that the prebore holes be oversized to allow for this movement.
  
Once the substructure type has been determined, re-examine your preliminary cost estimate and notify the district if it needs to be adjusted.
+
For any pile cap bents, where steel piles are to be placed near a fluctuating water line or near a ground line where aggressive soil conditions exist or anticipated to exist in the future, corrosion can result in substantial material loss in pile sections over time, either slowly or rapidly. Galvanized steel piling is required for all new pile cap bents to be used as a deterrent to both accelerated and incidental pile corrosion as commonly seen in the field. Further, conditions like known in corrosive soils, some stream crossings with known history of effects on steel piles and grounds subject to stray currents, these conditions should affect the decision of whether pile cap bents can be effectively utilized. The potential effects of corrosion and the potential deterioration from environmental conditions should always be considered in the determination and selection of the steel pile type and steel pile cross-section (size of HP pile or casing thickness), and in considering the long-term durability of the pile type in service.  
  
===751.1.2.20 Type of Footings===
+
Once the substructure type has been determined, re-examine your Preliminary Cost Estimate and notify the district if it needs to be adjusted.
  
Once it has been determined that a bent will have columns on footings, the next decision is whether the footings should be pile or spread (on shale or rock).  If it is a stream crossing, the bottom of footing elevation should be based on the scour calculations found in the [[750.3_Bridges|Hydraulic Design]] section.  The borings should then be studied to see if a minimum of 10' of piling can be placed below the footings.  If this is doubtful because of the presence of shale or rock, spread footings or drilled shafts should be used.  In instances where it appears that a spread footing can be used but there are pinnacles in the area, you may want to use a pile footing and just require prebore to insure that you get the minimum embedment of 10 feet.  For spread footings on grade separations, include a “not above” elevation to ensure a footing cover of at least 3 feet.
+
'''Galvanized Steel Piles'''
  
Note that two types of soundings are typically provided by a sounding investigation.
+
Galvanizing shall be required for all steel piles. Utilizing galvanized steel piles and pile bracing members shall be in addition to the requirements of [https://www.modot.org/missouri-standard-specifications-highway-construction#page=13 Standard Specifications Sec 702] except that protective coatings specified in Sec 702 will not be required for galvanized piles or galvanized bracing members.  
  
#Auger Borings - These are the most typical type of sounding provided due to availability of equipment and low cost. This type of boring is generally stopped immediately upon encountering "hard rock".  All description of type of soil and rock encountered is determined in the field.
+
Where galvanized steel piling is expected to be exposed to <u>severe</u> corrosive conditions, consideration can be given to increased steel pile thickness or consideration of a reduced loaded steel area for bearing, or conditions mitigated to prevent long term corrosivity risk . This equally applies to the potential corrosion and early deterioration of permanent steel casing used for drilled shafts though they are not required to be galvanized. For all cases, further consideration beyond normal practice should be given to investigating corrosion protection, rate of corrosion as it relates to steel thickness design and expected service life including galvanizing losses, corrosion mitigation or different substructure support in order to meet a 75 year or longer design life. For additional information refer to LRFD 10.7.5 and 10.8.1.5. Consult with the Structural Project Manager or Structural Liaison Engineer to determine options and strategy for implementation.  
#Core Samples - These are more time consuming and expensive. They are also subject to the availability of the specialized equipment and are therefore provided as sparingly as possible by the sounding crew.  Once "hard rock" is encountered at a coring location, drilling is continued for an additional 10 feet to ensure a consistent layer of actual hard rock (not a boulder). If a void layer is encountered in the additional drilling, the drilling is continued until another 10 feet of consistent hard rock is encountered. In addition to field determination of soil layer type and performance of the Standard Penetration Test (SPT), samples are returned to the lab for additional tests such as determination of rock quality (% RQD).
 
  
===751.1.2.21 Types of Piling===
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'''All Bridge and Retaining Wall Piles (For Example, abutment piles, wing wall piles, intermediate pile cap bent piles and pile cap footing piles)'''
  
The two types of piling commonly used are H-pile or pipe pile (cast-in-place, CIP). H-piles are commonly used when shale or rock will be encountered at an elevation that will limit the pile lengths to about 100’. CIP piles are commonly used as friction pile. Use shoes (pile point reinforcement) if boulders or cobbles are anticipated. Prebore if necessary to achieve minimum embedment.
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All surfaces of piles shall be galvanized to a minimum galvanized penetration (elevation) or its full length based on the following guidance. The minimum galvanized penetration (elevation) shall be estimated in preliminary design and finalized in final design. The minimum galvanized penetration (elevation) or full length will be shown on the design layout.
  
 +
Guidance for determining minimum galvanized penetration (elevation):
 +
 +
The designer shall establish the limits of galvanized structural steel pile (i.e., HP pile and CIP pile).  All exposed pile plus any required length below ground shall be galvanized. Based on required galvanized pile length determine and show Minimum Galvanized Penetration (Elevation) or Full Length on the Design Layout and on the plans.
 +
<div id="Required Pile Length"></div>
 +
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 +
|-
 +
!style="background:#BEBEBE" width="150"| !!style="background:#BEBEBE"|Required Pile<br/>Galvanizing<br/>For Nonscour!!style="background:#BEBEBE" width="200"|Required Pile<br/>Galvanizing<br/>For Channel Scour !!style="background:#BEBEBE" width="200"|Required Pile<br/>Galvanizing<br/>For Channel Migration
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|-
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|align="center"|Estimated Pile Length ≤ 50 feet||align="center"|Full Length of Pile||align="center"| Full Length of Pile||align="center"| Full Length of Pile
 +
|-
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|align="center"|Estimated Pile Length > 50 feet ||align="center"|20 feet (in ground)<sup>'''1'''</sup> ||align="center"| 20 feet (in ground)<sup>'''1'''</sup>, but not less than 5 feet below max. scour depth.||align="center"| 20 feet (in ground)<sup>'''1'''</sup>, but not less than 5 feet below stream bed elev.
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|-
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|colspan="4"|<sup>'''1'''</sup>  “In ground” is measured from finished ground line on intermediate bents, and bottom of beam cap for abutments.
 +
|}
 +
<div id="For retaining walls supported"></div>
 +
For retaining walls supported on piles, the minimum galvanized penetration (elevation) for piles shall be “Full Length of Pile” for estimated pile length up to 50 feet and 15 feet below bottom of wall for estimated pile length greater than 50 feet.
 +
 +
For bridge end bents on piles with embankments supported by MSE walls, the minimum galvanized penetration (elevation) for piles shall be “Full Length of Pile” for estimated pile length up to 50 feet and 15 feet below top of leveling pad for estimated pile length greater than 50 feet.
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 +
'''Temporary Bridge Piles'''
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 +
Protective coatings are not required in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction#page=13 Sec 718]. Galvanized pile is not required. All HP piles driven to rock shall require pile point reinforcement.
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===751.1.2.21 Type of Footings===
 +
 +
Once it has been determined that a bent will have columns on footings, the next decision is whether the footings should be pile or spread (on shale or rock).  If it is a stream crossing, the bottom of footing elevation should be based on the scour calculations found in [[750.3_Bridges|EPG 750.3 Bridges]], an article dealing with hydraulic design.  The borings should then be studied to see if a minimum of 10 ft. of piling can be placed below the footings.  If this is doubtful because of the presence of shale or rock, spread footings or drilled shafts should be used.  In instances where it appears that a spread footing can be used but there are pinnacles in the area, you may want to use a pile footing and just require prebore to ensure that you get the minimum embedment of 10 feet.  For spread footings on grade separations, include a “not above” elevation to ensure a footing cover of at least 3 feet.
 +
 +
===751.1.2.22 Types of Piling===
 +
 +
The two types of piling commonly used are structural steel HP pile and close-ended steel pipe pile (cast-in-place, CIP). Open ended steel pipe pile (cast-in-place, CIP) can also be used. HP piles are commonly used as end bearing piles when shale or rock will be encountered at an elevation that will limit the pile lengths to about 100 ft. or less. CIP piles are commonly used as friction pile for which a minimum tip elevation must be determined (see [[751.36 Driven Piles#751.36.2 Steel Pile|EPG 751.36.2 Steel Pile]] for criteria). All HP piles driven to rock shall require pile point reinforcement. For CIP pile, Geotechnical Section indicates either "No Pile Point Needed" or "Pile Point Needed" and recommends pile point type on boring log. “Cruciform” or “Conical” pile point reinforcement is allowed for closed ended CIP pile. “Manufactured open ended cutting shoe (inside flange)” pile point reinforcement is allowed for open ended CIP. Generally pile point reinforcement is needed for CIP pile if boulders, cobbles or dense gravel are anticipated. For all piles, prebore if necessary to achieve minimum embedment.
  
 
Here are some guidelines for minimum embedment:
 
Here are some guidelines for minimum embedment:
  
  
 +
<center>
 
::{|border="1" cellpadding="5" cellspacing="0" style="text-align:center"
 
::{|border="1" cellpadding="5" cellspacing="0" style="text-align:center"
  
|'''Pile Type'''||'''Location'''||'''Minimum Embedment'''
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|width="240"|'''Pile Type'''||width="500"|'''Minimum Embedment'''
 +
|-
 +
|width="240"|Structural Steel HP-Pile||width="500"|10' into natural ground <br/>15’ into natural ground at integral end bents<sup>(1)(2)</sup><br/>10’ below bottom of MSE wall leveling pad<br/> 15'-20' below scour depth<sup>(4)</sup>
 
|-
 
|-
|Steel H-Pile||All||10' into natural ground <br/> 15'-20' below scour depth*
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|width="240"|CIP Steel Pipe Pile||width="500"|10' into natural ground <br/> 10’ below bottom of MSE wall leveling pad<br/>15’ into natural ground at integral end bents<sup>(1)(3)</sup><br/>15'-20' below scour depth<sup>(4)</sup>
 
|-
 
|-
|CIP Pile||All||10' into natural ground <br/> 15'-20' below scour depth*
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|colspan="2" align="left" width="740"|'''(1)''' 10’ is allowed if piles are designed using a rigorous design procedure.<br/>'''(2)''' When precore into rock is necessary to provide the minimum 15’ embedment, a minimum precore of 5’ is required. (i.e., 12’ of soil over rock will require a 17’ pile embedment)<br/>'''(3)''' When prebore is required, pile shall be embedded at least 15’ below prebore hole.<br/>'''(4)''' 15’ if the material is hard cohesive or dense granular; 20’ if the material is soft cohesive or loose granular.
 
|}
 
|}
 +
</center>
  
  
{|border="0"
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See [[751.24 LFD Retaining Walls#751.24.2.1 Design|EPG 751.24.2.1 Design]] for further guidance on pile embedment behind MSE Walls.
 
 
|valign="top"|*||15’ If the material is hard cohesive or dense granular; 20’ if the material is soft cohesive or loose granular.
 
|}
 
  
===751.1.2.22 Estimating the Lengths of Piles===
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===751.1.2.23 Estimating the Lengths of Piles===
  
All designers doing preliminary design should use the DRIVEN computer program to estimate the lengths for piling.
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All designers doing preliminary design should use the bearing graph provided in the foundation investigation Geotechnical report to estimate the lengths for piling.  If a bearing graph is not provided the designer should perform a static analysis.
  
One way to check the validity of your DRIVEN results is to look at the piling information for existing bridges in the vicinity. Please also be on the lookout for any borings that contain "glacial till" (gravelly clay). This material is notorious for stopping pile.
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One way to check the validity of your static analysis results is to look at the piling information for existing bridges in the vicinity. Please also be on the lookout for any borings that contain "glacial till" (gravelly clay). This material is notorious for stopping pile.  
  
 
This procedure is not a substitute for experience and engineering judgment.  It is simply an attempt to have a more uniform method for estimating pile lengths.
 
This procedure is not a substitute for experience and engineering judgment.  It is simply an attempt to have a more uniform method for estimating pile lengths.
Line 590: Line 805:
 
All soil data must be obtained as well as elevation information pertaining to intermediate and end bents.  The soil borings and core information are then observed.  The unit weights of the different soil layers are determined by correlating information from the core data with information found in reference tables.  The resulting unit weights are written on the soil boring page.  If the soil is cohesive, the undrained shear strength should be determined by dividing the results of the pocket penetrometer test by two.  If there was no pocket penetrometer test performed, then a correlation between the SPT blow counts and the undrained shear strength can be determined from reference tables.  The water table must be identified or estimated and labeled on each of the borings and cores.  The water table is usually distinguishable by the presence of gray colored soil. Note that more accurate data is obtained from cores than is obtained from borings because borings are performed using an auger type apparatus that mixes and remolds the soil.
 
All soil data must be obtained as well as elevation information pertaining to intermediate and end bents.  The soil borings and core information are then observed.  The unit weights of the different soil layers are determined by correlating information from the core data with information found in reference tables.  The resulting unit weights are written on the soil boring page.  If the soil is cohesive, the undrained shear strength should be determined by dividing the results of the pocket penetrometer test by two.  If there was no pocket penetrometer test performed, then a correlation between the SPT blow counts and the undrained shear strength can be determined from reference tables.  The water table must be identified or estimated and labeled on each of the borings and cores.  The water table is usually distinguishable by the presence of gray colored soil. Note that more accurate data is obtained from cores than is obtained from borings because borings are performed using an auger type apparatus that mixes and remolds the soil.
  
===751.1.2.23 Drilled Shafts===
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===751.1.2.24 Drilled Shafts===
  
 
Drilled shafts are to be used when their cost is comparable to that of large cofferdams and footings.  Other examples include when there are subsurface items to avoid (culverts, utilities, etc.) or when there are extremely high soil pressures due to slope failures.   
 
Drilled shafts are to be used when their cost is comparable to that of large cofferdams and footings.  Other examples include when there are subsurface items to avoid (culverts, utilities, etc.) or when there are extremely high soil pressures due to slope failures.   
Line 598: Line 813:
 
Cost estimate savings and supporting subsurface information shall be discussed with Construction and Materials before permanent casing is omitted on a project.
 
Cost estimate savings and supporting subsurface information shall be discussed with Construction and Materials before permanent casing is omitted on a project.
  
The borings report for drilled shafts should supply you with the allowable end bearing and side friction as well as the elevations for which the allowable rock values are applicable.   
+
The Foundation Investigation Geotechnical Report (or soundings report) for drilled shafts should supply you with the nominal end bearing (tip resistance) and side friction (side resistance) as well as the elevations for which the nominal rock values are applicable.   
  
 
The Design Layout Sheet should include the following information:
 
The Design Layout Sheet should include the following information:
  
:Top of Shaft Elevation  
+
:Top of Drilled Shaft Elevation  
 
:[[#top of permanent casing elevation|Top of Permanent Casing Elevation]]
 
:[[#top of permanent casing elevation|Top of Permanent Casing Elevation]]
:Top of Sound Rock Elevation
+
:Anticipated Tip of Casing Elevation
 +
:Anticipated Top of Sound Rock Elevation
  
  
Line 614: Line 830:
 
|}
 
|}
  
===751.1.2.24 Excavation Datum===
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===751.1.2.25 Excavation Datum===
  
 
An Excavation Datum should be placed on the Layout Sheet when water is expected to be encountered during the excavation for footings.  The elevation used is usually the Low Water Elevation plus 1 foot (rounded up to the next even foot) but may be made slightly higher on bigger streams and rivers.  Everything above this datum is Class 1 Excavation while everything below it is Class 2 Excavation.
 
An Excavation Datum should be placed on the Layout Sheet when water is expected to be encountered during the excavation for footings.  The elevation used is usually the Low Water Elevation plus 1 foot (rounded up to the next even foot) but may be made slightly higher on bigger streams and rivers.  Everything above this datum is Class 1 Excavation while everything below it is Class 2 Excavation.
  
===751.1.2.25 Seal Courses===
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===751.1.2.26 Seal Courses===
  
 
On structures over water with pile footings, a determination should be made as to whether or not to include seal courses.  Seal courses are used in conjunction with cofferdams when a contractor may have trouble dewatering the footing excavation.  They are usually necessary when you have sandy or gravelly soils and footing elevations below the stream bed.  You will need to include a water surface elevation on the Design Layout Sheet for which the Seal Courses should be designed for.  Typically the elevation used is the average of the Low Water Elevation and the Design High Water Elevation; however, a site visit may be required to determine how reasonable this is.  In no case should this elevation be higher than the 10 year high water elevation or the overbank elevation.
 
On structures over water with pile footings, a determination should be made as to whether or not to include seal courses.  Seal courses are used in conjunction with cofferdams when a contractor may have trouble dewatering the footing excavation.  They are usually necessary when you have sandy or gravelly soils and footing elevations below the stream bed.  You will need to include a water surface elevation on the Design Layout Sheet for which the Seal Courses should be designed for.  Typically the elevation used is the average of the Low Water Elevation and the Design High Water Elevation; however, a site visit may be required to determine how reasonable this is.  In no case should this elevation be higher than the 10 year high water elevation or the overbank elevation.
  
===751.1.2.26 Cofferdams===
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===751.1.2.27 Cofferdams===
  
Cofferdams should be included if the depth of the hole for the footing exceeds 8 feet and/or the bottom of footing elevation is below the Ordinary High Water (OHW) elevation.  Any bent that requires a seal course will also require a cofferdam.  These are bid lump sum per bent.     Consult with the Assistant State Bridge Engineer about this.  All piling in pile footings should be straight (not battered) when a cofferdam is expected.
+
Cofferdams should be included if the depth of the hole for the footing exceeds 8 feet and/or the bottom of footing elevation is below the Ordinary High Water (OHW) elevation.  Any bent that requires a seal course will also require a cofferdam.  These are bid lump sum per bent. Consult with the Assistant State Bridge Engineer about this.  All piling in pile footings should be straight (not battered) when a cofferdam is expected.
  
===751.1.2.27 Webs===
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===751.1.2.28 Webs===
  
 
On structures over water where medium to heavy drift has been indicated on the Bridge Survey, consider using web walls between the columns on the column bents near or in the stream.  The bottom elevation for the web is typically 1' higher than the overbank elevation.
 
On structures over water where medium to heavy drift has been indicated on the Bridge Survey, consider using web walls between the columns on the column bents near or in the stream.  The bottom elevation for the web is typically 1' higher than the overbank elevation.
  
===751.1.2.28 Protection of Spill Slopes===
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===751.1.2.29 Protection of Spill Slopes and Side Slopes===
  
The District shall be consulted for type of slope protection.  Concrete Slope Protection is a Roadway Pay Item.  On stream crossings, Rock Blanket is usually placed.  The type and thickness of Rock Blanket is to be determined by the District based on the flow velocity from the Design High Water.  This flow velocity is determined by the person doing the hydraulic calculations and should be placed on the Bridge Memo.
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The district shall be consulted for type of slope protection.  Either Concrete Slope Protection or Rock Blanket can be used for grade separations and are Roadway Pay Items.  On stream crossings, Rock Blanket is usually placed.  The type and thickness of Rock Blanket is to be determined by the district based on the flow velocity from the [https://epg.modot.org/index.php?title=750.3_Bridges#750.3.1.9_Scour Scour] design flood frequency.  This flow velocity is determined by the person doing the hydraulic calculations and should be placed on the Bridge Memorandum. Permanent erosion control geotextile is always required to be placed under rock blanket.
  
 
When Rock Blanket is used, an elevation for the upper limit of this protection needs to be calculated.  First, calculate the following two elevations:
 
When Rock Blanket is used, an elevation for the upper limit of this protection needs to be calculated.  First, calculate the following two elevations:
Line 643: Line 859:
 
If the toe of the abutment slope falls on the overbank, the rock blanket apron should extend from the toe toward the channel a distance equal to twice the 100 year flow depth on the overbank, but need not exceed 25 feet.
 
If the toe of the abutment slope falls on the overbank, the rock blanket apron should extend from the toe toward the channel a distance equal to twice the 100 year flow depth on the overbank, but need not exceed 25 feet.
  
===751.1.2.29 Design Exceptions===
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Note: District Design has the option of extending rock blanket up to and for the full length of the bridge approach slab or otherwise using drain flumes for bridge end drainage. See [[:Category:503 Bridge Approach Slabs|EPG 503 Bridge Approach Slabs]], [[:Category:611 Embankment Protection|EPG 611 Embankment Protection]] and [https://www.modot.org/media/16882 Standard Plan 609.40].
 +
 
 +
===751.1.2.30 Design Exceptions===
  
Anytime MoDOT standards are not followed, a Design Exception is necessary. These are usually initiated by the Transportation Project Manager in the district; however, if the item is related to the bridge, the Bridge Division will initiate the [[131.4 Design Exception Process|Design Exception]].
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Anytime MoDOT standards are not followed, a Design Exception is necessary. These are usually initiated by the Transportation Project Manager in the district; however, if the item is related to the bridge, the Bridge Division will initiate the [[131.1 Design Exception Process|Design Exception]].
  
The [http://epg.modot.mo.gov/forms/DE-DEForms/DESIGN%20EXCEPTION%20INFORMATION.dot Design Exception Information Form] should be filled out by the preliminary designer and then reviewed by the Structural Project Manager (SPM). A complete explanation of the basis for the design variance must be provided, including cost justification and details on how the variance will affect adjacent properties. The SPM should then submit the Design Exception to the Assistant State Bridge Engineer for review. After this review, the Design Exception should be submitted to the State Bridge Engineer for his signature. This submission should include written comments from the SPM on why the Design Exception should be approved. Once the Design Exception has been signed by the State Bridge Engineer, the SPM should mail the [http://epg.modot.mo.gov/forms/DE-DEForms/DESIGN%20EXCEPTION%20INFORMATION.dot Design Exception Information Form] and [[Media:Design Except to District.doc|cover letter]] to the Transportation Project Manager in the district. The TPM will sign it and then send it to the General Headquarters Design Division for final approval.  The Design Division will supply copies of the signed Design Exception to both the district and the Bridge Division.
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The [[media:131.1 Design Exception 2020.docx|Design Exception Information]] should be filled out by the preliminary designer and then reviewed by the Structural Project Manager (SPM). A complete explanation of the basis for the design variance must be provided, including cost justification and details on how the variance will affect adjacent properties. The SPM should then submit the Design Exception to the Assistant State Bridge Engineer for review. After this review, the Design Exception should be submitted to the State Bridge Engineer for the Sate Bridge Engineer's signature. This submission should include written comments from the SPM on why the Design Exception should be approved. Once the Design Exception has been signed by the State Bridge Engineer, the SPM should mail the [[media:131.1 Design Exception 2020.docx|Design Exception Information Form]] and [[Media:Design Except to District.doc|cover letter]] to the Transportation Project Manager in the district. The TPM will sign it and then send it to the General Headquarters Design Division for final approval.  The Design Division will supply copies of the signed Design Exception to both the district and the Bridge Division.
  
 
Some examples of Design Exceptions initiated by the Bridge Division are:
 
Some examples of Design Exceptions initiated by the Bridge Division are:
Line 669: Line 887:
 
'''Roadway/Shoulder Width Less Than Standard (Existing Structures)'''
 
'''Roadway/Shoulder Width Less Than Standard (Existing Structures)'''
  
On Non-Interstate Rehab (3R) jobs, an exception for width is required any time we don’t meet the new design standards.  The approach lanes being referred to in the [[media:128 3R Design Standards (Rural).doc|rural design standards note (8)]] are the new lanes.  The last note should be modified to read “Bridges programmed for replacement within 5 years may be allowed to remain in place as is and should be looked at on a case by case basis.”
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On Non-Interstate Rehab (3R) jobs, an exception for width is required any time we don’t meet the new design standards.  The approach lanes being referred to in the [[media:128 3R Design Standards (Rural) 2013.docx|rural design standards note (8)]] are the new lanes.  The last note should be modified to read “Bridges programmed for replacement within 5 years may be allowed to remain in place as is and should be looked at on a case by case basis.”
 
   
 
   
On Interstate Rehab (4R) jobs, an exception for width is required any time we don’t meet the [[new design standards]].  If an existing bridge is over 200 feet long, FHWA has said that they will routinely approve the width if both shoulders are at least 3.5’ wide, but we should still request the Design Exception.  FHWA will want to see any approved Design Exceptions before they approve the preliminary design.
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On Interstate Rehab (4R) jobs, an exception for width is required any time we don’t meet the new design standards.  If an existing bridge is over 200 feet long, FHWA has said that they will routinely approve the width if both shoulders are at least 3.5’ wide, but we should still request the Design Exception.  FHWA will want to see any approved Design Exceptions before they approve the preliminary design.
  
===751.1.2.30 Finishing Up Design Layout===
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'''Bridge Approach Slabs (New Bridges)'''
 +
 
 +
On new bridges, the interchangeability of bridge approach slab classes will require a design exception. For example, if a Bridge Approach Slab (Major) is to be substituted for a Bridge Approach Slab (Minor), a design exception will be required and initiated by the Bridge Division based on project core team consensus.
 +
 
 +
===751.1.2.31 Finishing Up Design Layout===
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 +
Design Layouts shall be generated for new bridges, retaining walls and when foundation work is required for bridge widenings.  Otherwise, Design Layouts are not utilized for conveyance of information related to rehabilitation projects, or work on existing bridges or, more generally, on structures.
  
 
Once the Preliminary Detailer has created the Design Layout Sheet and added the borings and details of the proposed bridge to the plat and profile sheets, they should be checked by the Preliminary Designer.  These sheets are the end product of the Preliminary Design process and will be used to perform the structural calculations for the Final Design phase of the bridge, which results in the production of the contract plans.  Here is a list of items to include.
 
Once the Preliminary Detailer has created the Design Layout Sheet and added the borings and details of the proposed bridge to the plat and profile sheets, they should be checked by the Preliminary Designer.  These sheets are the end product of the Preliminary Design process and will be used to perform the structural calculations for the Final Design phase of the bridge, which results in the production of the contract plans.  Here is a list of items to include.
Line 681: Line 905:
 
|1.)||colspan="2"|General Information
 
|1.)||colspan="2"|General Information
 
|-
 
|-
|&nbsp;||a.||Live load designation
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|&nbsp;||a.||Route and structure classifications
 
|-
 
|-
|&nbsp;||b.||Traffic counts for the design year (ADT and ADTT).
+
|&nbsp;||b.||Live load designation
 
|-
 
|-
|&nbsp;||c.||Tie station (if applicable).
+
|&nbsp;||c.||Traffic counts for the design year (AADT and AADTT).
 
|-
 
|-
|&nbsp;||d.||Beginning station.
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|&nbsp;||d.||Tie station (if applicable).
 
|-
 
|-
|&nbsp;||e.||Horizontal curve data.
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|&nbsp;||e.||Beginning station.
 
|-
 
|-
|&nbsp;||f.||Profile grade information (including offset from CL of roadway or median).
+
|&nbsp;||f.||Horizontal curve data.
 
|-
 
|-
|&nbsp;||g.||Excavation datum.
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|&nbsp;||g.||Profile grade information (including offset from CL of roadway or median).
 +
|-
 +
|&nbsp;||h.||Excavation datum.
 
|-
 
|-
 
|2.)||colspan="2"|Superstructure
 
|2.)||colspan="2"|Superstructure
Line 699: Line 925:
 
|&nbsp;||a.||Type and span lengths.
 
|&nbsp;||a.||Type and span lengths.
 
|-
 
|-
|&nbsp;||b.||Roadway widths and type of barrier curbs.
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|&nbsp;||b.||Roadway widths and type of barrier or railing.
 
|-
 
|-
 
|3.)||colspan="2"|Substructure
 
|3.)||colspan="2"|Substructure
Line 707: Line 933:
 
|&nbsp;||b.||Types of all bents.
 
|&nbsp;||b.||Types of all bents.
 
|-
 
|-
|&nbsp;||c.||Locations of cross-bracing or webs.
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|&nbsp;||c.||Type and locations of sway bracing for concrete pile cap intermediate bent with HP pile.
 
|-
 
|-
 
|&nbsp;||d.||Locations and top of wall elevations for collision walls.
 
|&nbsp;||d.||Locations and top of wall elevations for collision walls.
 +
|-
 +
|&nbsp;||e.||Embedment of encasement for encased pile cap bent.
 +
|-
 +
|&nbsp;||f.||Location of tie beam.
 +
|-
 +
|&nbsp;||g.||Bottom elevations of web beam.
 
|-
 
|-
 
|4.)||colspan="2"|End Bents (Abutments)
 
|4.)||colspan="2"|End Bents (Abutments)
Line 717: Line 949:
 
|&nbsp;||b.||Berm elevations.
 
|&nbsp;||b.||Berm elevations.
 
|-
 
|-
|&nbsp;||c.||Type and extent of slope protection and need for geotextile material.
+
|&nbsp;||c.||Type and extent of spill and side slope protection (permanent erosion control geotextile fabric is required).
 
|-
 
|-
|&nbsp;||d.||Angle of internal friction to be used for deadman anchors.
+
|&nbsp;||d.||Bridge end drainage provisions per district (drain basins<sup>'''1'''</sup>, rock blanket, drain flumes) (Rdwy. Item)
 +
|-
 +
|&nbsp;||e.||Angle of internal friction to be used for deadman anchors.
 
|-
 
|-
 
|5.)||colspan="2"|Foundations
 
|5.)||colspan="2"|Foundations
Line 725: Line 959:
 
|&nbsp;||a.||Type and lengths of all piling.
 
|&nbsp;||a.||Type and lengths of all piling.
 
|-
 
|-
|&nbsp;||b.||Minimum tip elevations for all piles.
+
|&nbsp;||b.||Minimum galvanized penetration  (elevation)
 
|-
 
|-
|&nbsp;||c.||Location and elevation for any preboring.
+
|&nbsp;||c.||Minimum tip elevations for all piles.
 
|-
 
|-
|&nbsp;||d.||Location of any pile point reinforcement (shoes).
+
|&nbsp;||d.||Location and elevation for any preboring.
 
|-
 
|-
|&nbsp;||e.||Types of footings, their elevations and allowable bearing (if applicable).
+
|&nbsp;||e.||Pile point reinforcement (shoes) required for all structural steel HP piles. When Geotechnical Section indicates pile point reinforcement needed and show pile point type on boring log for CIP pile, then recommended pile point reinforcement type shall be shown on Design Layout.  
 
|-
 
|-
|&nbsp;||f.||Location of any cofferdams and/or seal courses.
+
|&nbsp;||f.||Types of footings, their elevations and allowable bearing (if applicable).
 
|-
 
|-
|&nbsp;||g.||End bearing and side bearing capacity for any drilled shafts.
+
|&nbsp;||g.||Location of any cofferdams and/or seal courses.
 
|-
 
|-
|&nbsp;||h.||Top of Rock Socket elevations and their minimum lengths.
+
|&nbsp;||h.||End bearing and side bearing capacity for any drilled shafts.
 +
|-
 +
|&nbsp;||i.||Top of Rock Socket elevations and their minimum lengths.
 +
|-
 +
|&nbsp;||j.||Estimated Maximum Scour Depth (Elev.)<sup>'''2'''</sup>
 +
|-
 +
|&nbsp;||k.||Minimum pile cleanout penetration (Elev.)<sup>'''3'''</sup>
 
|-
 
|-
 
|6.)||colspan="2"|Traffic Handling
 
|6.)||colspan="2"|Traffic Handling
Line 765: Line 1,005:
 
|&nbsp;||f.||Overtopping frequency and discharge if less than 500 yr.
 
|&nbsp;||f.||Overtopping frequency and discharge if less than 500 yr.
 
|-
 
|-
|9.)||colspan="2"|Miscellaneous
+
|9.)||colspan="2" |Seismic Information (New Bridge or Wall) (Applies to both dynamic and static designs)
 +
|-
 +
|&nbsp;||a.|| Site Class, Seismic Design Category, A<sub>s</sub>, S<sub>D1</sub>
 +
|-
 +
|&nbsp;||b.|| Either “LRFD Seismic Details Only” or “LRFD Complete Seismic Analysis”
 +
|-
 +
|&nbsp;||c.<br/><br/>|| For Nonseismic (or static) designs, Seismic Design Category A, A<sub>s</sub>, S<sub>D1</sub> (All new designs must meet SDC A. See [[#751.1.2.13 Earthquake (Seismic) Consideration|EPG 751.1.2.13 Earthquake (Seismic) Consideration]].)
 +
|-
 +
|10.)||colspan="2"|Miscellaneous
 
|-
 
|-
 
|&nbsp;||a.||Locations of Bridge Approach Slabs.
 
|&nbsp;||a.||Locations of Bridge Approach Slabs.
Line 779: Line 1,027:
 
|&nbsp;||f.||Use of weathering steel or color of paint (steel girders).
 
|&nbsp;||f.||Use of weathering steel or color of paint (steel girders).
 
|-
 
|-
|&nbsp;||g.||Name and phone number of District Contact.
+
|&nbsp;||g.||Name and phone number of district contact.
 
|-
 
|-
|&nbsp;||h.||Preliminary cost estimate.
+
|&nbsp;||h.||Preliminary Cost Estimate.
 
|-
 
|-
 
|&nbsp;||i.||Details of any utilities to be attached to the bridge.
 
|&nbsp;||i.||Details of any utilities to be attached to the bridge.
Line 793: Line 1,041:
 
|&nbsp;||m.||Location of Maint. facility contractor is to use for delivery of MoDOT retained items.
 
|&nbsp;||m.||Location of Maint. facility contractor is to use for delivery of MoDOT retained items.
 
|-
 
|-
|&nbsp;||n.||Directory/path for any Ceal, Geopak or Microstation files used for layout of bridge.
+
|&nbsp;||n.||Directory/path for any Ceal, Geopak or MicroStation files used for layout of bridge.
 +
|}
 +
{| style="margin: 1em auto 1em auto"
 +
|-
 +
|width="20"|&nbsp;||colspan="2" align="left"|'''1''' Drain basins can be included with concrete approach pavement per district. (Rdwy. Item)
 +
|-
 +
|&nbsp;||colspan="2" align="left"|'''2''' Show maximum of total scour depths estimated for multiple return periods in years from Preliminary design which should be
 +
|-
 +
||&nbsp;||width="10"|&nbsp;||given on the Design Layout. Show the controlling return period (e.g. 100, 200, 500) in Foundation Data. If return periods are different for different bents, add a new line in Foundation Data.<br/>On the plans report note EPG 751.50 E2.22 for CIP pile.
 +
|-
 +
|&nbsp;||colspan="2" align="left"|'''3''' Show for open ended CIP piles.
 
|}
 
|}
 +
  
 
Once the Preliminary Detailer and Designer are in agreement on these items, the entire layout folder should be submitted to the SPM for their review.  The SPM will then request a Design Layout Conference with the Assistant State Bridge Engineer and the Structural Resource Manager.
 
Once the Preliminary Detailer and Designer are in agreement on these items, the entire layout folder should be submitted to the SPM for their review.  The SPM will then request a Design Layout Conference with the Assistant State Bridge Engineer and the Structural Resource Manager.
Line 805: Line 1,064:
 
*Enter the Date to Final Design in the Bridge Survey Book and the Survey Rcv. Database
 
*Enter the Date to Final Design in the Bridge Survey Book and the Survey Rcv. Database
 
*Supply a copy of the Design Layout Sheet to Development and Review.
 
*Supply a copy of the Design Layout Sheet to Development and Review.
*Copy all of the Microstation files in house to
+
*Copy all of the MicroStation files in house to
 
*pwname:\\MoDOT\Documents\Central Office\Bridge\A_Prelim_design\district\job no.
 
*pwname:\\MoDOT\Documents\Central Office\Bridge\A_Prelim_design\district\job no.
 
*(Consultants contact Structural Liaison Engineer).
 
*(Consultants contact Structural Liaison Engineer).
  
The SPM should then enter the following information into Bloodhound.
+
The SPM should then enter the following information into Bloodhound:
 
*Span layout information
 
*Span layout information
 
*Preliminary Cost Estimate
 
*Preliminary Cost Estimate
Line 819: Line 1,078:
 
The SPM will then send a request for a Final Designer to the Structural Resource Manager.
 
The SPM will then send a request for a Final Designer to the Structural Resource Manager.
  
===751.1.2.31 FHWA Submittal===
+
===751.1.2.32 FHWA Submittal===
  
Full FHWA oversight is required for the following projects:
+
Federal involvement is determined in accordance with [[:Category:123 Federal-Aid Highway Program#123.1.1 FHWA Oversight - National Highway System|EPG 123.1.1 FHWA Oversight – National Highway System]].  Projects which are delegated for federal involvement for preliminary design on the PODI matrix must be submitted to FHWA for approval.
  
*Interstate projects equal to or exceeding $1 million in estimated costs
+
The submittal should include the following:
*[[:Category:910 Intelligent Transportation Systems|Intelligent Transportation System (ITS)]] projects
 
*Major bridge projects (over 1,000 feet long or span over 400 feet) or unique designs, operational features, unusual geotechnical or hydraulic features on the National Highway System (NHS).  If the project is located off of the interstate and not sufficiently complex to warrant FHWA involvement (i.e. The project is primarily for applying a latex modified wearing surface), then FHWA oversight is not required.
 
 
 
 
 
For FHWA oversight, the layout needs to be submitted to FHWA for their approval.  The submittal should include the following:
 
  
 
*[[Media:Layout to FHWA.doc|Cover letter]]
 
*[[Media:Layout to FHWA.doc|Cover letter]]
 
*One set of half-sized plat and profile sheets
 
*One set of half-sized plat and profile sheets
 
*One copy of Design Layout Sheet
 
*One copy of Design Layout Sheet
*One copy of completed form BR105R (gray sheet)
+
*One copy of completed Bridge Survey Report
 
*One copy of the Borings report including Cover Letter from Materials
 
*One copy of the Borings report including Cover Letter from Materials
*One copy of each approved [[131.4 Design Exception Process|Design Exception]] (if applicable)
+
*One copy of each approved [[131.1 Design Exception Process|Design Exception]] (if applicable)
 
*One copy of the Bridge Deck Condition Survey Summary (if applicable)
 
*One copy of the Bridge Deck Condition Survey Summary (if applicable)
 
*One copy of the Bridge Rehab Checklist (if applicable)
 
*One copy of the Bridge Rehab Checklist (if applicable)
Line 845: Line 1,099:
 
That is the end of the Preliminary Design phase of bridge design at MoDOT.
 
That is the end of the Preliminary Design phase of bridge design at MoDOT.
  
===751.1.2.32 Aesthetic Enhancements===
+
===751.1.2.33 Aesthetic Enhancements===
  
 
Aesthetic enhancements can include everything from form liners and different colored paints to actual brick or stonework on the bridge.  The district is required to inform the Bridge Division if aesthetic enhancements will be required on a bridge.  Aesthetic enhancements should be discussed by the core team during the scoping process.
 
Aesthetic enhancements can include everything from form liners and different colored paints to actual brick or stonework on the bridge.  The district is required to inform the Bridge Division if aesthetic enhancements will be required on a bridge.  Aesthetic enhancements should be discussed by the core team during the scoping process.
Line 851: Line 1,105:
 
Note: Galvanized slab drains are to remain unpainted unless otherwise requested by the district.  The required special provision is available if the district wishes to paint the galvanized slab drains.
 
Note: Galvanized slab drains are to remain unpainted unless otherwise requested by the district.  The required special provision is available if the district wishes to paint the galvanized slab drains.
  
==751.1.3 Overlays/Rehabs/Redecks/Widenings==
+
'''Specifying Form Liners'''
 +
 
 +
Form liners are typically supplied in 4 ft. wide sections. Consideration should be given to specifying concrete work in 2 ft. increments to avoid waste of form liner. Use of 1 ft. increments may be possible. Avoid specifying work requiring less than 1 ft. increments of form liner without approval of the Structural Project Manager or Structural Liaison Engineer. Specifying work requiring form liner using other than 4 ft. increments may affect cost and should be reviewed.
 +
 
 +
===751.1.2.34 Blast Loading Considerations===
 +
 
 +
Consideration should be given to the blast loading provisions given in ''AASHTO LRFD Bridge Design Specifications'' and ''AASHTO Bridge Security Guidelines'' for major bridges only and with the approval of the State Bridge Engineer.
 +
 
 +
Requirements for provision of blast loading protection and for structural design should be documented on the Bridge Memorandum and Design Layout.
 +
 
 +
All documentation associated with consideration of and requirements for blast loading protection and/or structural design including structural design computations should be detached or separated from other publicly available documents and marked “Not for Public Consumption.”
 +
 
 +
===751.1.2.35 Bridge Approach Slabs===
 +
 
 +
See [[:Category:503 Bridge Approach Slabs|EPG 503 Bridge Approach Slabs]].
 +
 
 +
===751.1.2.36 Bridge End Drainage===
 +
 
 +
See [[:Category:503 Bridge Approach Slabs|EPG 503 Bridge Approach Slabs]].
 +
 
 +
==751.1.3 Wearing Surfaces/Rehabs/Redecks/Widenings==
 
===751.1.3.1 Overview===
 
===751.1.3.1 Overview===
  
Modifying existing bridges is quite different than laying out new bridges. These types of projects can be broken into four general categories:
+
Modifying existing bridges is quite different from laying out new bridges. Bridge wearing surfaces (overlays), rehabs, redecks and only widenings when the substructure is not being widened require the preparation and approval of a Bridge Memo as the only official written document requiring signatory approval (see [[#751.1.2.19 Bridge Memorandums|EPG 751.1.2.19 Bridge Memorandums]]) as a matter of procedure. A Design Layout is not required in these instances. However, bridge widenings when substructure and foundation work are required will require procedurally both a Bridge Memo and a Design Layout for signatory approval since soundings for exploring subsurface conditions will be required for the foundations.
 +
 
 +
These types of projects can be broken into four general categories:
  
#Overlaying an existing bridge as part of a roadway overlay project.
+
#Adding a wearing surface to an existing bridge as part of a roadway overlay project.
 
#Rehabilitating and/or redecking an existing bridge as a stand alone programmed project.
 
#Rehabilitating and/or redecking an existing bridge as a stand alone programmed project.
 
#Widening an existing bridge to meet minimum shoulder width requirements as part of a roadway overlay project.
 
#Widening an existing bridge to meet minimum shoulder width requirements as part of a roadway overlay project.
 
#Widening an existing bridge to add lanes as part of a roadway project.
 
#Widening an existing bridge to add lanes as part of a roadway project.
  
===751.1.3.2 Bridges on Resurfacing Projects===
+
===751.1.3.2 Documentation===
  
This is probably the most common type of project. The first step is to determine the limits of the project. This can be done by looking at the description and log miles of the project in the Program Book. The District Contact should also be consulted to make sure the project limits have not changed.  The second step is using the Bridge Maps produced by the Maintenance Division to locate any and all bridges within the limits of the project.
+
A [[media:751.1.3.2_Structural_Rehabilitation_Checklist.xlsm|structural rehabilitation checklist]] shall be required for determining the current condition and documenting all needed improvements regardless of budget restraints. It is critical to control future growth in project scope or cost overruns during construction that is checklist captures all needed repairs using accurate quantities corresponding to contract bid items. Staff responsible for filling out checklist should contact the Bridge Division if assistance is needing in correlating deterioration with appropriate contract bid items.
  
 +
A deck test is not required but may be useful in determining the most appropriate wearing surface for bridges with deck ratings of 5 or 6.
  
Once the Bridge Nos. for these structures are known, obtain a copy of the Bridge Maintenance report for each structure.  These reports contain the log mile for each structure.  Compare this to the log mile limits of the project.  If the log mile on the report indicates the bridge is outside of the project limits, check with the District Contact again to see if the bridge is to be included in the project.
+
A pull off test is not required but may be useful in determining the viability of polymer wearing surface.
  
 +
Both deck tests and pull off tests are performed by the Preliminary and Review Section.
  
If a bridge falls within the project limits, it must be evaluated to see if it meets the current safety criteria for such items as shoulder width and curb type/height.  If the job will be built with federal funds, any substandard safety item must be remedied or handled with a [[131.4 Design Exception Process|design exception]].  If the job will be built with 100% state funds, the bridge can be left alone (no safety improvements).
+
A [[#751.1.2.18 Bridge Memorandums|Bridge Memorandum]] shall be required for documenting proposed construction work and estimated construction costs for district concurrence.  
  
===751.1.3.3 Curb Type and Height===
+
A [[#751.1.2.31 Finishing Up Design Layout|Design Layout]] shall be required only for widening projects where there is proposed foundation construction.
  
Three types of curbs are acceptable in Missouri;  Thrie Beams, Safety Barrier Curbs (SBC) and Curb and Parapets.
+
===751.1.3.3 Bridges on Resurfacing Projects===
  
When using the SBC or Curb and Parapet, a five-hole bolt pattern must be used to connect the approach railing to the bridge curb.
+
This is probably the most common type of project.  The first step is to determine the limits of the project.  This can be done by looking at the description and log miles of the project in the Program Book.  The district contact should also be consulted to make sure the project limits have not changed.  The second step is using the Bridge Maps produced by the Maintenance Division to locate any and all bridges within the limits of the project.
  
 +
Once the Bridge Nos. for these structures are known, obtain a copy of the Bridge Maintenance report for each structure.  These reports contain the log mile for each structure.  Compare this to the log mile limits of the project.  If the log mile on the report indicates the bridge is outside of the project limits, check with the district contact again to see if the bridge is to be included in the project.
  
{|border="0"
+
If a bridge falls within the project limits, it must be evaluated to see if it meets the current safety criteria for such items as shoulder width and curb type/height.  If the job will be built with federal funds, any substandard safety item must be remedied or handled with a [[131.1 Design Exception Process|design exception]].  If the job will be built with 100% state funds, the bridge can be left alone (no safety improvements).
 +
 
 +
===751.1.3.4 Barrier or Railing Type, Height and Guidelines for Curb Blockouts===
 +
 
 +
AASHTO LRFD uses the term “railing” to refer to all types of bridge traffic barrier systems used on bridges. MoDOT uses the term “barrier” for solid concrete bridge railing (single-faced on the edge of roadway and dual-faced medians) and the term “railing” for barrier systems consisting of a rail(s) and supports. Several types of barrier and railing are acceptable for use on bridges in Missouri (see [[#Common Bridge Barrier and Railing (for Rehabilitations)|Common Bridge Barrier and Railing]]); thrie beam railing, Type A, B, C, D, G and H barrier; curb and parapet barrier, two tube rail; or FHWA MASH or NCHRP 350 approved crash tested barrier or railing meeting TL-4 rating as given on the [https://safety.fhwa.dot.gov/roadway_dept/countermeasures/reduce_crash_severity/listing.cfm?code=long FHWA Bridge Railings website].
 +
 
 +
While meeting MASH TL-4 requirements is preferred, existing barrier or railing may be used in place if meeting NCHRP 350 TL-3 or TL-4 requirements, or existing barrier or railing may be retrofitted to meet same requirements. See [[#Common Bridge Barrier and Railing (for Rehabilitations)|Common Bridge Barrier and Railing (for Rehabilitations)]] for further guidance.
 +
 
 +
New bridge barrier or railing on existing bridges shall meet MASH TL-4 requirements on major routes with design speeds greater than 45 mph. Similarly, MASH TL-4 barrier or railing is required on minor and low volume routes with design speeds greater than 55 mph or AADT ≥ 1700. New bridge barrier or railing on existing bridges for all other major, minor, and low volume routes may instead meet MASH TL-3, NCHRP 350 TL-4 or NCHRP 350 TL-3 requirements where circumstances restrict the use of a MASH TL-4 barrier or railing. In any case, the new barrier or railing shall not be rated lower than the existing barrier or railing. The hierarchy for crash test ratings in descending order is listed below with qualified barriers and railings in Missouri:
 +
 +
:* MASH (2016) TL-4 (Type C and D barrier)
 +
:* MASH TL-3 (Type H barrier, Type A and B barrier)
 +
:* NCHRP 350 TL-4 (two tube railing, 12” x 29” vertical barrier)
 +
:* NCHRP 350 TL-3 (thrie beam railing).
 +
 
 +
Type C and D barrier shall be used on all redecks, rehabs and widenings where the full length of barrier is being replaced with exceptions for the following:
 +
:* sight distance concerns. Type H barrier or two tube rail is recommended.
 +
:* rating concerns where the weight of the barrier prohibits its use or causes impractical restrictions or costs for the project. Type H barrier or two tube rail is recommended.
 +
:* roadway width restrictions. Two tube rail or thrie beam rail is recommended.
  
|A)||colspan="2"|Thrie Beam
+
The approach railing does not need to match the test level of the bridge barrier or railing.  MoDOT standard approach rails typically do not rate higher than TL-3.
|-
 
|&nbsp;||valign="top"|i)||If the deck is less than 8.5” thick, the attachment must bolt through the deck with a plate on the bottom side of the deck.  The details showing anchoring with a bent stud formed within the deck is no longer acceptable.  (The deck is too thin and the deck edge breaks off during a collision.)
 
|-
 
|&nbsp;||valign="top"|ii)||The center of the rail shall be 21” to the top of the finished driving surface.
 
|-
 
|&nbsp;||valign="top"|iii)||Thrie Beams are not a preferred railing for interstate or high ADT’s.
 
|-
 
|&nbsp;
 
|-
 
|B)||colspan="2"|Safety Barrier Curb (SBC)
 
|-
 
|&nbsp;||valign="top"|i)||If installed at the time of the driving surface, the top of the curb should be no less tha 2’-8” above the driving surface.
 
|-
 
|&nbsp;||valign="top"|ii)||If the wearing surface is installed after the SBC is in place, the wearing surface shall be no greater than 2”, making the curb 2’-6”.
 
|-
 
|&nbsp;
 
|-
 
|C)||colspan="2"|Curb and Parapet
 
|-
 
|&nbsp;||valign="top"|i)||The concrete portions of the curb and parapet are the only components that are used in calculating the height of the railThe handrails are not crash worthy.
 
|-
 
|&nbsp;||valign="top"|ii)||Curb and Parapets can be as short as 2’-3” from the driving surface if no raise in grade is added.  Once a wearing surface, (other than ¼” epoxy), is applied, the parapet must then be heightened to 2’-8” above the finished driving surface.  This is generally done by adding curb blockouts to the existing curb and parapet.
 
|-
 
|&nbsp;||valign="top"|iii)||The horizontal dimension of the step from the driving face of the curb to the driving face of the parapet is recommended to be between 0” to 3” but cannot to exceed 6”.  If a curb blockout is used, this dimension cannot exceed 3”.
 
|-
 
|&nbsp;||valign="top"|iv)||Many times the end posts are not the same width as the parapets.  Check to see if the end posts are  wider and if they extend towards the driving lanes or to the outside edge.  It may be necessary to remove the end posts all together to accommodate for blockouts.
 
|}
 
  
 +
When using a concrete barrier, a five-hole bolt pattern shall be used for connecting the approach railing to the bridge barrier.
  
<center>[[Image:751.1_Prelim_Design_Blockout_on_Exist_Curb_No._1.gif]]</center>
+
Bridge barrier or railing on single lane bridges may be used in place if for no other reason than the grade is not being raised. Thin wearing surfaces measuring no more than 3/8 inch will not be considered as raising the grade.
  
<center>'''BLOCKOUT ON TOP OF EXISTING CURB'''</center>
+
'''Thrie Beam Railing (Bridge Guardrail)'''
  
 +
If the deck is less than 8½ inches thick, the attachment must bolt through the deck with a plate on the bottom side of the deck. In the past, MoDOT used details where a bent stud was formed within the deck. This is no longer acceptable because of observed failure in thin decks where the edge can break off and the bottom of slab can pop out during a collision.
  
<center>[[Image:751.1_Prelim_Design_Blockout_on_Exist_Curb_No._2.gif]]</center>
+
The center of the thrie beam shall be a minimum of 21 inches to the top of the finished driving surface.  
  
<center>'''BLOCKOUT ON TOP OF EXISTING CURB'''</center>
+
Thrie beam railing shall not be installed on new or replacement bridges or widenings. Thrie beam shall not be used for grade crossings or other areas where drainage over the side of the deck is a concern.
 +
 
 +
'''Type A, B, C, D, G and H Barriers '''
  
 +
If installed at the same time as the driving surface, the top of the barrier shall not be less than 32 inches above the driving surface.
  
<center>[[Image:751.1_Prelim_Design_Blockout_on_Exist_Curb_No._3.gif]]</center>
+
If a wearing surface is installed after the barrier is in place, the wearing surface thickness shall not be made greater than that whereby the barrier height is made less than 30 inches , i.e. the final grade with wearing surface installed shall not increase more than 2 inches.
 +
<div id="3. If an existing wearing surface"></div>
 +
If an existing wearing surface is replaced next to Type A or B barrier, the new wearing surface thickness shall not be made less than that where by the height above the driving surface of the break between the upper and lower slope of the barrier is made greater than 13 inches.
 +
 
 +
'''Curb and Parapet Barrier'''
  
<center>'''BLOCKOUT ON TOP OF EXISTING CURB'''</center>
+
The concrete portions of the curb and parapet are the only components used in determining the height of the barrier for establishing if the system meets current standards or is substandard. The handrails are not crashworthy and therefore are not considered as part of the height of the barrier.
 +
 +
Curb and parapet were typically constructed 27 inches measured from the driving surface to top of parapet.
  
 +
Sections of curb and parapet may be replaced without consideration of upgrading.
  
<center>[[Image:751.1_Prelim_Design_Blockout_on_Exist_Curb_No._4.gif]]</center>
+
When a wearing surface is to be applied, the height of the existing curb and parapet system shall be determined from the existing driving surface and if necessary shall be heightened to 32 inches or 36 inches above the proposed driving surface based on Guidelines for Curb Blockout, immediately below. Increasing the height of an existing curb and parapet is generally done by adding a blockout to the curb and parapet (i.e., curb blockout).
  
<center>'''BLOCKOUT ON TOP OF EXISTING CURB'''</center>
+
====Guidelines for Curb Blockout====
  
 +
<u>Background and Application</u>
  
 +
Guidelines were developed considering Practical Design concepts (refer to [[:Category:143 Practical Design|EPG 143 Practical Design]]).
  
<center>'''ACCEPTABLE CURB BLOCKOUT CONFIGURATIONS'''</center>
+
Guidelines apply to bridges to be resurfaced and/or rehabilitated that have concrete curb and parapet barrier.  They do not apply to bridges on Contract Leveling Course projects that are in accordance with [[:Category:402 Bituminous Surface Leveling#402.1 Design of Contract Leveling Course Projects|EPG 402.1 Design of Leveling Course Projects]].
  
 +
When resurfacing and rehabilitating a bridge, consideration shall be given to upgrading the curb and parapet barrier by increasing the overall height if the barrier does not meet criteria given in these guidelines.  The guidelines are based upon reviewing conditions that require satisfying height and horizontal parapet offset requirements using the minimum height of 27 inches in accordance with 2002 AASHTO 17<sup>th</sup> Edition and earlier editions and a maximum horizontal parapet offset of 6 inches from curb face to parapet face which is a MoDOT requirement ([[:Category:128 Conceptual Studies|EPG 128 Conceptual Studies]], 3R-Rural Design Criteria recommends a 6-inch brush curb).  Upgrades to curb and parapet should be made by constructing a curb blockout.  The following guidelines describe circumstances where it is, or is not, necessary to upgrade curb and parapet that were either originally built substandard or made substandard due to an earlier wearing surface or will be made substandard due to a proposed wearing surface.
  
&nbsp;
+
<u>Guidelines</u>
&nbsp;
 
  
 +
Look at the 5-year history of accidents on the bridge (beginning log mile to ending log mile). 
  
<center>[[Image:751.1_Prelim_Design_Holes_for_New_BR_Anchor_Attachment_Part_Elev_No_1.gif]]</center>
+
If there were any accidents in this time period that involved a vehicle ''striking the curb'', then curb and parapet not meeting current standards should be upgraded to meet the current (2016)MASH TL-4 requirement which is to increase the height to 36 inches. A 32” blockout height will be allowed, upon approval of the SPM or SLE, when either sight distance or weight restrictions are a concern.
  
<center>'''PART ELEVATION'''</center>
+
If there were NOT any accidents in the 5-year history AND if the grade is not being raised then it shall not be necessary to upgrade the curb and parapet.
{|border="0" align="center"
 
  
|valign="top"|Note:||width="300pt" |Existing holes (For guard rail attachment) in existing bridge parapet shall be filled with an approved epoxy mortar.
+
If the accident history or grade criteria are not met, then it shall be necessary to upgrade the curb and parapet. The district may submit a design exception to eliminate a curb blockout for bridges not on major routes and with AADT < 1700 when there is no history of accidents on the bridge and the grade is being raised no more than 2 inches from the 27-inch minimum height requirement.  
|}
 
  
 +
<u>Limiting Wearing Surface Thickness To Meet Guidelines</u>
  
<center>[[Image:751.1_Prelim_Design_Holes_for_New_BR_Anchor_Attachment_Elev_AA_No._1.gif]]</center>
+
The wearing surface thickness can be limited to that which would not cause the curb and parapet height to become substandard. An exception to this is a 1/4 to 3/8-inch height tolerance to allow for the possibility of placing a thin wearing surface on a bridge with an existing standard 27-inch high curb and parapet as measured from the original driving surface to the top of the parapet. Adding a thin wearing surface will not by itself make a satisfactory curb and parapet railing height substandard as reviewed and approved by MoDOT and FHWA. For overlay projects, where a curb blockout is already in place, the final blockout height shall not be less than 30 inches.
  
<center>'''ELEVATION A-A'''</center>
+
Note: In all cases, the allowable wearing surface thickness would also be dependent on a structural review to confirm that the weight of the wearing surface would not lead to overstresses or an unacceptable posting.
  
 +
<u>Details</u>
  
 +
The horizontal offset (or ledge) from the curb face to the parapet face is recommended to be between zero and 3 inches but shall not exceed 6 inches. If a curb blockout is used, the ledge shall not exceed 3 inches.
 +
 +
End posts are not always the same width as the parapets. If the end posts are wider and if they extend towards the driving lanes, it shall be necessary to remove the end posts completely in order to construct the curb blockouts. If end posts extend towards the outside of the bridge, it may not be necessary to remove the end posts.
  
<center>[[Image:751.1_Prelim_Design_Holes_for_New_BR_Anchor_Attachment_Part_Elev_No_2.gif]]</center>
+
The end treatment for the 36-inch blockout will require a maximum 6:1 slope to transition down to a maximum 32-inch end height near the guardrail attachment.  A 32-inch blockout does not require a reduced height for the end treatment.  The preferred end treatment will include a gradual width transition that approximates a 10:1 slope.  A block inset for the guardrail attachment should be avoided.
 +
[[image:751.1.3.4.jpg|center|700px]]
  
<center>'''PART ELEVATION'''</center>
 
{|border="0" align="center"
 
  
|valign="top"|Note:||width="300pt" |Existing holes (For guard rail attachment) in existing bridge parapet shall be filled with an approved epoxy mortar.
+
====Common Bridge Barrier and Railing (for Rehabilitations)====
 +
<center>
 +
{| border="1" class="wikitable" style="margin: 1em auto 1em auto" style="text-align:center"
 +
|+
 +
! style="background:#BEBEBE" |Type!! style="background:#BEBEBE" |Section<br/>(Test Level) !! style="background:#BEBEBE" width="160"|Allowed Wearing Surface !! style="background:#BEBEBE" width="180" |Required Retrofit !! style="background:#BEBEBE" width="210"| Notes
 +
|-
 +
|width="200"|'''Curb and Parapet'''<br/>(Brush Curb ≤ 6”)<br/> [[image:751.1.3.3 less than 6 in..jpg|130px]] || [[image:751.1.3.4 less than 6 section.jpg|130px]]<br/>(N/A) || 3/8” Thin Wearing Surface|| Use in place with curb blockout for wearing surfaces greater than 3/8” from original deck surface|| (1)
 +
|-
 +
|'''Curb and Parapet'''<br/>( Brush Curb > 6”)<br/>[[image:751.1.3.3 more than 6 in..jpg|130px]] || [[image:751.1.3.4 more than 6 section.jpg|130px]]<br/>(N/A) || None without retrofit|| Use in place with curb blockout (preferred) or thrie beam railing.||(1)<br/>Horizontal step must be 6” or less to be UIP.
 +
|-
 +
|'''Brush Curb with Steel Rail'''<br/> [[image:751.1.3.3 street rail.jpg|130px]] || [[image:751.1.3.4 brush section.jpg|130px]]<br/>(N/A) || None without retrofit ||Use in place with added curb blockout (preferred) or thrie beam railing.||(1)<br/>A variety of steel railing systems were employed on brush curbs. None are acceptable without retrofit.
 +
|-
 +
|'''Thrie Beam'''<br/> [[image:751.1.3.4 thrie beam.jpg|120px]] || [[image:751.1.3.4 thrie beam section.jpg|130px]]<br/>(NCHRP 350 TL-3) || 21” (Min.) from centerline of thrie beam to top of wearing surface||Use in place if minimum height to centerline of thrie beam is acceptable.||(2) and (4)<br/>May be embedded or bolted thru.<br/>W6x15 blockout is included for all new construction.<br/>Non-blocked railing may be used-in-place when no approach guardrail is provided.
 +
|-
 +
|'''Type A Barrier'''<br/>(Photo not available) || [[image:751.1.3.4 Type A.jpg|130px]]<br/>(MASH TL-3)|| Up to 2”|| Use in place.|| (1)
 +
|-
 +
|'''Type B Barrier'''<br/> [[image:751.1.3.3 safety barrier.jpg|130px]] || [[image:751.1.3.4 type b section.jpg|130px]]<br/>(MASH TL-3) || Up to 2” || Use in place. || (1)
 +
|-
 +
|'''Type C Barrier'''<br/>(Photo not available) || [[image:751.1.3.4 Type C.jpg|130px]]<br/>(MASH 2016 TL-4) || Up to 6”|| Use in place.|| (3)<br>Wearing surfaces greater than 3” require a bridge rating analysis
 +
|-
 +
|'''Type D Barrier'''<br/>[[image:751.1.3.4 type d.jpg|130px]] || [[image:751.1.3.4 type d section.jpg|130px]]<br/>(MASH 2016 TL-4) || Up to 6”||Use in place.||(3)<br/>Wearing surfaces greater than 3” require a bridge rating analysis
 +
|-
 +
|'''Type G Barrier'''<br/>(Photo not available) || [[image:751.1.3.4 Type G.jpg|130px]]<br/>(MASH 2016 TL-3)|| Up to 2”|| Use in place.|| (3)<br/>Use if Type C is considered impractical.
 +
|-
 +
|'''Type H Barrier'''|| [[image:751.1.3.4 type h section.jpg|150px]] <br/>(MASH 2016 TL-3)|| Up to 2”||Use in place.||(3)<br/>Use if Type D is considered impractical.
 +
|-
 +
|'''Steel Two Tube Rail'''<br/> [[image:751.1.3.3 steel two tube.jpg|130px]] || [[image:751.1.3.4 steel 2 section.jpg|130px]]<br/>(NCHRP 350 TL-4) || Up to 2”|| Use in place.|| (3) and (4)<br/>A 42” two tube rail has been successfully crash tested for TL-4, but an end treatment has not been approved for use.
 +
|-
 +
|'''12” x 29” Vertical Barrier'''<br/> [[image:751.1.3.4 vertical.jpg|130px]]  || [[image:751.1.3.4 vertical section.jpg|130px]] <br/>(NCHRP 350 TL-4) || Up to 2” ||End of barrier modification for new guardrail attachment.|| (1)
 +
|-
 +
|colspan=5 align="left" width="750"|(1) Shall not be used for redecks, widenings, and railing or cantilever full length replacements.<br/>(2) Typically specified for redecks, and railing or cantilever full length replacements. Shall not be used for widenings.<br/>(3) Typically specified for redecks, widenings, and railing or cantilever full length replacements.<br/>(4) Shall not be used on major routes with design speeds greater than 45 mph or on minor and low volume routes with design speeds greater than 55 mph or AADT ≥ 1700. May be used for all other major, minor, and low volume routes.  
 
|}
 
|}
 +
</center>
  
 +
Aluminum handrail is not crashworthy and does not contribute to barrier height. Use only the concrete portion.
  
&nbsp;
+
Many other, less common, barrier and railing systems have been constructed. Most are not crashworthy for rural highway speeds. Generally, the replacement of the existing barrier or railing is the only means to upgrade.
&nbsp;
 
  
 +
For additional information on curb blockouts, see [[#Guidelines for Curb Blockout|Guidelines for Curb Blockouts]].
  
<center>[[Image:751.1_Prelim_Design_Holes_for_New_BR_Anchor_Attachment_Elev_AA_No._2.gif]]</center>
+
{| style="margin: 1em auto 1em auto"
 +
|-
 +
|[[image:751.1.3.3 curb and parapet.jpg|275px]]|| [[Image:751.1 Prelim Design Acceptable Rail No. 4.jpg|225px]]
 +
|}
 +
A curb blockout is utilized along full length of the curb.  Bridge Division provides plans for curb blockouts.
  
{|border="0" align="center"
+
===751.1.3.5 Deck Repairs===
  
|valign="top"|*||width="300pt" |Remove this area of Safety Barrier Curb for Guard Rail Attachment
+
The project scope is developed from a thoroughly developed structural rehabilitation checklist which includes the typical repairs covered in [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 704].
|}
+
 
 +
'''Typical Repair'''
 +
 
 +
Cleaning and epoxy coating of the bottom and edges of the superstructure is preferred over slab edge repair and unformed superstructure repair because of the relative short life of these repair especially when over traffic. However, consult with Structural Project Manager or the Structural Liaison Engineer for urban regions where repairing the overhang may be preferred. If requested by the core team for aesthetics with extensive patchwork of repairs visible to public, specify on the Bridge Memorandum to apply tinted sealer to slab edge repair and unformed superstructure repair to blend repair to existing concrete.
 +
 
 +
'''Non-Typical Repair'''
  
 +
Modified deck repair is specified instead of half-sole deck repair on existing poor bridge decks to obtain a little more service life until it is practical to replace the bridge deck, superstructure or entire bridge.
  
<center>'''PART ELEVATION A-A'''</center>
+
On rare occasions shallow deck repair is used in combination with half-sole deck repair as a cost savings measure on major bridges. Consult with the structural project manager or the structural liaison engineer prior to specifying shallow deck repair.
  
 +
===751.1.3.6 Deck Treatment===
  
 +
The [[media:751.1.3.6 Bridge Wearing Surface Flowchart.pdf|Bridge Wearing Surface Flowchart]] has been developed to aid in the selection of the appropriate deck treatment.
  
<center>'''HOLES FOR NEW BRIDGE ANCHOR<br/>ATTACHMENT TO EXISTING CURB AND PARAPET'''</center>
+
When possible, multiple types of wearing surfaces should be allowed by specifying on the Bridge Memorandum the appropriate optional wearing surface. It shall also be specified if any of the wearing surfaces of the optional wearing surfaces are not allowed. The specific wearing surface shall be specified on the Bridge Memorandum when only one wearing surface option is allowed.
  
 +
'''Concrete Crack Filler'''
  
&nbsp;
+
Concrete crack filler in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 704] is typically used for bridges with deck ratings of 7, 8 or 9 with cracks 1/128 inch or less. May also be an option for bridges with deck ratings of 7, 8 or 9 with cracks greater than 1/128 inch and the deck fails a required pull off test.
&nbsp;
 
&nbsp;
 
  
 +
'''Concrete Wearing Surface'''
  
{|border="0" align="center" style="text-align:center"
+
A concrete wearing surface in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 505] is the preferred deck treatment for bridges with deck ratings of 5 or 6 so long as the barrier height does not become substandard and the bridge remains not posted (or if already posted not be reduced).
  
|[[Image:751.1_Prelim_Design_Acceptable_Rail_No._1.gif]]
+
Typically, the wearing surface thickness that has the least impact on existing grade is specified on the Bridge Memorandum as the minimum required thickness. When this thickness equals the minimum allowable thickness, as shown below, consider adding 1/2 inch to the minimum required thickness specified on the Bridge Memorandum for hydro demolition projects to provide coverage over existing aggregate protruding into the new wearing surface. For bridges with special repair zones where two different minimum hydro demolitions depths are specified, then two corresponding minimum required thicknesses shall be specified on the Bridge Memorandum.
|[[Image:751.1_Prelim_Design_Acceptable_Rail_No._2.gif]]
+
<center>
 +
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
|-
 
|-
|&nbsp;||* 2" (Max. Overlay)
+
!style="background:#BEBEBE"|Wearing Surface Type!!style="background:#BEBEBE"|Allowable Thickness
 +
|-
 +
|Latex Modified||align="center"| 1¾″ to 3″
 
|-
 
|-
|16" SBC (2'-8")<br/>(New Curb)||16" SBC (2'-8")<br/>(Exist. With Overlay)
+
|Silica Fume||align="center"| 1¾″ to 3″
 
|-
 
|-
|&nbsp;
+
|Latex Modified Very Early Strength||align="center"| 1¾″ to 3″
 
|-
 
|-
|[[Image:751.1_Prelim_Design_Acceptable_Rail_No._3.gif]]
+
|CSA Cement Very Early Strength||align="center"| 1¾″ to 3″
|[[Image:751.1_Prelim_Design_Acceptable_Rail_No._4.gif]]
 
 
|-
 
|-
|Curb & Parapet<br/>(No Overlay)||Curb & Parapet<br/>(Change in Grade)
+
|Steel Fiber Reinforced||align="center"| 3″ to 4″
 
|-
 
|-
|&nbsp;
+
|Low Slump||align="center"| 2¼″ to 3″
 
|-
 
|-
|colspan="2"|[[Image:751.1_Prelim_Design_Acceptable_Rail_No._5.gif]]
+
|Polyester Polymer||align="center"| ¾″ to 3″
|-
+
|}
|colspan="2"|Thrie Beam<br/>(Change in Grade)
+
</center>
 +
For a deck without an existing wearing surface, scarification of the deck producing a very rough texture in accordance with Sec 216.20 is required to produce a bondable surface for the new concrete wearing surface. Typically, 1/2 inch of scarification is specified on the Bridge Memorandum. Scarification equipment may not engage the deck when less than 1/2 inch of scarification is specified.
 +
 
 +
For a deck with an existing wearing surface, removing the existing wearing surface plus an additional amount of existing deck in accordance with Sec 216.30 is required to produce a very rough bondable surface for the new concrete wearing surface. Typically, 1/2 inch of additional existing deck is specified on the Bridge Memorandum. Removal equipment may not remove the entire existing wearing surface when less than 1/2 inch of additional deck is specified.
 +
 
 +
When the estimated deck repair is more than 30 percent of the deck, one inch shall be specified for scarification or for the additional amount of existing deck with the removal of an existing wearing surface. Verify there will be a minimum of 1/2 inch of concrete above the top bars after scarification or after the removal of the existing wearing surface and if necessary, reduce one-inch depth accordingly.
 +
 
 +
Total surface hydro demolition in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 216.110] performed after scarification or after the removal of the existing wearing surface is preferred for the establishment of a highly rough and bondable surface. For typical bridges, a minimum 1/2 inch of hydro demolition is specified on the Bridge Memorandum. For bridges with special repair zones, typically a 1/4-inch minimum is specified inside special repair zones to avoid deeper penetration into newly repaired areas and a 1/2-inch minimum is specified outside the special repair zones.
 +
 
 +
Removal of existing deck repair in accordance with Sec 216.110 is required prior to hydro demolition. The estimated quantities for these removals shall include all previous conventional deck repairs, regardless of condition except that for bridges with special repair zones, the removal of all sound and unsound existing deck repairs inside special repair zones shall be included in the estimated quantities for half-sole repair.
 +
 
 +
'''Polymer Wearing Surface'''
 +
 
 +
A polymer wearing surface in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 623] may only be used if the deck passes a required pull off test.  Polymer is typically used for bridges with deck ratings of 7, 8 or 9 with cracks greater than 1/128 inch.The polymer may also be an option for bridges with deck ratings of 5 or 6 that have load rating issues.
 +
<center>
 +
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
|-
 
|-
|&nbsp;
+
!style="background:#BEBEBE"|Polymer Options
 +
|-
 +
|1/4″ Epoxy Polymer
 
|-
 
|-
|colspan="2"|'''ACCEPTABLE RAILS'''
+
|3/8″ MMA Polymer Slurry
 
|}
 
|}
 +
</center>
 +
If requested by the core team, a black beauty type aggregate shall be specified on the Bridge Memorandum for MMA polymer slurry wearing surface.
 +
 +
If requested by the core team, a high friction (HFST) aggregate shall be specified on the Bridge Memorandum for MMA polymer slurry wearing surface pending a safety benefit/cost ratio analysis performed by district traffic staff. See [https://spexternal.modot.mo.gov/sites/de/_layouts/15/WopiFrame.aspx?sourcedoc={E8696531-19D1-4E99-9458-41E7D7F615C3}&file=NJSP1513.docx&action=default Roadway non-standard special provision NJSP1513] to reference aggregate requirements and surface friction test.
 +
 +
If requested by the core team, preparation of reflective deck cracks shall be specified on the Bridge Memorandum if during the scoping process there is concern of primer loss with reflective deck crack size at the precast panel joints.
  
===751.1.3.4 [http://epg.modot.mo.gov/forms/DE-Bridge/Structural%20Rehabilitation%20Checklist.xlt Structural Rehabilitation Checklist]===
+
'''Asphalt Wearing Surface or Seal Coat'''
 +
 
 +
Asphalt wearing surfaces in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 403], ultrathin asphalt wearing surfaces in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 413] and seal coats in accordance with [https://www.modot.org/missouri-standard-specifications-highway-construction Sec 409] are typically used on existing poor bridge decks to obtain a little more service life until it is practical to replace the bridge deck, superstructure or entire bridge.
 +
 
 +
Grade B1 seal coat aggregate shall be used whenever a bridge deck is to receive an asphalt wearing surface.
 +
 
 +
Grade A1 seal coat aggregate shall be used whenever the seal coat is to be the final riding surface. Grade C seal coats are no longer used for bridge applications because of dust issues.
 +
 
 +
===751.1.3.7 Bridge Approach Slabs===
 +
 
 +
Follow guidance for new bridges and see [[:Category:503 Bridge Approach Slabs|EPG 503 Bridge Approach Slabs]].
 +
 
 +
===751.1.3.8 Bridge End Drainage===
 +
 
 +
Follow guidance for new bridges and see  [[:Category:503 Bridge Approach Slabs|EPG 503 Bridge Approach Slabs]].
 +
 
 +
===751.1.3.9 Environmental Considerations: Asbestos and Lead===
 +
 
 +
Check [[:Category:145 Transportation Management Systems (TMS)|TMS]]<sup>'''1'''</sup> to see if an asbestos and lead inspection has been performed for a structure and include the applicable note shown immediately below on the Bridge Memorandum under the Special Notes Section. The report in TMS will be located in the Images link under the Media tab for the structure. If there is not a report in TMS, contact the Assistant State Bridge Engineer for a report not yet uploaded to TMS. Include the applicable note of the two shown immediately below on the Bridge Memorandum depending on whether an inspection has not been performed or if the inspection report indicates that asbestos or lead, or both are present or not present. (These notes are also applicable for new replacement structures that involve removal of any part of an existing structure.)
 +
 
 +
:''“Asbestos and lead inspections have not been performed on this structure (Bridge/Culvert # XXXXX). The Bridge Division will request these inspections and will include the report in the electronic deliverables folder when submitting contract documents to the Design Division for the Letting (Bridge Item).
 +
 
 +
:''“Asbestos and lead inspections have been performed on this structure (Bridge/Culvert # XXXXX). Results indicate that <u>asbestos is present</u> <u>lead is present</u> <u>both are present</u> <u>both are not present</u>. The Bridge Division will include the inspection report in the electronic deliverables folder when submitting contract documents to the Design Division for the Letting (Bridge Item).”''
 +
 
 +
<sup>'''1'''</sup>Available only to MoDOT employees. All others: contact the Bridge Division or the Structural Liaison Engineer directly for information related to EPG 751.1.3.9 Environmental Considerations: Asbestos and Lead.
  
 
==751.1.4 Retaining Walls==
 
==751.1.4 Retaining Walls==
 
===751.1.4.1 Overview===
 
===751.1.4.1 Overview===
  
This section is intended to help with the issues unique to retaining walls.  Many sections in the "Bridges/Boxes" section of this manual will still need to be used when working on retaining walls.
+
This article is intended to help with the issues unique to retaining walls.  Many portions of [[751.1 Preliminary Design#751.1.2 Bridges/Boxes|EPG 751.1.2 Bridges/Boxes]] will still need to be used when working on retaining walls.
  
  
Line 1,033: Line 1,413:
 
There are two general types of retaining walls used by MoDOT; cast-in-place (CIP) concrete walls and mechanically stabilized earth (MSE) walls.  MSE walls are the preferred type due to their lower cost; however, there are several times when MSE walls cannot be used.  These include:
 
There are two general types of retaining walls used by MoDOT; cast-in-place (CIP) concrete walls and mechanically stabilized earth (MSE) walls.  MSE walls are the preferred type due to their lower cost; however, there are several times when MSE walls cannot be used.  These include:
  
*When barrier curb must be attached to the top of the wall.
+
*When barrier or railing must be attached to the top of the wall.
 
*When the underlying soil cannot support the weight of the fill and wall (must use CIP on piling).
 
*When the underlying soil cannot support the weight of the fill and wall (must use CIP on piling).
 
*When you don’t have adequate room behind the wall for the reinforcing straps.
 
*When you don’t have adequate room behind the wall for the reinforcing straps.
  
In general a minimum reinforcement length of 8.0 ft. regardless of wall height, has been recommended based on historical practice, primarily due to size limitations of conventional spreading and compaction equipment.  Shorter minimum reinforcement lengths, on the order of 6.0 ft. , but less than 70 percent of the wall height, can be considered if smaller compaction equipment is used, facing panel alignment can be maintained, and minimum requirements for wallexternal stability are met.
+
In general a minimum reinforcement length of 8.0 ft., regardless of wall height, has been recommended based on historical practice, primarily due to size limitations of conventional spreading and compaction equipment.  Shorter minimum reinforcement lengths, on the order of 6.0 ft., but no less than 70 percent of the wall height, can be considered if smaller compaction equipment is used, facing panel alignment can be maintained, and minimum requirements for wall external stability are met.
  
The requirement for uniform reinforcement length equal to 70 percent of the structure height has no theoretical justification, but has been the basis of many successful designs to-date.  Parametric studies considering minimum acceptable soil strengths have shown that structure dimensions satisfying all of the requirements of Article 11.10.5 require length to height ratios varing gfrom 0.8H for low satructures, i.e. 10.0 ft., to 0.63 H for high structures, i.e. 40.0 ft.
+
The requirement for uniform reinforcement length equal to 70 percent of the structure height has no theoretical justification, but has been the basis of many successful designs to-date.  Parametric studies considering minimum acceptable soil strengths have shown that structure dimensions satisfying all of the requirements of Article 11.10.5 require length to height ratios varying from 0.8H for low structures, i.e. 10.0 ft., to 0.63 H for high structures, i.e. 40.0 ft.
  
Significant shortening of the reinforcement elements below the minimum recommended ratio of 0.7H  may only be considered when accurate, site specific determinations of the strength of the unreinforced fill and the foundation soil have been made.  Christopher et al. (1990) presents results which strongly suggest that shorter reinforcing length to height ratios.  I.e. 0.5 H to 0.6 H , substantially increase horizontal deformations.
+
Significant shortening of the reinforcement elements below the minimum recommended ratio of 0.7H  may only be considered when accurate, site specific determinations of the strength of the unreinforced fill and the foundation soil have been made.  Christopher et al. (1990) presents results which strongly suggest that shorter reinforcing length to height ratios, i.e. 0.5 H to 0.6 H, substantially increase horizontal deformations.
  
 
:The reinforcement length shall be uniform throughout the entire height of the wall, unless substantiating evidence is presented to indicate that variation in length is satisfactory.
 
:The reinforcement length shall be uniform throughout the entire height of the wall, unless substantiating evidence is presented to indicate that variation in length is satisfactory.
Line 1,047: Line 1,427:
 
:A nonuniform reinforcement length may be considered under the following circumstances:
 
:A nonuniform reinforcement length may be considered under the following circumstances:
  
:Lengthening of uppermost reinforcement layers to beyond 0.7H  to meet pullout requirements, or to address seismic or impact loads.
+
:Lengthening of uppermost reinforcement layers to beyond 0.7H  to meet pullout requirements or to address seismic or impact loads.
  
 
:Lengthening of the lowermost reinforcement layers beyond 0.7H to meet overall (global) stability requirements based on the results of a detailed global stability analysis.
 
:Lengthening of the lowermost reinforcement layers beyond 0.7H to meet overall (global) stability requirements based on the results of a detailed global stability analysis.
 
 
 
 
:Shortening of bottom reinforcement layers to less than 0.7H  to minimize excavation requirements, provided the wall is bearing on rock or very competant foundation soil.
+
:Shortening of bottom reinforcement layers to less than 0.7H  to minimize excavation requirements, provided the wall is bearing on rock or very competent foundation soil.
  
 
For walls on rock or very competent foundation soil, e.i., SPT > 50, the Bottom reinforcements may be shortened to a minimum of 0.4H with the Upper reinforcements lengthened to compensate for external stability issues in lieu of removing rock or competent soil for construction.  Design Guidelines for this case are provided in FHWA Publications No. FHWA-NHI-00-043 (Elias et al. 2001).
 
For walls on rock or very competent foundation soil, e.i., SPT > 50, the Bottom reinforcements may be shortened to a minimum of 0.4H with the Upper reinforcements lengthened to compensate for external stability issues in lieu of removing rock or competent soil for construction.  Design Guidelines for this case are provided in FHWA Publications No. FHWA-NHI-00-043 (Elias et al. 2001).
  
For conditions of marginal stability, consideration must be given to ground improvement techniques to improve foundation stability, or to lengthening of reinforcement."
+
For conditions of marginal stability, consideration must be given to ground improvement techniques to improve foundation stability, or to lengthening of reinforcement.
  
 
MSE walls are pre-qualified and listed on the internet in two categories:
 
MSE walls are pre-qualified and listed on the internet in two categories:
Line 1,067: Line 1,447:
  
 
Combination wall systems are considered small block wall system and shall be battered with a maximum height of 10 feet.
 
Combination wall systems are considered small block wall system and shall be battered with a maximum height of 10 feet.
 +
<div id="Aesthetic enhancements may be used"></div>
 +
 +
Aesthetic enhancements may be used for either CIP or MSE walls. If [[#751.1.2.33 Aesthetic Enhancements|aesthetic enhancements]] are required by the district, form liners and concrete stains are encouraged rather than actual brickwork and stonework since form liners and concrete stains typically need less maintenance, less loading, less detailing, no extra support ledge and produce no risk of delaminations or falling work. However, for MSE large block walls only, form liners are required for all panels.  For additional information, see [https://epg.modot.org/index.php?title=751.24_LFD_Retaining_Walls#751.24.2_Mechanically_Stabilized_Earth_.28MSE.29_Walls EPG 751.24.2 Mechanically Stabilized Earth (MSE) Walls].
  
 
Any deviation from the criteria listed shall be discussed with Structural Project Manager.
 
Any deviation from the criteria listed shall be discussed with Structural Project Manager.
Line 1,072: Line 1,455:
 
===751.1.4.3 MSE Walls===
 
===751.1.4.3 MSE Walls===
  
Both the horizontal alignment and the top of wall elevations are supplied by the district in the Bridge Survey. You do need to check the top of wall elevations to make sure the district accounted for any concrete gutters placed behind the top of the wall.  These are necessary if the slope of the fill will direct water towards the top of the wall. The district should decide whether to use type A or type B gutters (Mo. Std. Plan 609.00) and where they should drain to.
+
Generally, both the horizontal alignment and the top of wall elevations are supplied by the district in the Bridge Survey. You do need to check the top of wall elevations to make sure the district accounted for any concrete gutters placed behind the top of the wall (Gutters are necessary if the slope of the fill can direct water towards the top of the wall, i.e. positive sloping and flat backfills). The district should decide whether to use Type A or Type B gutters ([https://www.modot.org/media/16880 Standard Plan 609.00]), or Modified Type A or Modified Type B gutters ([https://www.modot.org/media/16871 Standard Plan 607.11]) if fencing is required, and where they should drain (to be shown on roadway plans). For general guidelines, see [[751.24 LFD Retaining Walls#751.24.2 Mechanically Stabilized Earth (MSE) Walls|EPG 751.24.2 Mechanically Stabilized Earth (MSE) Walls]].  
  
You will also need to set the elevations for the top of the leveling pad.  The minimum embedment, which is the distance between the finished ground line and the top of the leveling pad, is based on this table: (FHWA Demo. #82)
+
You will also need to set the elevations for the top of the leveling pad.  The minimum embedment, which is the distance between the finished ground line and the top of the leveling pad, is based on this table: (FHWA Demonstration Project 82)
  
 
{|border="1" cellspacing="0" cellpadding="5" align="center" style="text-align:center"
 
{|border="1" cellspacing="0" cellpadding="5" align="center" style="text-align:center"
Line 1,087: Line 1,470:
 
|}
 
|}
  
The absolute minimum embedment is 2’.  When the soundings are returned, they will include a minimum embedment necessary for global stability.
+
The absolute minimum embedment is 2 ft.  When the soundings are returned, they will include a minimum embedment necessary for global stability.
  
Estimating the cost of MSE walls is quite simple.  Use $40 to $50 per square foot of the area of the face of the wall.
+
Preliminary cost estimating MSE walls is based on the unit price bid history and on the square footage of the area of the face of the wall.  The unit price per square foot of wall includes wall elements, leveling pad and backfill.  Excavation and retained fill are not included.
  
The request for soundings for MSE walls should include requests for the angle of internal frictions (Ø) for both the foundation and the retained material.  Request that soundings be taken every 25 feet along the wall alignment.  Soundings shall be made to rock or to a point which is 20 feet below the bottom of the wall, whichever is higher.
+
If soundings indicate weak material exist, then the designer should investigate that sufficient right of way limits exist to address the required length for the soil reinforcement.
  
If soundings indicate weak material exist then the designer should investigate that sufficient right of way limits exist to address the required length for the soil reinforcement.
+
For additional information, see [https://epg.modot.org/index.php?title=751.24_LFD_Retaining_Walls#751.24.2_Mechanically_Stabilized_Earth_.28MSE.29_Walls EPG 751.24.2 Mechanically Stabilized Earth (MSE) Walls].
  
 
===751.1.4.4 CIP Concrete Walls===
 
===751.1.4.4 CIP Concrete Walls===
  
Once you determine that you must use a CIP concrete wall, there is very little to do as far as the layout of the structure.  Both the horizontal alignment and the top of wall elevations are supplied by the district in the Bridge Survey.  You do need to check the top of wall elevations to make sure the district accounted for any concrete gutters placed behind the top of the wall.  These are necessary if the slope of the fill will direct water towards the top of the wall.  The district should decide whether to use type A or type B gutters (Mo. Std. Plan 609.00) and where they should drain to.
+
Once you determine that you must use a CIP wall, there is very little to do as far as the layout of the structure.  Both the horizontal alignment and the top of wall elevations are supplied by the district in the Bridge Survey.  You do need to check the top of wall elevations to make sure the district accounted for any concrete gutters placed behind the top of the wall.  These are necessary if the slope of the fill will direct water towards the top of the wall.  The district should decide whether to use Type A or Type B gutters ([http://www.modot.mo.gov/business/standards_and_specs/documents/60900.pdf Standard Plan 609.00]), or Modified Type A or Modified Type B gutters ([http://www.modot.mo.gov/business/standards_and_specs/documents/60711.pdf Standard Plan 607.11]) if fencing is required, and where they should drain to.
 
 
You will also need to set the elevations for the top of the footing, which should be a minimum of 2 feet below the finished ground line for walls south of Interstate 70 and 3 feet below the finished ground line for walls north of Interstate 70. In tight roadway situations where a barrier curb is to be placed on top of the wall, make sure that a stem thickness of 16" will fit.
 
 
 
Check with the District Contact to determine if they want any coping on the exposed face of the wall.
 
 
 
French drains will be used to relieve water pressure behind the CIP wall as a default. If you expect to encounter springs or swampy conditions, then check with the District Contact on calling for an underdrain. If the decision is made to use an underdrain, the porous backfill and pipes are Roadway Items and this must be noted on the Bridge Memorandum and Design Layout.
 
 
 
The request for soundings for CIP walls should include requests for the angle of internal friction (Ø) for the retained material as well as an allowable bearing value for the foundation.  Request that soundings be taken every 25 feet along the wall alignment.  Soundings shall be made to rock or to a point which is 20 feet below the bottom of the wall, whichever is higher.
 
  
A guide to estimating the costs of CIP retaining walls can be found on the following page. This is relatively accurate as long as you don’t need to place the wall on piling.  If you have indications that the foundation material is very poor in quality (less than 1 ton per sq. foot allowable bearing), add some money for piling.
+
You will also need to set the elevations for the top of the footing, which should be a minimum of 2 feet below the finished ground line for walls south of Interstate 70 and 3 feet below the finished ground line for walls north of Interstate 70. In tight roadway situations where a barrier or railing is to be placed on top of the wall, make sure that a stem thickness of 16 inches will fit.  
  
 +
Check with the district contact to determine if they want any coping on the exposed face of the wall.
  
{|border="1" cellpadding="2" cellspacing="0" style="text-align:center" align="center"
+
French drains will be used to relieve water pressure behind the CIP wall as a default.  If you expect to encounter springs or swampy conditions, then check with the district contact on calling for an underdrain.  If the decision is made to use an underdrain, the porous backfill and pipes are Roadway Items and this must be noted on the Bridge Memorandum and Design Layout.
|+'''Estimating Costs of CIP Retaining Walls'''
 
|Wall Height in Feet||Cost per Linear Foot
 
|-
 
|1||$75
 
|-
 
|2||$125
 
|-
 
|3||$175
 
|-
 
|4||$250
 
|-
 
|5||$270
 
|-
 
|6||$300
 
|-
 
|7||$325
 
|-
 
|8||$350
 
|-
 
|9||$450
 
|-
 
|10||$575
 
|-
 
|11||$650
 
|-
 
|12||$780
 
|-
 
|13||$860
 
|-
 
|14||$1,000
 
|-
 
|15||$1,080
 
|-
 
|16||$1,160
 
|-
 
|17||$1,200
 
|-
 
|18||$1,275
 
|-
 
|19||$1,440
 
|-
 
|20||$1,525
 
|-
 
|21||$1,610
 
|-
 
|22||$1,710
 
|-
 
|23||$1,790
 
|-
 
|24||$1,875
 
|-
 
|25||$1,975
 
|-
 
|26||$2,085
 
|-
 
|27||$2,185
 
|-
 
|28||$2,295
 
|-
 
|29||$2,395
 
|-
 
|30||$2,500
 
|-
 
|&nbsp;||&nbsp;
 
|-
 
|&nbsp;||&nbsp;
 
|}
 
  
Prices are sporadic beyond 30 feet in height.
+
For details on requesting soundings, see [[#751.1.2.20 Soundings (Borings)|EPG 751.1.2.20 Soundings (Borings)]].
  
Wall height is measured from the top of the footing to the top of the wall.
+
If you have indications that the foundation material is very poor in quality (less than 1 ton per sq. ft. allowable bearing), consider piling and include in the Preliminary Cost Estimate.  Preliminary cost estimating should follow [[751.1 Preliminary Design#751.1.2.18 Preliminary Cost Estimate|EPG 751.1.2.18 Preliminary Cost Estimate]] and be based upon unit price bid history.  More refined cost estimating should follow cost-basing estimating.
  
 
===751.1.4.5 Obstructions===
 
===751.1.4.5 Obstructions===
Line 1,207: Line 1,516:
  
  
[[Category:751 LRFD Manual General|751.01]]
+
[[Category:751 LRFD Bridge Design Guidelines|751.01]]

Revision as of 15:22, 21 September 2022

Forms
Structural Rehabilitation Checklist

Contents

751.1.1 Overview

751.1.1.1 Introduction

The Preliminary Design of a structure begins with the district submitting a Bridge Survey indicating their need for a structure, and ends with the completion of the Substructure Layout or TS&L submittal (type, size and location). This article is intended to be a guide for those individuals assigned the task of performing the Preliminary Design or “laying out” of a structure.

The types of structures can be broken into five categories:

1.) Bridge over Water
2.) Bridge over Roadway or Railroad
3.) Box Culvert over Water
4.) Retaining Wall (CIP walls taller than 5 ft., MSE walls adjacent to bridge end bents)
5.) Rehabilitation or Modification of Existing Structure

In addition to the following information, the Preliminary Design shall consider hydraulic issues where applicable.

751.1.1.2 Bridge Survey Processing and Bridge Numbering

The Preliminary Design process starts with the receipt of the Bridge Survey. The following is a list of steps that are taken by the Bridge Survey Processor.

Assign a Bridge Number to the Structure

The Bridge Division assigns bridge numbers in Bloodhound to all new, rehabilitated or modified structures (i.e., bridges, box culverts (see EPG 750.7.4.3 Summary of Responsibilities), CIP retaining walls over 5 ft. tall and MSE walls adjacent to bridge end bents).

Enter the Bridge Number, survey received date and feature crossed in the Bloodhound database.

New Structures:

New structures are numbered in ascending order using the next available bridge number. Numbering for new structures (except timber structures) start at A0001 thru A9999 and will be followed by B1000 thru B9999. (Note: B0001 thru B0581 were used for the Safe and Sound Bridge Replacement Program.)
New timber bridges are numbered in the same manner using the letter “T” instead of the letter “A”.

Temporary Structures:

Temporary bridges use the same number as the new bridge with the letter “T” added to the end (i.e., the temporary bridge for A8650 would be A8650T).

Rehabilitated or Modified Structures (Except when rehabilitation is only for structural steel coating):

Single Structures (Includes twin structures with individual bridge numbers):
Structures without a suffix letter on the existing bridge number will be numbered using the existing bridge number and a suffix number added that corresponds to the number of rehabilitations or modifications to the structure (i.e., bridge number A0455 becomes A04551 upon its first rehabilitation or modification and A04552 upon its second).
Single Structures with the Suffix “R”:
Structures that have the suffix “R” on the bridge number are usually bridges that have been rehabilitated or modified in the past, but in some cases bridges were given the suffix “R” to denote it as a replacement for a bridge with the same number. Review the existing bridge plans to determine if the “R” was for a rehabilitation or replacement. Structures that have been previously rehabilitated should replace the “R” with a suffix number corresponding to the total number of rehabilitations to the structure (i.e., bridge number A0444R would become A04442 (second rehab. or mod.), bridge number A0055R2 would become A00553 (third rehab. or mod.), etc.). For structures where the “R” denotes it as a replacement, the suffix number corresponds to the number of rehabilitations or modifications and the “R” is dropped (i.e., bridge number L0428R becomes L04281 for the first rehabilitation). If the “R” suffix was removed in a previous rehabilitation, the next suffix number is used regardless if the original structure was a rehabilitation or replacement.
Twin Structures with the Same Bridge Number:
Twin structures with the same bridge number will use a different suffix number for each structure. The numbering is similar to a single structure with the lower suffix number being used on the eastbound or southbound structure and the next suffix number being used on the westbound or northbound structure (i.e., bridge number A0144 would become A01441 for the eastbound bridge and A01442 for the westbound bridge. A future rehabilitation would become A01443 for the eastbound bridge and A01444 for the westbound bridge). Twin bridges with an “R” suffix on the bridge number would receive the suffix numbers using the same rules, but with the same consideration given to the “R” as it is for a single structure.

Structural Steel Coating (Use when all bridge pay items are related to structural steel coatings):

Rehabilitations that consist only of structural steel coatings use the existing bridge number plus the suffix “-Paint” (i.e., bridge number A2100 would become A2100-Paint and bridge number A150010 (multiple rehabilitations) would become A150010-Paint). A future rehabilitation consisting of only structural steel coatings would use the suffix “-Paint2” only if no other rehabilitations have been completed since the previous coating rehabilitation.

Removal of Existing Bridge Structures:

When a bridge structure is removed and not replaced by a new bridge structure or is removed under a separate contract, the suffix “-Remove” should be added to the latest bridge number (i.e., bridge number T0415 would become T0415-Remove and bridge number K01651 would become K01651-Remove).

Re-using Bridge Numbers:

Bridge numbers that were assigned to new structures that were never built are only reused if the proposed structure is at the same crossing location that the bridge number was originally assigned to.
Bridge numbers that were assigned to rehabilitate or modify structures where the work was not completed may reuse the previous bridge number by adding the suffix “-#2” to the bridge number (i.e., bridge number A6545 had plans developed for deck repairs and was assigned the bridge number A65451, but the work was never completed. At a later date, bridge A6545 is set up to be redecked; the bridge number assigned to the redeck would be A65451-#2). This suffix is only recorded in Bloodhound for tracking purposes and is not shown as part of the bridge number on file folders or final plans.


Create Job Folders

Check to see if a Correspondence File has been created. If the Correspondence File has been created, record the Bridge Number(s) in Bloodhound and make a Preliminary Design File for each structure received. If the Correspondence File has not been created, make a Correspondence File, an outer folder and a Preliminary Design File for each structure received. Here is the information for each type of folder/file:

Folder Type Required Information on Folder
Outer (pink label) County, Route and Job No.
Correspondence County, Route and Job No.
Preliminary Design County, Route, Bridge No., Location and Job No.

Also, be sure to notify by email the Structural Resource Manager and the appropriate Structural Project Manager or Structural Liaison Engineer, if known, when a new Correspondence File is created. The email subject line should include the Job No., County, Route and Bridge No. Include the name of the Bridge Division contact in the email, either the Structural Project Manager or the Structural Liaison Engineer.

Calculate Drainage Information

For structures over streams or waterways, calculate the drainage area and length of stream. Generate a drainage summary and include this information along with a map showing the drainage area for the structure and the area surrounding it in the Preliminary Design folder. If the drainage area is less than 1.5 sq. miles, consult the Structural Resource Manager to determine if preliminary design by the Bridge Division is necessary. The accuracy of the drainage area should be to the nearest 0.1 sq. mile for drainage areas less than 10 sq. miles and to the nearest 1 sq. mile for drainage areas greater than or equal to 10 sq. miles. When another stream intersects the subject stream near the downstream side of the proposed structure, create a separate drainage summary for the intersecting stream and include it in the Preliminary Design folder.

Process Electronic Files

When the electronic files listed in EPG 747.1.2 Bridge Survey Submittals are received, verify that the drawing scales are correct and that the necessary reference files are included. Also, review all Bridge Survey Sheets and the Bridge Survey Checklist for accuracy and completeness. The Bridge Survey Processor may have to work with the district to correct any discrepancies and/or omissions.

Add the newly assigned bridge number to the files and place a hard copy in the layout folder.

Final Step for Bridge Survey Processor

Once all of these steps are completed, the Bridge Survey Processor should deliver the Correspondence File, outer folder and the Preliminary Design Folder(s) to the Structural Resource Manager. An acknowledgement email is sent to the district contact(s) informing them that the Bridge Division has received the Bridge Survey. The email subject line should include the Job No., County and Route. Include the Bridge No(s). and the name of the Bridge Division contact in the email.

Once the survey is found to be complete and accurate, the Survey Complete date should be entered into Bloodhound. This date should match the Surv Rec date if no changes were made. If the survey is not complete or contains inaccuracies as submitted, we need to work with the district to fill in the blanks. If the omissions affect the timeline for completing the preliminary design, the Survey Complete date should reflect the date when we have all the information needed for the preliminary design to move forward without delay. If there is a delay in the bridge division review of the survey, this time should not count against the district in the survey complete date. The Bridge Survey Processor should work closely with the preliminary designer and SPM to determine the proper Survey Complete date in this case. For example, a bridge survey is received on 9/16/2016. Initial review by the bridge survey processor shows a complete survey. The job sits for five weeks while a preliminary resource comes available. Review by the preliminary designer shows a profile grade that is unusable and the preliminary design cannot progress until the grade situation is corrected. It takes four weeks for the grade to get worked out. The Survey Complete date should be four weeks after the Surv Rec date (10/14/2016). The district would not be penalized for our five week delay in reviewing the survey. This date is important because it will help us track when bridge surveys are turned in relative to when they are complete and when the project is due to Design.

751.1.1.3 Beginning Preliminary Design

The Preliminary Designer should meet with the Structural Project Manager to go over the Correspondence and Preliminary Design files to see if anything out of the ordinary has come up at Core Team Meetings prior to that date. It is important to include any correspondence or calculations used in the laying out of the structure in the bound portion of the Preliminary Design Folder.

The Preliminary Designer should then examine the Bridge Survey closely for any errors or omissions. Consult EPG 747 Bridge Reports and Layouts. Pay special attention to the scales used. Make sure the district's submittal includes photographs and details of staging and/or bypasses, if applicable. Verify that the proposed roadway width meets the NBI criteria for minimum bridge roadway width to avoid building a deficient bridge. Contact the district to resolve any discrepancies or questions.

A visit to the bridge site by the Preliminary Designer may be warranted to help determine Manning’s “n” values, examine adjacent properties, etc. If you decide to make this trip, advise the Structural Project Manager and the district contact since they may also want to attend.

Vertical Alignment and Bridge Deck Drainage

Laying out a bridge should consider deck drainage concerns for bridges on flat grades and sagging vertical curves and other vertical alignment issues as given in EPG 230.2 Vertical Alignment and EPG 230.2.10 Bridge Considerations.

751.1.1.4 Coordination, Permits, and Approvals

The interests of other agencies must be considered in the evaluation of a proposed stream-crossing system; cooperation and coordination with these agencies must be undertaken. Coordination with the State Emergency Management Agency (SEMA), the U.S. Coast Guard, the U.S. Army Corps of Engineers, and the Department of Natural Resources is required.

Required permits include:

  • U.S. Coast Guard permits for construction of bridges over navigable waterways.
  • Section 404 permits for fills within waterways of the United States from the U.S. Army Corps of Engineers.
  • Section 401 Water Quality Certification permits from the Missouri Department of Natural Resources.
  • Floodplain development permits for work in special flood hazard areas from the State Emergency Management Agency (SEMA).

Section 404 and Section 401 permits are obtained by the Design Division. U.S. Coast Guard permits are obtained by the Bridge Division. The Bridge Division will obtain floodplain development permits for projects that include structures in a regulated floodplain. The Design Division will obtain floodplain development permits for other projects involving roadway fill in a regulated floodplain.

Copies of approved U.S. Coast Guard permits and floodplain development permit/applications are sent to the district, with a copy to the Design Division.

See MoDOT and the Environment for more information on the required permits.

751.1.1.5 New Regular Bridge Design Schedule (Nonseismic) (Nonrailway Crossing)

751.1.1.5 Sept 28 2016.jpg

751.1.2 Bridges/Boxes

751.1.2.1 End Slopes/Spill Fills

The end slopes are determined by the Construction and Materials Division and are supplied to the Bridge Division by way of the Preliminary Geotechnical Report. If this report is not in the Correspondence file, contact the district to get a copy of it. The Bridge Division has made a commitment to the districts that we will have the bridge plans, specials and estimate completed 12 months after the date the Bridge Survey and Preliminary Geotechnical Report are received. The "12 month clock" does not start ticking until both the Bridge Survey and the Preliminary Geotechnical Report are in the Bridge Division.

When laying out a skewed structure, adjust the end slope for the skew angle. On higher skews, this will have a significant effect on the lengths of the spans. Often the slope of the spill fills will be steeper than the roadway side slopes. On a skewed structure, this makes it necessary to "warp" the slopes.

Whenever there will be a berm under any of the spans, its elevation should be such that there is a minimum of 4 feet clear between the ground line and the bottom of the girder as shown below.


751.1 Prelim Design Berm Elevation.gif
(*) Specify berm elevation or 4'-0" minimum clearance.
BERM ELEVATION


If a rock cut is encountered in the spill slope, a slope of 1:1 may be used to the top of the rock.

751.1.2.2 Wing Lengths

The purpose of wings is to contain and stabilize the abutment fill as the roadway transitions to the bridge. For stream crossings in particular, the wings also protect the abutment during extreme hydraulic events.

The lengths of the wings at the end bents are to be determined prior to the issuance of the Bridge Memorandum. There are two reasons for this. First, the district will use these lengths to determine the placement of their guardrail (bridge anchor section). Second, if the lengths of the wings exceed 22 ft., they will have to be broken into a stub wing and a detached wing wall. If this happens, then you will need to include this extra cost in your Preliminary Cost Estimate and request soundings for the wall. The request for soundings for the wall should include a request for the determination of the allowable bearing of the soil (if in cut - assume piling if it is in fill) and the angle of internal friction for the material retained by the detached wing wall. Also include the bottom of wing footing elevation.

In order to use a standard end section for Type D barrier on a short turned-back wing, consider increasing the wing length so that the barrier end section is at least 8 feet long.

Unequal Wing Lengths

Wing lengths at each end of a bridge could be unequal because of several factors: grade of roadway under, superelevation of bridge, skew of the bridge, and/or other ramps/roads/slopes adjacent to the bridge structure, e.g., stream access roads or unusual geomorphic conditions.

Set/determine the wing lengths using the control points, as shown in Embankment at Bridge Ends, which may be used for both grade separations and stream crossings. This is done after the end bent location is determined. If estimated wing lengths are within 3 ft., they should be made equal and based on the longer wing length. Make sure no slope is steeper than that recommended in the geotechnical preliminary report. Slightly flatter slopes are acceptable. The contractor will warp the slopes to fit the wing tip locations.

Equal wing lengths are preferable at stream crossings to mitigate scour, improve erosion control and improve/mitigate parallel water flow along wing and side embankment. Also, since wing lengths are reported to districts for use in estimating rock slope protection limits, unequal lengths (especially on the upstream side) could mistakenly lead to the unfavorable condition of allowing for less than adequate rock side slope protection.

Judgement is required since no two estimated wing lengths at a bridge end will be exactly equal. More often equal wing lengths are used.

On divided highway bridges with high skews and shallow end slopes, the wing lengths on the median side of the bridge may be less than the other side due to the difference in sideslope between the median and the outside.

751.1.2.3 Live Load Determination

The live load requirements for a structure shall be HL-93

On box culverts, the actual live load applied to the structure is dependent upon the amount of fill on top of the box; however, see Structural Project Manager for the live load that goes on the Bridge Memorandum.

751.1.2.4 Skew Angle

Determining the most appropriate skew angle for the structure involves some judgement. On bridges over streams, pick the angle that will allow floodwater to pass through the bridge opening with the least amount of interference from intermediate bent columns. Another consideration on meandering streams is to avoid a skew which will cause the spill fill – side slope transition from blocking the stream. Often a trip to the field may be justified just for determining the angle (you can even ask the district to stake some different skews for you to observe in the field).

On stream crossings, avoid skews between zero and five degrees and try to use five-degree increments. On grade separations, often the skew must be accurate to the nearest second to maintain minimum horizontal clearances.

Keep all bents on a bridge parallel whenever possible and avoid skews over 55 degrees (30 degrees for adjacent prestressed concrete beams). Also keep in mind that the higher the skew, the higher the Preliminary Cost Estimate due to the beam caps and wings being longer.

751.1.2.5 Bridge Width

For bridge width requirements, see EPG 231.8 Bridge Width.

751.1.2.6 Vertical and Horizontal Clearances

751.1.2.6.1 Grade Separations

Minimum Design Clearances for New Bridges
Facility Under Bridge Vertical Clearance under Superstructure1 Horizontal Clearance
Interstate and Principal Arterial Routes 16’-6” over roadway including auxiliary lanes and shoulders Clear zone clearances from the edge of the traveled way (includes shoulders and auxiliary lanes) are obtained from the District Design Division. The vertical clearance is required for the full width of the clear zone. Barrier is required if unable to locate obstacles outside clear zone (columns, beams, walls, coping, 3:1 [1V:3H] slopes or steeper). If a barrier is required the minimum distance to the barrier shall be specified on the Bridge Memorandum as the horizontal clearance otherwise the clear zone clearance shall be used. See EPG 751.2.2.6 Other Loads and Standard Plans 606.01, 606.51 and 617.10 for typical barrier and railing options.
Other State Routes with Volumes ≥ 1700 vpd 16’-6” over roadway including auxiliary lanes and shoulders
Other State Routes with Volumes < 1700 vpd 15’-6” over the roadway including auxiliary lanes and shoulders2
Other Streets and Roads 14’-6” (15’-6” commercial zones) over the roadway including auxiliary lanes and shoulders2
Railroads 23’-0” inside 18’-0” opening or as required by railroad (23’-4” for UPRR, 23’-6” for BNSF)3 14’-0” and 22’-0” from centerline4,5
(25’-0” eliminates collision walls)
1 Roadway vertical clearances are based upon AASHTO minimums with an additional 6 inches to accommodate future resurfacing of the roadway. An additional 1 ft. is required for pedestrian overpass facilities over roadways. Vertical clearances shown are also applicable when the facility under the bridge is being carried by a bridge.
2 To provide continuity of travel for taller vehicles exceptions can be made both rural and urban for any routes connecting to the systems where taller vehicles are allowed but not to exceed 16.5 feet.
3 Clearance is measured from the top of rails (from top of high rail on superelevated track). The required 18-ft. opening centered on the track shall be increased on each side of centerline 1.5 inches per each degree of curvature for any track crossed.
4 Fourteen feet is a preferred minimum. The absolute minimum is 9 ft. from the centerline plus 1.5 inches per each degree of any track curvature.
5 The minimum clearance of 22 ft. to be provided on one side of the track(s) is for off-track maintenance. If it is not obvious on which side of the track(s) this clearance is provided, a decision should be obtained from railroad's local representative. Assistance from Multimodal Operations may be required in some situations.
Clearance over Traffic During Construction (New and Existing Structures)
Roadways: Consult with the structural project manager or the structural liaison engineer and the district contact for minimum allowable vertical and horizontal clearance. Vertically this is usually 12 to 18 inches below the final minimum vertical clearance. Horizontally this is usually a minimum number of lanes or minimum size of opening required during the project while specifying the locality of the opening (e.g. centered on existing lanes, two 12-ft. lanes minimum in each direction, etc.).
These clearances shall be specified on the Bridge Memorandum to be used in the note required on the final plans. For note see EPG 751.50 A3. All Structures.
Railroads: If feasible, 15 ft. horizontally from centerline of track and 21.5 ft. vertically from tops of tracks (from top of high rail on superelevated track). If either of these clearances is not feasible then obtain acceptable clearances from the railroad projects manager. For the detail required on the final plans showing minimum clearances during construction over railroads, see EPG 751.5.2.1.2.7 Features Crossed.
Deficient Vertical Clearances on Interstates
Refer to EPG 131.1.7 Deficient Vertical Clearances on Interstates for information about coordinating minimum vertical clearance for grade separation structures with the Defense Department.

751.1.2.6.2 Stream Crossings

For vertical clearance on stream crossings, see EPG 748.3 Freeboard.

751.1.2.7 Structure Type Selection

Both steel and prestressed concrete girders shall be considered on all structure type selections. As the required span length of the structure increases to bridge the obstruction, deeper girder sections will be required. As a general rule of thumb, span to superstructure depth ratios (S/D) will be on the order of 20 to 30 with the higher numbers being slender, flexible structures.

Preliminary designers should consider these structure types as the span length increases with the top of the list providing the least amount of span capability. Economic consideration should be given to the selection of steel or concrete superstructures. Recent and relevant bid history for each structure type should be reviewed during the preliminary design phase.

  • Concrete Box Culvert (single, double or triple cell)
  • Prestressed or Reinforced Concrete Slab
  • Adjacent Prestressed Concrete Box or Voided Slab Beams (with approval of Structural Project Manager)
  • Shallow Depth Girder Sections: Wide Flange Steel Beams, Spread Prestressed Concrete Beams (Box or Voided Slab), Prestressed I-Girders (Type 2, 3, 4 or 6), or Prestressed NU-Girders (PSNU-35 or PSNU-43)
  • Intermediate Depth Girder Sections: Plate Girder, Prestressed Bulb-Tee Girder (63.5” or 72.5") or Prestressed NU Girder (PSNU-53, 63, 70 or 78)
  • Deep Girder Sections: Plate Girder (greater than 78” web depth)

Voided slab beams are currently only produced by one manufacturer and therefore a long transport may need to be considered in the bridge memo estimate.

Often site conditions warrant the use of shallower depth girder sections to maximize vertical clearance over roads or railroads or to maximize freeboard over streams. When contemplating these situations, the preliminary designer should work with the district highway designer to provide several structure depth options with corresponding roadway profile grade raises. It may be that a more expensive bridge structure results in an overall minimized project cost. High strength concrete or high-performance steel grades may allow the preliminary designer to span longer distances with shallower structures. These higher strength materials may also be used to eliminate girder lines as roadway width increases.

On multi-span structures, it is generally more efficient to have a balanced span arrangement where the end spans are approximately 10 percent shorter than the intermediate spans. This type of arrangement balances the positive moment demand at the midspans with the negative moment demand at the intermediate bents and allows optimization of the structural cross section. For example, a span layout of (67’ - 76’ - 67’) is structurally more efficient than (70’-70’-70’).

751.1.2.8 Box Culverts

Most districts prefer a box culvert to a bridge because of the lower maintenance costs; however, if a stream crossing is on the borderline between a box culvert and a bridge, each option should be explored and presented to the district. The presentation to the district should include the cost estimate for each option as well as a recommendation as to which option is preferred by the Bridge Division. Keep in mind that box culverts should be avoided on streams with medium to heavy drift. If the stream being crossed is a drainage ditch it is advisable to have the district contact the drainage district to see if they have any specific objections (i.e. drift etc.) to using a culvert at the proposed location. Approval of proposed structure layout by the drainage district may be required, see EPG 747.3.4 Bridge Permits or Approvals by Other Agencies.

751.1.2.8.1 Hydraulic Design

A general rule of thumb for the use of a culvert is that it can handle about 1,000 cfs per cell with 3 cells being the usual maximum. This can vary if the slope of the streambed is unusually flat or steep. Another rule of thumb is that the water from a drainage area of less than 5 square miles can usually be handled by a concrete box culvert. Curves or bends should be avoided when possible. See EPG 750.2.3.2.2 Head Loss Due to Bends when curves or bends will be used.

For details of hydraulic design, see EPG 750.2 Culverts.

Hydraulic designs and plans for some small box culverts are handled by the district. See EPG 750.7.4.3 Summary of Responsibilities for responsibility for analysis, design and final plans preparation.

751.1.2.8.2 Environmental Requirements

See EPG 750.7.3 Environmental Requirements for details of embedment, velocity and conveyance requirements.

751.1.2.8.3 Layout

751.1.2.8.3.1 Size

When sizing the proposed concrete box culvert, use Standard Box Culvert Sizes whenever possible. For information on standard box culverts sizes, see EPG 750.7.4.1 Standard Plans. For additional information on culvert size, see EPG 750.7.4.4 Size.

751.1.2.8.3.2 Length

The inside face of the headwall is located at the intersection of the roadway fill slope and the top of the top slab of culvert. Typically, the longest barrel is produced considering this intersection point upgrade. Flared inlets, varying roadway widths, clear zones and guardrail placement are possible exceptions to this rule.

When clear zones are provided, locate the inside face of the headwalls of the culvert at or beyond the edge of the roadway clear zone. In situations of very low fill, contact the district to determine if the use of guardrail is preferred to placing the headwalls beyond the edge of the clear zone. When clear zones are not provided the district will determine the need for guardrail on a case by case basis. Typically when guardrail is to be used over a culvert the typical section will show a 3’-5” shoulder widening as shown in Standard Plan 606.00. Consult the district if it is unclear whether adequate clear zones are provided or if guardrail is to be used over a box culvert. If the fill over the culvert is shallow, guardrail attachment may need to be provided. It may be advisable to lengthen culverts with shallow fill slightly to provide room for future guardrail attachments if guardrail over the box culvert is not provided.

751.1.2.8.3.3 Roadway Fill

Minimum roadway fill height is determined at the outside shoulder line and is the greater of 1 ft. or the thickness of the pavement and base material specified in EPG 750.7.11.1 Minimum Fill Heights. Pavement and shoulder widths and thicknesses are determined on a project by project basis. Pavement and shoulder details (i.e., width, thickness, alternate pavement options) can be obtained from the district if needed, but based on maximum pavement thicknesses and minimum shoulder widths, fill heights at the outside of the shoulder of 20 ½” or greater on major routes or 14 ½” or greater on minor routes will not require pavement or shoulder details. For more information on pavement and shoulder widths and thicknesses see Other Aspects of Pavement Design and EPG 231 Typical Section Elements of Roadways.

Roadway fill outside of the shoulders shall be warped (in the past this was referred to as the fill being “rolled up and over”) to provide a minimum of 12 in. of cover where the top of the culvert could be exposed. A standard note should be shown on the Bridge Memorandums (Memos) regarding warping the roadway fill. Cases where this could occur are:

1. Culvert ends with shallow fill and headwalls located outside of the clear zone.
2. Median of a divided highway with shallow fill.
3. Flared Inlets
4. Auxiliary lane or outer road with skews different than that of the mainline
5. Steep grade with a wide or skewed culvert.

For additional information of roadway fill, see EPG 750.7.11 Overfill Heights.

751.1.2.8.3.4 Fill Settlement

Check the Preliminary Geotechnical Report for recommendations concerning fill settlements and the use of collar beams on longer box culverts. Cambering of the culvert should also be considered when fill settlements are appreciable. For more information, see EPG 750.7.9 Camber in Culverts.

751.1.2.8.4 Precast Box Culvert Sections

If the use of precast box culvert sections will not be allowed to be substituted for cast-in-place construction or if precasting is required it should be noted on the bridge memorandum and on the bridge plans.

Precast option for box culvert extensions will be permitted using a cast-in-place connection where the centerline of new cells is not laterally displaced more than 15° (maximum) from the centerline of existing cells for each cell extension.

751.1.2.8.5 Abrasion

If a culvert requires design for abrasion it should be noted on the bridge memorandum. For more information see EPG 750.7.4.2 Abrasion of Interior Surfaces.

751.1.2.9 Girder Type Selection

Once it has been determined that the structure will have girders, the types of girders to be used must be identified. To check the vertical clearance or freeboard, the maximum span length of each type of girder must be known. See EPG 751.22 P/S Concrete I Girders or EPG 751.14 Steel Superstructure. Adjustments will need to be made if the span ratios become greater than 1.25.

If it is determined that the roadway profile grade will need to be raised (or lowered) to provide additional vertical clearance or freeboard, the preliminary designer should notify the district contact as soon as possible. It is best to provide the district with several options of varying profile grade elevation increase with varying structural depth. Larger grade elevation increases typically result in longer bridges as spill slopes dictate bridge length. The preliminary designer and district contact should work together to minimize the overall project cost even if the bridge cost is slightly more expensive. Consider the various structure types listed in EPG 751.1.2.7 Structural Type Selection when selecting the girder type. Also consider that adding girder lines or using higher strength material (concrete or steel) may allow longer or shallower spans for a given girder cross section. As a last resort, request a design exception for the substandard item.

751.1.2.9.1 Concrete Girder Options

Prestressed girder selection should use the following order for trial sizing and spanning:

Prestressed or reinforced concrete slab beams
Prestressed Concrete Box Beams
MoDOT Standard Prestressed Girders Type 2, 3, 4 and 6
NU Standard Prestressed Girders Type 35, 43, 53, 63, 70 and 78
MoDOT Bulb-Tees Type 7 and 8

For span lengths longer than 125 feet for prestressed concrete, the girders become very heavy and are difficult to transport to the site and often require two or more large cranes to place on the supports. The preliminary designer should discuss this with the district, and have it documented on the Constructability Questionnaire noted in EPG 751.1.2.18.3 Supporting Documents.

751.1.2.9.2 Steel Girder Options

When considering steel structures, the preliminary designer must decide if the girders should be painted or fabricated from weathering steel. If site-specific conditions allow, the use of unpainted weathering steel (ASTM A709 Grades 50W and HPS70W) should be considered and is MoDOT’s preferred system for routine steel I-girder type bridges due to its performance, economic and environmental benefits. Cost savings are realized because of the elimination of the initial paint system as well as the need for periodic renewal of the paint system over the life of the structure.

Weathering steels provide significant environmental and worker safety benefits as well. Since they do not require initial and periodic repainting of the whole bridge, emissions of volatile organic compounds (VOC) are reduced. Also, they generally do not require coating removal or disposal of contaminated blast debris over the service life of the structure. By eliminating the need for periodic repainting, the closing of traffic lanes can be prevented as well as the associated hazards to painters, maintenance workers, and the travelling public.

Partial coating of weathering steel is required near expansion joints. See EPG 751.14.5.8. Periodic recoating or overcoating will be required, however, on a much smaller scale than the whole bridge with the effect that lane closures and associated hazards are greatly reduced compared to painted steel.

Although weathering steel is MoDOT’s preferred system for routine I-girder bridges with proper detailing, it should not be used for box girders, trusses or other structure types where details may tend to trap moisture or debris. There are also some situations where the use of weathering steel may not be advisable due to unique environmental circumstances of the site. Generally, these types of structures would receive high deposits of salt along with humidity, or long-term wet conditions and individually each circumstance could be considered critical.

The FHWA Technical Advisory T5140.22 October 1989 should be used as guidance when determining the acceptability of weathering steel. Due to the large amounts of deicing salts used on our highways which ultimately causes salt spray on bridge girders, the flowchart below should be used as guidance for grade separations. The flowchart, Fig. 751.1.2.9, below, is general guidance but is not all inclusive. There may be cases based on the circumstances of the bridge site where the use of weathering steel is acceptable even though the flowchart may indicate otherwise. In these cases, follow MoDOT’s design exception process.

Fig. 751.1.2.9 Guidance on the Use of Weathering Steel for Grade Separations
* For multi-lane divided or undivided highways, consider the AADT and AADTT in one direction only.

Weathering steel may be used for stream crossings where 1) the base flood elevation is lower than the bottom of girder elevation and 2) the difference between the normal water surface and bottom of girder elevations is greater than 10 ft. for stagnant and 8 ft. for moving bodies of water. Where the difference in elevations is less than noted, weathering steel may be used upon approval of the Assistant State Bridge Engineer.

Additional documents that can be referenced to aid in identifying the site-specific locations and details that should be avoided when the use of weathering steel is being considered include:

1. Transporation Research Board. (1989). Guidelines for the use of Weathering Steel in Bridges, (NCHRP Report 314). Washington, DC: Albrecht, et al.
2. American Iron and Steel Institute. (1995). Performance of Weathering Steel in Highway Bridges, Third Phase Report. Nickerson, R.L.
3. American Institute of Steel Construction. (1993). Highway Structures Design Handbook (Vol. I, Chapter 9. Uncoated Weathering Steel Bridges). Pittsburgh, PA: Mathay, W.
4. MoDOT. (1996). Missouri Highway and Transportation Department Task Force Report on Weathering Steel for Bridges. Jefferson City, MO: Porter, P., et al.

The final brown rust appearance could be an aesthetic concern. When determining the use of weathering steel, aesthetics and other concerns should be discussed by the Core Team members, with input from Bridge Division and Maintenance Division.

If weathering steel cannot be used, the girders should be painted gray (Federal Standard #26373). If the district doesn’t want gray, they can choose brown (Federal Standard #30045). If the district or the local municipality wants a color other than gray or brown, they must meet the requirements of EPG 1045.5 Policy on Color of Structural Steel Paint. System H paint should be used on weathering steel while System G should be used on all other steel plate girders.

751.1.2.10 Longer Bridges

For bridges that are longer than normal (more than 6 spans being a general rule of thumb), other items must be considered. If the feature you are crossing allows flexibility in bent placement, the most cost-efficient span length is one that will result in the cost of one span's superstructure being equal to the cost of one bent. For example, calculate the cost of one intermediate bent, and then adjust the length of the span until the cost of the girders, slab and curb equal the cost of the bent. The use of higher strength concrete in Prestressed I-Girders or high performance steel in plate girders can allow spans to be increased approximately 20% as a means to eliminate intermediate bents.

Another item to consider is the placement of expansion devices. Be sure to include the costs of the expansion devices and deadman anchors (if applicable) in your Preliminary Cost Estimate.

751.1.2.11 Staged Construction

If the new structure being laid out replaces an existing structure on the same alignment, the default method of handling traffic during construction is to close the road and detour traffic. The new substructure should be spaced to avoid the existing substructure units if at all possible.

If the district determines the road cannot be closed, the options for handling traffic include staged construction or using a temporary bypass. If a temporary bypass is used, determine whether the district can size some drainage-diversion pipes for the bypass. If the district decides pipes cannot be used, then a temporary bridge is necessary and a separate Bridge Survey/Memo/Bridge No. is required.

If the district decides to use staged construction, one important item to verify in this situation is that the new girders will clear the existing substructure. Another item to consider in setting up the staging is the placement and attachment requirements of the temporary concrete traffic barrier relative to the bridge deck and meeting horizontal distance requirements from the edge of the deck, which determines whether the temporary concrete traffic barrier is attached to the deck and how it is attached.

751.1.2.12 Temporary Barriers

Bridge Plans must note whether temporary concrete traffic barrier is attached or freestanding, and if attached, whether they are attached with tie-down straps or bolt through deck attachment. Coordination is required with district Design. See EPG 617.1 Temporary Traffic Barriers for more guidance.

a. Where sufficient distance is available to accommodate lateral deflection of barriers: No attachment is required. Note on plans as “Freestanding” or “No attachment required”.
b. Where sufficient distance is not available to accommodate lateral deflection of barriers: Tie-down strap system is required. (Refer to Standard Plan 617.20.) Coordinate with district Design to provide a minimum of four connected temporary concrete traffic barrier sections on approach slab roadway.
c. Where lateral deflection cannot be tolerated: Bolt through deck system is required. (To be used only on existing decks that will be removed and that have sufficient strength.) (Refer to Standard Plan 617.20.) Coordinate with district Design division for required transition barrier attachments that may be used on any deck, existing or new, where lateral deflection is not permitted with approval of the Structural Project Manager or Structural Liaison Engineer.
751.1.2.12 Freestanding.jpg
Freestanding Temporary Barrier


For all other applications of a freestanding temporary concrete traffic barrier, the preferred installation method requires a 2 ft. buffer area behind the barrier to allow for lateral deflection in both work areas and lane separation situations.

Regardless of deflection distance (buffer area) available, if the bridge deck is super elevated or has a large roadway slope, a freestanding temporary concrete traffic barrier should not be used because the barrier has the potential for movement (“walking”) due to gravity forces and vibrations acting on the barrier.

When a temporary concrete traffic barrier is adequately attached to a bridge deck (refer to Standard Plan 617.20) a minimum distance of 6 in. shall be provided from the edge of the bridge deck to the face of the barrier.


751.1 Prelim Design Attached Temp Barrier.jpg
Attached Temporary Barrier

751.1.2.13 Earthquake (Seismic) Consideration

See EPG 756 Seismic Design for flowcharted seismic design requirements.

All new bridge/wall designs must meet Seismic Design Category A requirements which includes nonseismic (or static) designs unless the seismic design category is B, C, or D. If the structure you are laying out falls in Seismic Design Category B, C or D, there are a few items to keep in mind. Box culverts are preferable to bridges on stream crossings because they are exempt from seismic design unless crossing a known exposed fault. Pile cap intermediate bents are preferable to open column bents on footings because footings can grow quite large due to seismic forces. Minimize the number of expansion joints in the deck because each of these locations may require earthquake restrainers which are very costly. Make the superstructure as light as possible, which usually means use steel plate girders or wide flanges instead of prestressed concrete girders wherever possible.

Go to https://earthquake.usgs.gov/designmaps/us/application.php and use the following instructions to determine the LRFD Seismic Design Category:

Instructions:
1. For “Design Code Reference Document”, select “Derived from USGS hazard data available in 2002” followed by “2009 AASHTO”.
2. For “Site Soil Classification”, select “Site Soil Classification” (Select Site Class “A, B, C, D or E” for preliminary design per Geotechnical Section recommendation or for final design as given on Foundation Investigation Geotechnical Report.
3. For “Site Latitude” and “Site Longitude”, input coordinates or alternatively input address or zip code in the map area.

The new bridge design schedule for a seismic bridge requires 24 months minimum. See EPG 751.1.1.5 New Regular Bridge Design Schedule.

751.1.2.14 Temporary Bridges

If the district will be using a bypass on stream crossings, a temporary bridge may be necessary. The district should first consider using large drainage-diversion pipes to carry the water under the bypass, if the district determines this is not practical, they should submit a Bridge Survey for a temporary bridge on the bypass. Check with the Structural Project Manager for hydraulic design frequency.

Once the number of 40’ spans has been determined, the district should be contacted so they can locate the pieces necessary for the construction of the bridge. Make sure the pieces the district intends to use have the “new” beam caps that take 14” H-pile. The district should provide you with the location of where the pieces are coming from and where they should be taken by the contractor at the end of the project. If the district is unable to find the pieces, then they will need to be contractor furnished. This has a big impact on costs. See Preliminary Cost Estimate.

751.1.2.15 Bridges Over Railroads

Consult the AREMA (American Railway Engineering and Maintenance-of-Way Association) Manual for Railway Engineering located in the Bridge Division’s Development Section for more detailed information. Here are some basic points to keep in mind:

  • Railroads often raise their tracks so provide some cushion in your vertical clearance.
  • Absolute minimum horizontal clearance shall be 9 feet on each side of track centerline plus 1 1/2 inches per each degree of track curvature. (railroad projects manager of the Multimodal Operations Division will obtain the degree of curvature from the railroad)
  • Will the railroad want room for an extra track or maintenance roadway?
  • Keep the ballast free drained.
  • Drainage needs to be designed for 100-year storm.
  • Slope protection shall consist of Type 2, 18-inch thick rock blanket placed on top of permanent erosion control geotextile. Some railroads may require changes to this; however, this will be determined on a case-by-case basis.
  • Some railroads also now require the barrier and slab overhangs to be designed to accommodate fences that may be added in the future.

If the face of the columns of an intermediate bent is within 25 ft. of the centerline of the railroad track, a collision wall is required. If the face of the columns of an intermediate bent is within 12 ft. of the centerline the top of the collision wall shall be set at 12 ft. above top of rail otherwise the top of the collision wall shall be set at 6 ft. above top of rail.

The railroad projects manager in the Multimodal Operations Division is a very good resource for answering questions at any stage of the layout. It typically takes a very long time to receive approval of a layout from the railroad. The railroad must approve both the preliminary design and the final plans.

When making a submittal to the railroad project manager for approval of the preliminary design, include three sets of half-sized plat and profile sheets, as well as a copy of the Design Layout.

The new bridge design schedule for a railway crossing bridge requires 24 months minimum. See EPG 751.1.1.5 New Regular Bridge Design Schedule.

751.1.2.16 Historical Bridge Considerations

You also need to check with the Historical Bridge Coordinator in the Design Division when replacing a bridge. There is not a magic age for a bridge for it to become "historical". Age does not matter. All "Bridge Resources" that will be impacted by MoDOT need to be cleared through the Department of Natural Resources (DNR) Historic Preservation Program (HPP) before they can be replaced, demolished, extensively rehabilitated or deeded to a new owner (county, city, etc.). The following is a definition of "Bridge Resources":

"Bridge Resources are both public and privately owned highway, railroad and pedestrian bridges, viaducts and culverts. This does not include metal and plastic pipes, unless they are encased in an older concrete, stone or brick structure."

The following is the information on this topic supplied to the district (FYI):

"Bridge Resources on any given job or location study need to be checked out and cleared just like historic buildings (architecture) and archaeological sites. Standard size color photographs can be submitted to the Historic Bridge Coordinator directly and/or attached to the Request for Environmental Assessment (RES) or Questionnaire to Determine Need for Cultural Resources Assessment. The Historic Bridge Coordinator will then determine and execute procedures for clearance, if required."

Bridges that are older than 50 years stand a better chance of being evaluated as eligible for the National Register of Historic Places (NRHP) in Clayton Fraser's 1996 draft Missouri Historic Bridge Inventory. This is a study that was undertaken under STURAA (Surface Transportation and Uniform Relocation Assistance Act of 1987) in order to inventory all potentially NRHP eligible historic bridges in the state. Any of these that are determined NRHP eligible by the HPP will require special mitigation (or avoidance) if they are to be affected by project activities. For this reason, it is important that all bridge resources be identified early in the process.

Usually, bridge resources do not stand in the way of right of way acquisition (A-dates) because they are generally located on roadways that the state already owns; however, there are cases in which bridge resources are privately owned and located on private property. In these rare cases, bridge resources would need to be checked out prior to our right of way acquisition approval.

751.1.2.17 Preliminary Cost Estimate

The Preliminary Cost Estimate should be neat, legible and dated since a copy of it is included with the Bridge Memo. It should also be rounded to the nearest thousand dollars.

The accepted method of calculating the Preliminary Cost Estimate is to calculate some approximate quantities for the bridge and then multiply them by the unit prices supplied by the Bridge Division Preliminary and Review Section. A spreadsheet should be used to calculate these quantities. To estimate the pounds of reinforcing steel in a structure, multiply the number of cubic yards of concrete in the structure by 125 for bridges. See table below for Box Culverts.

Table 751.1.2.17,
Box Culvert Reinforcing Steel (lbs.) Estimate
Design Fill (ft.) Concrete (lbs/cy) Multiplier
2.00 225
6.00 168
10.00 116
25.00 96
32.00 84

The Preliminary Cost Estimate should be increased for the following items: Cost Estimate Guide for rural preliminary design (do not compound the increases by using your judgment).

Item % Increase
Staged Construction 10
Horizontally Curved 5
Seismic Performance Cat. B 10 *
Seismic Performance Cat. C 25 *
Seismic Performance Cat. D 40 *
Tight Site/Limited Access 3


These factors assume estimated quantities have not been increased due to seismic forces.


Some guidelines for estimating the cost of the removal of existing bridges include:

Type of Bridge Removal Cost per Square Foot
Simple Structures Over Streams **
Girder Structures Over Roads **
Conc. Slab Structures Over Interstates **
   (quick opening of lanes to traffic)
Consult Bid Tabs for an analysis of the latest bridge removal costs. Bridge Division staff may consult the Pay Item Spreadsheet maintained by the Structural Preliminary and Review Engineer.

751.1.2.18 Bridge Memorandums

Bridge Memorandums are generated for new and rehabilitated bridge structures including retaining walls. Formal correspondence will not be required for special structural work or miscellaneous structures like high mast tower lighting (HMTL) or small retaining walls equal to or shorter than 5 feet; however, documentation such as a Bridge Memorandum may be a good idea in order to effectively communicate the understanding and agreement to the level of design work proposed and associated construction costs with districts.

751.1.2.18.1 Purpose

The Bridge Memorandum is the instrument which coordinates bridge plan and roadway plan preparation. It is sent to the district to inform them where we plan to put the bridge, what kind of structure it will be, what the Preliminary Cost Estimate is and any other pertinent information. More information is required on more complicated structures. If you are not sure if the district needs to have a certain piece of information concerning the structure, include it on the Bridge Memorandum to be safe. Too much information is better than too little.

An electronic copy of the bridge memorandum and supporting documents are sent to the district for review and signature. If, during the design process, revision to the bridge memorandum by either the district or the Bridge Division becomes necessary, all parties to the memorandum are to be notified immediately. The proposed revisions must be agreed to by all parties that signed the original bridge memorandum.

The Bridge Memorandum also serves as a design layout for structures where the latter is not required, see EPG 751.1.2.31 Finishing Up Design Layout.

751.1.2.18.2 Content

Bridge Memorandum Examples
Highway Grade Separation
(Minor Route over Major Route)
Railroad Grade Separation
(Minor Route & Priority EQ Route)
Stream Crossing (Bridge)
(Low Volume Route)
Stream Crossing (Culvert)
(Minor Route)
Bridge Rehabilitation
(Minor Route)
Bridge Rehabilitation
(Major Route and Major Bridge)
Retaining Wall

Sample listing of what to include on the Bridge Memorandum:

1. Identify the following classifications if applicable: (Design Implications)

• All routes involved shall be classified as either:
o (major), as shown in link.
o (minor), not a major route and ADT ≥ 400.
o (low volume), not a major route and ADT < 400.
• Major bridges with a total length ≥ 1000 feet shall be classified by specifying “(major)” behind the specified bridge number.
• Priority 1 or 2 earthquake emergency routes shall be classified by specifying “(priority 1 2 EQ)” behind the route classification.

2. Identify type of structure, span lengths, skew, loading, roadway width, wing lengths and special end fill considerations. For curved structures, specify how the design span lengths are to be measured i.e., “measured along the CL of Roadway”. If plate girder or wide flange beam, further identify them as either weathering or painted steel.

3. Indicate all pertinent profile grade, alignment and superelevation transition information.

4. Identify the fill exception stations or ends of the bridge. The district uses this to coordinate the bridge with their roadway design features such as guardrail. For PSI-Girder bridges, take into account the layout length when calculating these stations.

5. Identify slopes at end bents.

6. Indicate elevation of any berms to be constructed at the end bents.

7. If applicable, call for old roadway fill to be removed to natural ground line.

8. For box culverts, indicate the location of the headwalls and the type of wings to be provided (flared or straight). Also include the upper and lower flow line elevations along the CL of the box.

9. Identify any bridge related items that the district will need to address in their plans or special provisions as a “Roadway Item”.

10. Include the cost estimate for construction (Preliminary Cost Estimate).

11. Include the method of traffic handling while construction is underway. Attach sketches for staged construction when appropriate.

12. For stream crossings, show all pertinent hydrologic data used for the layout of the structure. See EPG 751.5.2.1.5.3 Hydraulic Data for Hydraulic Data tables.

13. For roadway and railroad grade separations, include all minimum vertical and horizontal clearances (final and construction) and include the opening (horizontal limits) of the minimum vertical clearance. The minimum horizontal clearance shall be specified from the edge of the traveled way(s).

14. Quite often, the district will add items to a bridge late in the final design process because they “didn’t think of them” earlier. This often causes extra work due to the necessary redesigns. Include a statement similar to the following to reduce this occurrence:

  • "No conduit, lighting, utility supports or sidewalks are to be included in the final plans for this bridge."
  • If the district has already indicated that they want special items attached to the bridge, include the specifics on the Bridge Memorandum and modify the above note.

15. The design year AADT (annual average daily traffic) and AADTT (annual average daily truck traffic). Request this from the district if it is not shown on the plat sheet. On grade separations, get the AADT and AADTT for both roads.

16. For box culverts, always include the following notes:

  • Channel bottom shall be graded within the right of way for transition of channel bed to culvert openings. Channel banks shall be tapered to match culvert openings. (Roadway Item)
  • If any part of the barrel is exposed, the roadway fill shall be warped to provide 12 inches minimum cover. (Roadway Item) (See EPG 751.1.2.8.3.3, Box Culverts, Roadway Fill.)

17. Also for box culverts, state if guardrail (Roadway Item) is to be provided in lieu of meeting the clear zone requirements. If there will be guardrail over the box culvert and the fill height is less than indicated in EPG 750.7.4.5, Box Culverts, Guardrail Attachment, indicate that attachment of the guardrail to the top slab will be handled in the bridge plans, even though the guardrail itself is a roadway item. For additional information on when to use guardrail attachments, see EPG 751.1.2.8.3.2 Length, Box Culvert, Length.

18. For stream crossings (new structures, widened structures and rehabs where the waterway opening is reduced.) include a statement stating that a Floodplain Development Permit is required or that a Floodplain Development Permit is not required and that the Bridge Division will request such a permit if necessary. Also indicate the flood hazard zone (i.e., A, A1, B) and whether or not the bridge is in a Floodway.

19. On Rehabilitated and widened structures give the current and proposed load rating and load posting as well as the current condition ratings for the deck, superstructure, substructure and scour.

20. Identify the bridge approach slab class major or minor. If a design exception is required or approved, then note accordingly. Identify asphalt mix type (determined by district) when the asphalt bridge approach slab sub-class is an option.

21. Identify the bridge end drainage provisions as determined by district Design. For example, note when concrete aprons at each wing wall will be required (Rdwy. Item). Note when concrete approach pavement (Rdwy. Item) with or without drain basins (Rdwy. Item) will be required, or note when rock blanket will be required that extends up to full length of bridge approach slabs, or when drain flumes (Rdwy. Item) will be required.

22. For redecks or in other cases where the rock blanket elevations are not shown on the bridge plans and the top of the rock blanket is required to be flush to the existing ground line in accordance with the Memorandum of Agreement with SEMA, include the following note:

The top of rock blanket shall be flush to the ground line as directed by the engineer. (Roadway Item.)

23. For retaining walls, indicate any aesthetic treatments such as concrete staining and form liner requirements. Be specific regarding names, types and colors of staining, and names and types of form liner.

24. Form liners are standard for MSE large block walls. Be specific regarding names, types and colors of staining, and names and types of form liner. See Bridge Standard Drawings – MSE Wall - MSEW.

25. For MSE wall abutments: Identify gutter type, fencing, lower longitudinal and lateral drain pipe sizes (type and sizes to be determined by district Design division). (Lateral drain pipes are only required as determined by district Design division.)

26. OPTIONAL Seismic Information for new bridge or wall on Memo: Note “Preliminary Seismic Description: Site Class _, Seismic Design Category _, As = __, SD1 = _” that would require Geotechnical Section input regarding the Site Class and Seismic Design Category used for cost estimating. (This is similar to item no. 9 under EPG 751.1.2.31 Finishing Up Design Layout.)

27. For rehabs, redecks, widenings, recoatings and new replacement structures, see EPG 751.1.3.9 Environmental Considerations: Asbestos and Lead for notes to include.

751.1.2.18.3 Supporting Documents

Supporting documents may provide additional information to the district or request additional information from them. Other documents may need to be included, but at a minimum the following documents should be sent to the district with the Bridge Memorandum:

751.1.2.18.4 Bridge Division Review

Once the Preliminary Designer has the Bridge Memo and supporting documents completed, they are submitted to the Structural Project Manager (SPM) for their review. The SPM will then request a Bridge Memo Conference with the Assistant State Bridge Engineer, the Structural Resource Manager and the Structural Prelim. & Review Engineer. After the review and conference, the Preliminary Designer will update the Bridge Memorandum and supporting documents. The Designer and SPM sign and date the memo by typing their names and the date in the locations provided.

751.1.2.18.5 Bridge/District Agreement Process

The following process will be used to establish agreement between the district and Bridge Division on Bridge Memorandums:

1) Bridge Memorandums and supporting documentation will be made available on SharePoint by Bridge Division.
2) The Bridge Division preliminary designer or Structural Project Manager (SPM) will email the Transportation Project Manager (TPM) and the District Bridge Engineer a link to the Bridge Memorandum in SharePoint when the memorandum is ready for review by the district. (A link to the Constructability Questionnaire, Cost Estimate, Layout for Soundings, and Request for Soil Properties may also be included.) As part of their review the TPM should forward the Bridge Memorandum to the appropriate Resident Engineer to solicit their input on the Memorandum.
3) Changes to the Bridge Memorandum should be made in revision mode or with bold blue text for additions and red strikethrough text for deletion of existing text. (Discussion of proposed changes with the Bridge Division preliminary designer and SPM is recommended before making changes.)
4) Once the district’s review of the Bridge Memorandum is complete the approving district personnel should type their names, titles and the date in the appropriate locations.
5) TPMs or their designees email the Bridge Division preliminary designer and SPM to inform them the district has reviewed and signed the Bridge Memorandum. A summary explaining any of the changes should be included in the email.
6) The Bridge Division preliminary designer or SPM will accept the changes or coordinate with TPMs or their designees to resolve any differences.
7) Once all differences are resolved the Bridge Division preliminary designer or the SPM will email the TPM or the TPM's designee indicating the agreement process is complete. Changes made to the Bridge Memorandum after the initial agreement may be handled by email or by the process described above.

751.1.2.18.6 Documentation

The Bridge Memorandum, supporting documents and related correspondence will be stored on the Bridge Division SharePoint page in the Projects -Inwork directory.

A copy of the agreed upon bridge memo is placed in the Layout folder. If changes are made after the initial agreement, a copy of the revised memo should be added to the layout folder and the original bridge memo marked as void with the date of revision noted.

751.1 Prelim Design Bridge Memo (Ex 1).gif

751.1.2.19 Soundings (Borings)

Additional Information
Request for Final Soundings for Structures Form
Guidance for Request for Final Soundings for Structures Form

751.1.2.19.1 Purpose

The borings define subsurface conditions at the project site and are used to determine type of foundation (driven piles, pile cap footing, spread footings, drilled shafts), preliminary estimate of pile lengths and engineering design properties.

Note that two types of soundings are typically provided by a soundings investigation.

1. Auger Borings - These are the most typical type of soundings provided due to availability of equipment and low cost. This type of boring is generally stopped immediately upon encountering "hard rock". All description of type of soil and rock encountered is determined in the field.
2. Core Samples - These are more time consuming and expensive. They are also subject to the availability of the specialized equipment and are therefore provided as sparingly as possible by the soundings crew. Once "hard rock" is encountered at a coring location, drilling is continued for an additional 10 ft. to ensure a consistent layer of actual hard rock (not a boulder). If a void layer is encountered in the additional drilling, the drilling is continued until another 10 ft. of consistent hard rock is encountered. In addition to field determination of soil layer type and performance of the Standard Penetration Test (SPT), samples are returned to the lab for additional tests such as determination of rock quality (% RQD).

751.1.2.19.2 Required Locations

Bridges – Borings should be requested at each bent. For bents on columns, estimate the number and location of the columns for each bent and request borings for these locations.

Box Culverts – Borings should only be requested for Box Culverts on Rock (no bottom slab). Borings should be requested every 10 ft. along the alignment of both exterior walls for single box culverts and along both the exterior and interior walls for multiple cell culverts.

MSE Walls – Borings should be requested at 25 ft. intervals along the baseline of the MSE Wall and at control points along the wall (such as bend lines). For a MSE Wall that wraps around an end bent, consideration should be given as to whether requesting additional borings in a grid pattern between the walls is necessary.

CIP Concrete Retaining Walls – Borings should be requested at 25 ft. intervals along the wall alignment.

751.1.2.19.3 Required Documents

Plan and Elevation/Profile Sheets. Using MicroStation, the proposed structure should be drawn on the bridge survey plan sheet(s). Boring symbols should be placed at all requested boring locations.

To find the Northing and Easting, the "Label Coordinates" tool in MicroStation can be used. The grid factor, projection factor, coordinate system, zone, horizontal datum and vertical datum will be required information necessary for completing the Request for Final Soundings for Structures Form, all of which should have been provided with the bridge survey report.

Plan and Elevation Sheet(s) of Existing Bridge. When applicable.

Request for Final Soundings for Structures Form. The Guidance for Request for Final Soundings for Structures Form is available.

Instructions to Soundings Party included on the form should be similar to the following:

Bridges – Provide cores at alternating locations with one core per bent. Where rock is not encountered at core sampling locations, make standard penetration tests at 5 ft. depth increments. If rock is encountered at these core locations, provide RQD determinations at 5 ft. depth increments. If a sounding location is not accessible, please provide an alternative sounding as close as possible to the requested location in order to get an accurate representation of soil conditions at the bent line.
Box Culverts – Provide cores at each location to determine depth and quality of rock. Information will be used to determine structure type (concrete box on rock – without bottom slab) and excavation quantities. If rock is unsuitable for concrete box on rock, discontinue core and sound depth to rock. If sounding location is not accessible, provide an alternate sounding as close as possible to the requested location in order to get an accurate representation of soil conditions along proposed culvert wall.
Retaining Walls - Request that soundings be taken every 25 ft. along the wall alignment. Soundings shall be made to rock or to a point which is 20 ft. below the bottom of the wall, whichever is higher.

Request for Soil Properties – The request for soil properties is located on a separate tab in the Request for Final Soundings for Structures form.

Bridges – If there is a possibility that drilled shafts will be used, request borings based on using drilled shafts so the appropriate lab work can be done the first time.
MSE Walls – The request for soundings for MSE walls should include requests for the angle of internal frictions (Ø) for both the foundation and the retained material.

Due Date – Use the following guidelines when setting a due date:

Project Time Line Foundation Report Due Date
< 10 Months Contact Geotechnical Section1
≥ 10 Months 13 Weeks from Submittal Date
1 Preferred due date should be discussed at the memo conference and the Geotechnical Section contacted to establish a due date.

751.1.2.19.4 Submittal

The completed Request for Final Soundings of Structures form and the other supporting documents listed above should be stored on the Bridge Division SharePoint page in the Projects-Inwork directory under the structure’s subfolder. (Consultants should contact the Structural Liaison Engineer).

A request for soundings should be sent by email to the Construction and Materials Division. The email shall be addressed to the Geotechnical Engineer and copied to the Geotechnical Director and the Structural Project Manager (or the Structural Liaison Engineer). It should include at a minimum, a link to the SharePoint folder that contains the completed Request for Final Soundings of Structures Form and supporting documents. In addition to the SharePoint link, any relevant information that may aid the Geotechnical Section in providing the requested borings should be included.

The request for soundings is typically done at the same time that the Bridge Memorandum is sent to the district.

751.1.2.20 Substructure Type

Once the signed Bridge Memo and the Borings are received, the entire layout folder should be given to the Preliminary Detailer (requested by SPM, assigned by Structural Resource Manager). The Preliminary Detailer will copy the appropriate MicroStation drawings into their own directory. (Do not rename files) Consultants contact Structural Liaison Engineer. The Preliminary Detailer will then draw the proposed bridge on the plat and profile sheets. The bridge should also be drawn on the contracted profile for a perspective of the profile grade relative to the ground line for drainage considerations. The Preliminary Detailer will also generate a draft Design Layout Sheet and then return the layout folder to the Preliminary Designer for review.

The Preliminary Designer will then choose the substructure types for each of the bents. Pile cap bents without concrete encasement are less expensive than column bents but they should not be used at the following locations:

Where drift has been identified as a problem
Where the height of the unbraced piling is excessive and kl/r exceeds 120 (kl/r<120 is generally preferred) (take scour into account)
Where the bent is adjacent to traffic (grade separations)

Encased pile cap bents may be considered if economical. Embed concrete encasement 2 ft. (minimum) below the top of the lowest finished groundline elevation, unless a greater embedment is required for bridge scour. Greater embedment up to 5 or 6 ft. may be considered in situations where anticipated ground line elevation can fluctuate more severely. (Be sure to account for excavation quantities for deeper embedment.) Provision for encasing piles may be considered at the following locations:

Where drift is a concern and protection is required
Where larger radius of gyration is necessary and therefore improved buckling resistance for locations where the exposed unbraced column length is large
Not exclusively where the piles at the pile/wall interface may experience wet/dry cycles and/or excessive periods of ground moisture

For column bents, an economic analysis should be performed to compare drilled shafts to footings with cofferdams. When evaluating the drilled shaft option, keep in mind that if casing is used (see Geotechnical information) it should extend at least as high as the elevation that would be used for the seal course design. Also keep in mind that the permanent casing should be kept at least one foot below the ground line or low water elevation. Any casing above this elevation will be temporary.

End Bents are usually pile cap bents; however, if quality rock is abundant at or just below the bottom of beam elevation, a stub end bent on spread footings may be used. If you have any doubt about the suitability and uniformity of the rock, you can still use a pile cap end bent. Just include prebore to get a minimum of 10 ft. of piling. If you have concerns about temperature movements, you can require that the prebore holes be oversized to allow for this movement.

For any pile cap bents, where steel piles are to be placed near a fluctuating water line or near a ground line where aggressive soil conditions exist or anticipated to exist in the future, corrosion can result in substantial material loss in pile sections over time, either slowly or rapidly. Galvanized steel piling is required for all new pile cap bents to be used as a deterrent to both accelerated and incidental pile corrosion as commonly seen in the field. Further, conditions like known in corrosive soils, some stream crossings with known history of effects on steel piles and grounds subject to stray currents, these conditions should affect the decision of whether pile cap bents can be effectively utilized. The potential effects of corrosion and the potential deterioration from environmental conditions should always be considered in the determination and selection of the steel pile type and steel pile cross-section (size of HP pile or casing thickness), and in considering the long-term durability of the pile type in service.

Once the substructure type has been determined, re-examine your Preliminary Cost Estimate and notify the district if it needs to be adjusted.

Galvanized Steel Piles

Galvanizing shall be required for all steel piles. Utilizing galvanized steel piles and pile bracing members shall be in addition to the requirements of Standard Specifications Sec 702 except that protective coatings specified in Sec 702 will not be required for galvanized piles or galvanized bracing members.

Where galvanized steel piling is expected to be exposed to severe corrosive conditions, consideration can be given to increased steel pile thickness or consideration of a reduced loaded steel area for bearing, or conditions mitigated to prevent long term corrosivity risk . This equally applies to the potential corrosion and early deterioration of permanent steel casing used for drilled shafts though they are not required to be galvanized. For all cases, further consideration beyond normal practice should be given to investigating corrosion protection, rate of corrosion as it relates to steel thickness design and expected service life including galvanizing losses, corrosion mitigation or different substructure support in order to meet a 75 year or longer design life. For additional information refer to LRFD 10.7.5 and 10.8.1.5. Consult with the Structural Project Manager or Structural Liaison Engineer to determine options and strategy for implementation.

All Bridge and Retaining Wall Piles (For Example, abutment piles, wing wall piles, intermediate pile cap bent piles and pile cap footing piles)

All surfaces of piles shall be galvanized to a minimum galvanized penetration (elevation) or its full length based on the following guidance. The minimum galvanized penetration (elevation) shall be estimated in preliminary design and finalized in final design. The minimum galvanized penetration (elevation) or full length will be shown on the design layout.

Guidance for determining minimum galvanized penetration (elevation):

The designer shall establish the limits of galvanized structural steel pile (i.e., HP pile and CIP pile). All exposed pile plus any required length below ground shall be galvanized. Based on required galvanized pile length determine and show Minimum Galvanized Penetration (Elevation) or Full Length on the Design Layout and on the plans.

Required Pile
Galvanizing
For Nonscour
Required Pile
Galvanizing
For Channel Scour
Required Pile
Galvanizing
For Channel Migration
Estimated Pile Length ≤ 50 feet Full Length of Pile Full Length of Pile Full Length of Pile
Estimated Pile Length > 50 feet 20 feet (in ground)1 20 feet (in ground)1, but not less than 5 feet below max. scour depth. 20 feet (in ground)1, but not less than 5 feet below stream bed elev.
1 “In ground” is measured from finished ground line on intermediate bents, and bottom of beam cap for abutments.

For retaining walls supported on piles, the minimum galvanized penetration (elevation) for piles shall be “Full Length of Pile” for estimated pile length up to 50 feet and 15 feet below bottom of wall for estimated pile length greater than 50 feet.

For bridge end bents on piles with embankments supported by MSE walls, the minimum galvanized penetration (elevation) for piles shall be “Full Length of Pile” for estimated pile length up to 50 feet and 15 feet below top of leveling pad for estimated pile length greater than 50 feet.

Temporary Bridge Piles

Protective coatings are not required in accordance with Sec 718. Galvanized pile is not required. All HP piles driven to rock shall require pile point reinforcement.

751.1.2.21 Type of Footings

Once it has been determined that a bent will have columns on footings, the next decision is whether the footings should be pile or spread (on shale or rock). If it is a stream crossing, the bottom of footing elevation should be based on the scour calculations found in EPG 750.3 Bridges, an article dealing with hydraulic design. The borings should then be studied to see if a minimum of 10 ft. of piling can be placed below the footings. If this is doubtful because of the presence of shale or rock, spread footings or drilled shafts should be used. In instances where it appears that a spread footing can be used but there are pinnacles in the area, you may want to use a pile footing and just require prebore to ensure that you get the minimum embedment of 10 feet. For spread footings on grade separations, include a “not above” elevation to ensure a footing cover of at least 3 feet.

751.1.2.22 Types of Piling

The two types of piling commonly used are structural steel HP pile and close-ended steel pipe pile (cast-in-place, CIP). Open ended steel pipe pile (cast-in-place, CIP) can also be used. HP piles are commonly used as end bearing piles when shale or rock will be encountered at an elevation that will limit the pile lengths to about 100 ft. or less. CIP piles are commonly used as friction pile for which a minimum tip elevation must be determined (see EPG 751.36.2 Steel Pile for criteria). All HP piles driven to rock shall require pile point reinforcement. For CIP pile, Geotechnical Section indicates either "No Pile Point Needed" or "Pile Point Needed" and recommends pile point type on boring log. “Cruciform” or “Conical” pile point reinforcement is allowed for closed ended CIP pile. “Manufactured open ended cutting shoe (inside flange)” pile point reinforcement is allowed for open ended CIP. Generally pile point reinforcement is needed for CIP pile if boulders, cobbles or dense gravel are anticipated. For all piles, prebore if necessary to achieve minimum embedment.

Here are some guidelines for minimum embedment:


Pile Type Minimum Embedment
Structural Steel HP-Pile 10' into natural ground
15’ into natural ground at integral end bents(1)(2)
10’ below bottom of MSE wall leveling pad
15'-20' below scour depth(4)
CIP Steel Pipe Pile 10' into natural ground
10’ below bottom of MSE wall leveling pad
15’ into natural ground at integral end bents(1)(3)
15'-20' below scour depth(4)
(1) 10’ is allowed if piles are designed using a rigorous design procedure.
(2) When precore into rock is necessary to provide the minimum 15’ embedment, a minimum precore of 5’ is required. (i.e., 12’ of soil over rock will require a 17’ pile embedment)
(3) When prebore is required, pile shall be embedded at least 15’ below prebore hole.
(4) 15’ if the material is hard cohesive or dense granular; 20’ if the material is soft cohesive or loose granular.


See EPG 751.24.2.1 Design for further guidance on pile embedment behind MSE Walls.

751.1.2.23 Estimating the Lengths of Piles

All designers doing preliminary design should use the bearing graph provided in the foundation investigation Geotechnical report to estimate the lengths for piling. If a bearing graph is not provided the designer should perform a static analysis.

One way to check the validity of your static analysis results is to look at the piling information for existing bridges in the vicinity. Please also be on the lookout for any borings that contain "glacial till" (gravelly clay). This material is notorious for stopping pile.

This procedure is not a substitute for experience and engineering judgment. It is simply an attempt to have a more uniform method for estimating pile lengths.

All soil data must be obtained as well as elevation information pertaining to intermediate and end bents. The soil borings and core information are then observed. The unit weights of the different soil layers are determined by correlating information from the core data with information found in reference tables. The resulting unit weights are written on the soil boring page. If the soil is cohesive, the undrained shear strength should be determined by dividing the results of the pocket penetrometer test by two. If there was no pocket penetrometer test performed, then a correlation between the SPT blow counts and the undrained shear strength can be determined from reference tables. The water table must be identified or estimated and labeled on each of the borings and cores. The water table is usually distinguishable by the presence of gray colored soil. Note that more accurate data is obtained from cores than is obtained from borings because borings are performed using an auger type apparatus that mixes and remolds the soil.

751.1.2.24 Drilled Shafts

Drilled shafts are to be used when their cost is comparable to that of large cofferdams and footings. Other examples include when there are subsurface items to avoid (culverts, utilities, etc.) or when there are extremely high soil pressures due to slope failures.

The Foundation Investigation request should include a request for opinion regarding the necessity of permanent casing when drilled shafts are investigated.

Cost estimate savings and supporting subsurface information shall be discussed with Construction and Materials before permanent casing is omitted on a project.

The Foundation Investigation Geotechnical Report (or soundings report) for drilled shafts should supply you with the nominal end bearing (tip resistance) and side friction (side resistance) as well as the elevations for which the nominal rock values are applicable.

The Design Layout Sheet should include the following information:

Top of Drilled Shaft Elevation
Top of Permanent Casing Elevation
Anticipated Tip of Casing Elevation
Anticipated Top of Sound Rock Elevation


Bent Elevation Side Friction (tsf) End Bearing (tsf)
       

751.1.2.25 Excavation Datum

An Excavation Datum should be placed on the Layout Sheet when water is expected to be encountered during the excavation for footings. The elevation used is usually the Low Water Elevation plus 1 foot (rounded up to the next even foot) but may be made slightly higher on bigger streams and rivers. Everything above this datum is Class 1 Excavation while everything below it is Class 2 Excavation.

751.1.2.26 Seal Courses

On structures over water with pile footings, a determination should be made as to whether or not to include seal courses. Seal courses are used in conjunction with cofferdams when a contractor may have trouble dewatering the footing excavation. They are usually necessary when you have sandy or gravelly soils and footing elevations below the stream bed. You will need to include a water surface elevation on the Design Layout Sheet for which the Seal Courses should be designed for. Typically the elevation used is the average of the Low Water Elevation and the Design High Water Elevation; however, a site visit may be required to determine how reasonable this is. In no case should this elevation be higher than the 10 year high water elevation or the overbank elevation.

751.1.2.27 Cofferdams

Cofferdams should be included if the depth of the hole for the footing exceeds 8 feet and/or the bottom of footing elevation is below the Ordinary High Water (OHW) elevation. Any bent that requires a seal course will also require a cofferdam. These are bid lump sum per bent. Consult with the Assistant State Bridge Engineer about this. All piling in pile footings should be straight (not battered) when a cofferdam is expected.

751.1.2.28 Webs

On structures over water where medium to heavy drift has been indicated on the Bridge Survey, consider using web walls between the columns on the column bents near or in the stream. The bottom elevation for the web is typically 1' higher than the overbank elevation.

751.1.2.29 Protection of Spill Slopes and Side Slopes

The district shall be consulted for type of slope protection. Either Concrete Slope Protection or Rock Blanket can be used for grade separations and are Roadway Pay Items. On stream crossings, Rock Blanket is usually placed. The type and thickness of Rock Blanket is to be determined by the district based on the flow velocity from the Scour design flood frequency. This flow velocity is determined by the person doing the hydraulic calculations and should be placed on the Bridge Memorandum. Permanent erosion control geotextile is always required to be placed under rock blanket.

When Rock Blanket is used, an elevation for the upper limit of this protection needs to be calculated. First, calculate the following two elevations:

100 year High Water Elevation plus 2 feet
500 year High Water Elevation plus 1 foot

Take the higher of these two elevations and compare it to the Low Girder Elevation minus 1.2 feet. Use the lowest of these two elevations for the upper limit of your Rock Blanket. This elevation should be placed on the profile sheets.

If the toe of the abutment slope falls on the overbank, the rock blanket apron should extend from the toe toward the channel a distance equal to twice the 100 year flow depth on the overbank, but need not exceed 25 feet.

Note: District Design has the option of extending rock blanket up to and for the full length of the bridge approach slab or otherwise using drain flumes for bridge end drainage. See EPG 503 Bridge Approach Slabs, EPG 611 Embankment Protection and Standard Plan 609.40.

751.1.2.30 Design Exceptions

Anytime MoDOT standards are not followed, a Design Exception is necessary. These are usually initiated by the Transportation Project Manager in the district; however, if the item is related to the bridge, the Bridge Division will initiate the Design Exception.

The Design Exception Information should be filled out by the preliminary designer and then reviewed by the Structural Project Manager (SPM). A complete explanation of the basis for the design variance must be provided, including cost justification and details on how the variance will affect adjacent properties. The SPM should then submit the Design Exception to the Assistant State Bridge Engineer for review. After this review, the Design Exception should be submitted to the State Bridge Engineer for the Sate Bridge Engineer's signature. This submission should include written comments from the SPM on why the Design Exception should be approved. Once the Design Exception has been signed by the State Bridge Engineer, the SPM should mail the Design Exception Information Form and cover letter to the Transportation Project Manager in the district. The TPM will sign it and then send it to the General Headquarters Design Division for final approval. The Design Division will supply copies of the signed Design Exception to both the district and the Bridge Division.

Some examples of Design Exceptions initiated by the Bridge Division are:


Hydraulic Standards

These include not meeting the standards for freeboard, design frequency, etc.


Vertical Clearance

If the vertical clearance under a new or widened bridge does not meet the standard, a Design Exception is required. If the reduction in vertical clearance is due solely to the overlay of the road under the bridge, the Bridge Division would not initiate the Design Exception.


Roadway/Shoulder Width Less Than Standard (New Structures)

On new structures, if the roadway and/or shoulder widths on the bridge match the approach roadway, the Design Exception would be initiated by the district. If the roadway and/or shoulder widths on a new bridge are less than the approach roadway, the Design Exception would be initiated by the Bridge Division.


Roadway/Shoulder Width Less Than Standard (Existing Structures)

On Non-Interstate Rehab (3R) jobs, an exception for width is required any time we don’t meet the new design standards. The approach lanes being referred to in the rural design standards note (8) are the new lanes. The last note should be modified to read “Bridges programmed for replacement within 5 years may be allowed to remain in place as is and should be looked at on a case by case basis.”

On Interstate Rehab (4R) jobs, an exception for width is required any time we don’t meet the new design standards. If an existing bridge is over 200 feet long, FHWA has said that they will routinely approve the width if both shoulders are at least 3.5’ wide, but we should still request the Design Exception. FHWA will want to see any approved Design Exceptions before they approve the preliminary design.

Bridge Approach Slabs (New Bridges)

On new bridges, the interchangeability of bridge approach slab classes will require a design exception. For example, if a Bridge Approach Slab (Major) is to be substituted for a Bridge Approach Slab (Minor), a design exception will be required and initiated by the Bridge Division based on project core team consensus.

751.1.2.31 Finishing Up Design Layout

Design Layouts shall be generated for new bridges, retaining walls and when foundation work is required for bridge widenings. Otherwise, Design Layouts are not utilized for conveyance of information related to rehabilitation projects, or work on existing bridges or, more generally, on structures.

Once the Preliminary Detailer has created the Design Layout Sheet and added the borings and details of the proposed bridge to the plat and profile sheets, they should be checked by the Preliminary Designer. These sheets are the end product of the Preliminary Design process and will be used to perform the structural calculations for the Final Design phase of the bridge, which results in the production of the contract plans. Here is a list of items to include.

1.) General Information
  a. Route and structure classifications
  b. Live load designation
  c. Traffic counts for the design year (AADT and AADTT).
  d. Tie station (if applicable).
  e. Beginning station.
  f. Horizontal curve data.
  g. Profile grade information (including offset from CL of roadway or median).
  h. Excavation datum.
2.) Superstructure
  a. Type and span lengths.
  b. Roadway widths and type of barrier or railing.
3.) Substructure
  a. Skew(s) of all bents.
  b. Types of all bents.
  c. Type and locations of sway bracing for concrete pile cap intermediate bent with HP pile.
  d. Locations and top of wall elevations for collision walls.
  e. Embedment of encasement for encased pile cap bent.
  f. Location of tie beam.
  g. Bottom elevations of web beam.
4.) End Bents (Abutments)
  a. Type of end fill and maximum slope. Include earth plugs for piling in rock fill.
  b. Berm elevations.
  c. Type and extent of spill and side slope protection (permanent erosion control geotextile fabric is required).
  d. Bridge end drainage provisions per district (drain basins1, rock blanket, drain flumes) (Rdwy. Item)
  e. Angle of internal friction to be used for deadman anchors.
5.) Foundations
  a. Type and lengths of all piling.
  b. Minimum galvanized penetration (elevation)
  c. Minimum tip elevations for all piles.
  d. Location and elevation for any preboring.
  e. Pile point reinforcement (shoes) required for all structural steel HP piles. When Geotechnical Section indicates pile point reinforcement needed and show pile point type on boring log for CIP pile, then recommended pile point reinforcement type shall be shown on Design Layout.
  f. Types of footings, their elevations and allowable bearing (if applicable).
  g. Location of any cofferdams and/or seal courses.
  h. End bearing and side bearing capacity for any drilled shafts.
  i. Top of Rock Socket elevations and their minimum lengths.
  j. Estimated Maximum Scour Depth (Elev.)2
  k. Minimum pile cleanout penetration (Elev.)3
6.) Traffic Handling
  a. How will traffic be handled (bypass, road closure, staging, other)
  b. Include a sketch of any staging.
7.) Disposition of Existing Structure
  a. Bridge No(s). of structures slated for removal.
  b. Estimate cost of removal and indicate that this cost is included in the total.
8.) Hydraulic Information
  a. Drainage area and terrain description.
  b. Design frequency.
  c. Design discharge.
  d. Design high water elevation.
  e. Estimated backwater.
  f. Overtopping frequency and discharge if less than 500 yr.
9.) Seismic Information (New Bridge or Wall) (Applies to both dynamic and static designs)
  a. Site Class, Seismic Design Category, As, SD1
  b. Either “LRFD Seismic Details Only” or “LRFD Complete Seismic Analysis”
  c.

For Nonseismic (or static) designs, Seismic Design Category A, As, SD1 (All new designs must meet SDC A. See EPG 751.1.2.13 Earthquake (Seismic) Consideration.)
10.) Miscellaneous
  a. Locations of Bridge Approach Slabs.
  b. Call out slab drain requirements if other than the standard procedure.
  c. The location of the stationing reference line (CL roadway, CL median, other).
  d. Station equations.
  e. Minimum final and construction clearances (vertical and horizontal).
  f. Use of weathering steel or color of paint (steel girders).
  g. Name and phone number of district contact.
  h. Preliminary Cost Estimate.
  i. Details of any utilities to be attached to the bridge.
  j. Details of any conduit, light supports or any other unusual attachments.
  k. Channel change requirements.
  l. Temporary shoring requirements and whether it is a Bridge or Roadway Item.
  m. Location of Maint. facility contractor is to use for delivery of MoDOT retained items.
  n. Directory/path for any Ceal, Geopak or MicroStation files used for layout of bridge.
  1 Drain basins can be included with concrete approach pavement per district. (Rdwy. Item)
  2 Show maximum of total scour depths estimated for multiple return periods in years from Preliminary design which should be
    given on the Design Layout. Show the controlling return period (e.g. 100, 200, 500) in Foundation Data. If return periods are different for different bents, add a new line in Foundation Data.
On the plans report note EPG 751.50 E2.22 for CIP pile.
  3 Show for open ended CIP piles.


Once the Preliminary Detailer and Designer are in agreement on these items, the entire layout folder should be submitted to the SPM for their review. The SPM will then request a Design Layout Conference with the Assistant State Bridge Engineer and the Structural Resource Manager.

Following this conference, the Preliminary Detailer and Designer will make any requested changes and complete the assembly of the Layout Folder by including the approved Design Layout Sheet and one set of half sized plat and profile sheets. The Layout Folder should then be delivered to the SPM along with one set of half-sized plat and profile sheets and a copy of the Design Layout Sheet.

The SPM should then use a cover letter to send the one set of half-sized plat and profile sheets, as well as the copy of the Design Layout Sheet, to the Transportation Project Manager in the district. Include in this cover letter any changes in the Preliminary Cost Estimate and the current Plans Completion Date. An example can be found on the next page.

The Preliminary Detailer should provide a copy of the Design Layout Sheet to the Bridge Survey Processor. The Bridge Survey Processor should then perform the following tasks:

  • Enter the Date to Final Design in the Bridge Survey Book and the Survey Rcv. Database
  • Supply a copy of the Design Layout Sheet to Development and Review.
  • Copy all of the MicroStation files in house to
  • pwname:\\MoDOT\Documents\Central Office\Bridge\A_Prelim_design\district\job no.
  • (Consultants contact Structural Liaison Engineer).

The SPM should then enter the following information into Bloodhound:

All other fields in Bloodhound should be updated at this time by the SPM.

The SPM will then send a request for a Final Designer to the Structural Resource Manager.

751.1.2.32 FHWA Submittal

Federal involvement is determined in accordance with EPG 123.1.1 FHWA Oversight – National Highway System. Projects which are delegated for federal involvement for preliminary design on the PODI matrix must be submitted to FHWA for approval.

The submittal should include the following:

  • Cover letter
  • One set of half-sized plat and profile sheets
  • One copy of Design Layout Sheet
  • One copy of completed Bridge Survey Report
  • One copy of the Borings report including Cover Letter from Materials
  • One copy of each approved Design Exception (if applicable)
  • One copy of the Bridge Deck Condition Survey Summary (if applicable)
  • One copy of the Bridge Rehab Checklist (if applicable)
  • One copy of the Bridge Inspection Report for the existing bridge (if applicable)
  • One copy of half-sized existing bridge plans (if applicable)
  • One copy of anything else referred to on the Design Layout Sheet (an example would be top of pavement elevations if these are to be used in Final Design)


That is the end of the Preliminary Design phase of bridge design at MoDOT.

751.1.2.33 Aesthetic Enhancements

Aesthetic enhancements can include everything from form liners and different colored paints to actual brick or stonework on the bridge. The district is required to inform the Bridge Division if aesthetic enhancements will be required on a bridge. Aesthetic enhancements should be discussed by the core team during the scoping process.

Note: Galvanized slab drains are to remain unpainted unless otherwise requested by the district. The required special provision is available if the district wishes to paint the galvanized slab drains.

Specifying Form Liners

Form liners are typically supplied in 4 ft. wide sections. Consideration should be given to specifying concrete work in 2 ft. increments to avoid waste of form liner. Use of 1 ft. increments may be possible. Avoid specifying work requiring less than 1 ft. increments of form liner without approval of the Structural Project Manager or Structural Liaison Engineer. Specifying work requiring form liner using other than 4 ft. increments may affect cost and should be reviewed.

751.1.2.34 Blast Loading Considerations

Consideration should be given to the blast loading provisions given in AASHTO LRFD Bridge Design Specifications and AASHTO Bridge Security Guidelines for major bridges only and with the approval of the State Bridge Engineer.

Requirements for provision of blast loading protection and for structural design should be documented on the Bridge Memorandum and Design Layout.

All documentation associated with consideration of and requirements for blast loading protection and/or structural design including structural design computations should be detached or separated from other publicly available documents and marked “Not for Public Consumption.”

751.1.2.35 Bridge Approach Slabs

See EPG 503 Bridge Approach Slabs.

751.1.2.36 Bridge End Drainage

See EPG 503 Bridge Approach Slabs.

751.1.3 Wearing Surfaces/Rehabs/Redecks/Widenings

751.1.3.1 Overview

Modifying existing bridges is quite different from laying out new bridges. Bridge wearing surfaces (overlays), rehabs, redecks and only widenings when the substructure is not being widened require the preparation and approval of a Bridge Memo as the only official written document requiring signatory approval (see EPG 751.1.2.19 Bridge Memorandums) as a matter of procedure. A Design Layout is not required in these instances. However, bridge widenings when substructure and foundation work are required will require procedurally both a Bridge Memo and a Design Layout for signatory approval since soundings for exploring subsurface conditions will be required for the foundations.

These types of projects can be broken into four general categories:

  1. Adding a wearing surface to an existing bridge as part of a roadway overlay project.
  2. Rehabilitating and/or redecking an existing bridge as a stand alone programmed project.
  3. Widening an existing bridge to meet minimum shoulder width requirements as part of a roadway overlay project.
  4. Widening an existing bridge to add lanes as part of a roadway project.

751.1.3.2 Documentation

A structural rehabilitation checklist shall be required for determining the current condition and documenting all needed improvements regardless of budget restraints. It is critical to control future growth in project scope or cost overruns during construction that is checklist captures all needed repairs using accurate quantities corresponding to contract bid items. Staff responsible for filling out checklist should contact the Bridge Division if assistance is needing in correlating deterioration with appropriate contract bid items.

A deck test is not required but may be useful in determining the most appropriate wearing surface for bridges with deck ratings of 5 or 6.

A pull off test is not required but may be useful in determining the viability of polymer wearing surface.

Both deck tests and pull off tests are performed by the Preliminary and Review Section.

A Bridge Memorandum shall be required for documenting proposed construction work and estimated construction costs for district concurrence.

A Design Layout shall be required only for widening projects where there is proposed foundation construction.

751.1.3.3 Bridges on Resurfacing Projects

This is probably the most common type of project. The first step is to determine the limits of the project. This can be done by looking at the description and log miles of the project in the Program Book. The district contact should also be consulted to make sure the project limits have not changed. The second step is using the Bridge Maps produced by the Maintenance Division to locate any and all bridges within the limits of the project.

Once the Bridge Nos. for these structures are known, obtain a copy of the Bridge Maintenance report for each structure. These reports contain the log mile for each structure. Compare this to the log mile limits of the project. If the log mile on the report indicates the bridge is outside of the project limits, check with the district contact again to see if the bridge is to be included in the project.

If a bridge falls within the project limits, it must be evaluated to see if it meets the current safety criteria for such items as shoulder width and curb type/height. If the job will be built with federal funds, any substandard safety item must be remedied or handled with a design exception. If the job will be built with 100% state funds, the bridge can be left alone (no safety improvements).

751.1.3.4 Barrier or Railing Type, Height and Guidelines for Curb Blockouts

AASHTO LRFD uses the term “railing” to refer to all types of bridge traffic barrier systems used on bridges. MoDOT uses the term “barrier” for solid concrete bridge railing (single-faced on the edge of roadway and dual-faced medians) and the term “railing” for barrier systems consisting of a rail(s) and supports. Several types of barrier and railing are acceptable for use on bridges in Missouri (see Common Bridge Barrier and Railing); thrie beam railing, Type A, B, C, D, G and H barrier; curb and parapet barrier, two tube rail; or FHWA MASH or NCHRP 350 approved crash tested barrier or railing meeting TL-4 rating as given on the FHWA Bridge Railings website.

While meeting MASH TL-4 requirements is preferred, existing barrier or railing may be used in place if meeting NCHRP 350 TL-3 or TL-4 requirements, or existing barrier or railing may be retrofitted to meet same requirements. See Common Bridge Barrier and Railing (for Rehabilitations) for further guidance.

New bridge barrier or railing on existing bridges shall meet MASH TL-4 requirements on major routes with design speeds greater than 45 mph. Similarly, MASH TL-4 barrier or railing is required on minor and low volume routes with design speeds greater than 55 mph or AADT ≥ 1700. New bridge barrier or railing on existing bridges for all other major, minor, and low volume routes may instead meet MASH TL-3, NCHRP 350 TL-4 or NCHRP 350 TL-3 requirements where circumstances restrict the use of a MASH TL-4 barrier or railing. In any case, the new barrier or railing shall not be rated lower than the existing barrier or railing. The hierarchy for crash test ratings in descending order is listed below with qualified barriers and railings in Missouri:

  • MASH (2016) TL-4 (Type C and D barrier)
  • MASH TL-3 (Type H barrier, Type A and B barrier)
  • NCHRP 350 TL-4 (two tube railing, 12” x 29” vertical barrier)
  • NCHRP 350 TL-3 (thrie beam railing).

Type C and D barrier shall be used on all redecks, rehabs and widenings where the full length of barrier is being replaced with exceptions for the following:

  • sight distance concerns. Type H barrier or two tube rail is recommended.
  • rating concerns where the weight of the barrier prohibits its use or causes impractical restrictions or costs for the project. Type H barrier or two tube rail is recommended.
  • roadway width restrictions. Two tube rail or thrie beam rail is recommended.

The approach railing does not need to match the test level of the bridge barrier or railing. MoDOT standard approach rails typically do not rate higher than TL-3.

When using a concrete barrier, a five-hole bolt pattern shall be used for connecting the approach railing to the bridge barrier.

Bridge barrier or railing on single lane bridges may be used in place if for no other reason than the grade is not being raised. Thin wearing surfaces measuring no more than 3/8 inch will not be considered as raising the grade.

Thrie Beam Railing (Bridge Guardrail)

If the deck is less than 8½ inches thick, the attachment must bolt through the deck with a plate on the bottom side of the deck. In the past, MoDOT used details where a bent stud was formed within the deck. This is no longer acceptable because of observed failure in thin decks where the edge can break off and the bottom of slab can pop out during a collision.

The center of the thrie beam shall be a minimum of 21 inches to the top of the finished driving surface.

Thrie beam railing shall not be installed on new or replacement bridges or widenings. Thrie beam shall not be used for grade crossings or other areas where drainage over the side of the deck is a concern.

Type A, B, C, D, G and H Barriers

If installed at the same time as the driving surface, the top of the barrier shall not be less than 32 inches above the driving surface.

If a wearing surface is installed after the barrier is in place, the wearing surface thickness shall not be made greater than that whereby the barrier height is made less than 30 inches , i.e. the final grade with wearing surface installed shall not increase more than 2 inches.

If an existing wearing surface is replaced next to Type A or B barrier, the new wearing surface thickness shall not be made less than that where by the height above the driving surface of the break between the upper and lower slope of the barrier is made greater than 13 inches.

Curb and Parapet Barrier

The concrete portions of the curb and parapet are the only components used in determining the height of the barrier for establishing if the system meets current standards or is substandard. The handrails are not crashworthy and therefore are not considered as part of the height of the barrier.

Curb and parapet were typically constructed 27 inches measured from the driving surface to top of parapet.

Sections of curb and parapet may be replaced without consideration of upgrading.

When a wearing surface is to be applied, the height of the existing curb and parapet system shall be determined from the existing driving surface and if necessary shall be heightened to 32 inches or 36 inches above the proposed driving surface based on Guidelines for Curb Blockout, immediately below. Increasing the height of an existing curb and parapet is generally done by adding a blockout to the curb and parapet (i.e., curb blockout).

Guidelines for Curb Blockout

Background and Application

Guidelines were developed considering Practical Design concepts (refer to EPG 143 Practical Design).

Guidelines apply to bridges to be resurfaced and/or rehabilitated that have concrete curb and parapet barrier. They do not apply to bridges on Contract Leveling Course projects that are in accordance with EPG 402.1 Design of Leveling Course Projects.

When resurfacing and rehabilitating a bridge, consideration shall be given to upgrading the curb and parapet barrier by increasing the overall height if the barrier does not meet criteria given in these guidelines. The guidelines are based upon reviewing conditions that require satisfying height and horizontal parapet offset requirements using the minimum height of 27 inches in accordance with 2002 AASHTO 17th Edition and earlier editions and a maximum horizontal parapet offset of 6 inches from curb face to parapet face which is a MoDOT requirement (EPG 128 Conceptual Studies, 3R-Rural Design Criteria recommends a 6-inch brush curb). Upgrades to curb and parapet should be made by constructing a curb blockout. The following guidelines describe circumstances where it is, or is not, necessary to upgrade curb and parapet that were either originally built substandard or made substandard due to an earlier wearing surface or will be made substandard due to a proposed wearing surface.

Guidelines

Look at the 5-year history of accidents on the bridge (beginning log mile to ending log mile).

If there were any accidents in this time period that involved a vehicle striking the curb, then curb and parapet not meeting current standards should be upgraded to meet the current (2016)MASH TL-4 requirement which is to increase the height to 36 inches. A 32” blockout height will be allowed, upon approval of the SPM or SLE, when either sight distance or weight restrictions are a concern.

If there were NOT any accidents in the 5-year history AND if the grade is not being raised then it shall not be necessary to upgrade the curb and parapet.

If the accident history or grade criteria are not met, then it shall be necessary to upgrade the curb and parapet. The district may submit a design exception to eliminate a curb blockout for bridges not on major routes and with AADT < 1700 when there is no history of accidents on the bridge and the grade is being raised no more than 2 inches from the 27-inch minimum height requirement.

Limiting Wearing Surface Thickness To Meet Guidelines

The wearing surface thickness can be limited to that which would not cause the curb and parapet height to become substandard. An exception to this is a 1/4 to 3/8-inch height tolerance to allow for the possibility of placing a thin wearing surface on a bridge with an existing standard 27-inch high curb and parapet as measured from the original driving surface to the top of the parapet. Adding a thin wearing surface will not by itself make a satisfactory curb and parapet railing height substandard as reviewed and approved by MoDOT and FHWA. For overlay projects, where a curb blockout is already in place, the final blockout height shall not be less than 30 inches.

Note: In all cases, the allowable wearing surface thickness would also be dependent on a structural review to confirm that the weight of the wearing surface would not lead to overstresses or an unacceptable posting.

Details

The horizontal offset (or ledge) from the curb face to the parapet face is recommended to be between zero and 3 inches but shall not exceed 6 inches. If a curb blockout is used, the ledge shall not exceed 3 inches.

End posts are not always the same width as the parapets. If the end posts are wider and if they extend towards the driving lanes, it shall be necessary to remove the end posts completely in order to construct the curb blockouts. If end posts extend towards the outside of the bridge, it may not be necessary to remove the end posts.

The end treatment for the 36-inch blockout will require a maximum 6:1 slope to transition down to a maximum 32-inch end height near the guardrail attachment. A 32-inch blockout does not require a reduced height for the end treatment. The preferred end treatment will include a gradual width transition that approximates a 10:1 slope. A block inset for the guardrail attachment should be avoided.

751.1.3.4.jpg


Common Bridge Barrier and Railing (for Rehabilitations)

Type Section
(Test Level)
Allowed Wearing Surface Required Retrofit Notes
Curb and Parapet
(Brush Curb ≤ 6”)
751.1.3.3 less than 6 in..jpg
751.1.3.4 less than 6 section.jpg
(N/A)
3/8” Thin Wearing Surface Use in place with curb blockout for wearing surfaces greater than 3/8” from original deck surface (1)
Curb and Parapet
( Brush Curb > 6”)
751.1.3.3 more than 6 in..jpg
751.1.3.4 more than 6 section.jpg
(N/A)
None without retrofit Use in place with curb blockout (preferred) or thrie beam railing. (1)
Horizontal step must be 6” or less to be UIP.
Brush Curb with Steel Rail
751.1.3.3 street rail.jpg
751.1.3.4 brush section.jpg
(N/A)
None without retrofit Use in place with added curb blockout (preferred) or thrie beam railing. (1)
A variety of steel railing systems were employed on brush curbs. None are acceptable without retrofit.
Thrie Beam
751.1.3.4 thrie beam.jpg
751.1.3.4 thrie beam section.jpg
(NCHRP 350 TL-3)
21” (Min.) from centerline of thrie beam to top of wearing surface Use in place if minimum height to centerline of thrie beam is acceptable. (2) and (4)
May be embedded or bolted thru.
W6x15 blockout is included for all new construction.
Non-blocked railing may be used-in-place when no approach guardrail is provided.
Type A Barrier
(Photo not available)
751.1.3.4 Type A.jpg
(MASH TL-3)
Up to 2” Use in place. (1)
Type B Barrier
751.1.3.3 safety barrier.jpg
751.1.3.4 type b section.jpg
(MASH TL-3)
Up to 2” Use in place. (1)
Type C Barrier
(Photo not available)
751.1.3.4 Type C.jpg
(MASH 2016 TL-4)
Up to 6” Use in place. (3)
Wearing surfaces greater than 3” require a bridge rating analysis
Type D Barrier
751.1.3.4 type d.jpg
751.1.3.4 type d section.jpg
(MASH 2016 TL-4)
Up to 6” Use in place. (3)
Wearing surfaces greater than 3” require a bridge rating analysis
Type G Barrier
(Photo not available)
751.1.3.4 Type G.jpg
(MASH 2016 TL-3)
Up to 2” Use in place. (3)
Use if Type C is considered impractical.
Type H Barrier 751.1.3.4 type h section.jpg
(MASH 2016 TL-3)
Up to 2” Use in place. (3)
Use if Type D is considered impractical.
Steel Two Tube Rail
751.1.3.3 steel two tube.jpg
751.1.3.4 steel 2 section.jpg
(NCHRP 350 TL-4)
Up to 2” Use in place. (3) and (4)
A 42” two tube rail has been successfully crash tested for TL-4, but an end treatment has not been approved for use.
12” x 29” Vertical Barrier
751.1.3.4 vertical.jpg
751.1.3.4 vertical section.jpg
(NCHRP 350 TL-4)
Up to 2” End of barrier modification for new guardrail attachment. (1)
(1) Shall not be used for redecks, widenings, and railing or cantilever full length replacements.
(2) Typically specified for redecks, and railing or cantilever full length replacements. Shall not be used for widenings.
(3) Typically specified for redecks, widenings, and railing or cantilever full length replacements.
(4) Shall not be used on major routes with design speeds greater than 45 mph or on minor and low volume routes with design speeds greater than 55 mph or AADT ≥ 1700. May be used for all other major, minor, and low volume routes.

Aluminum handrail is not crashworthy and does not contribute to barrier height. Use only the concrete portion.

Many other, less common, barrier and railing systems have been constructed. Most are not crashworthy for rural highway speeds. Generally, the replacement of the existing barrier or railing is the only means to upgrade.

For additional information on curb blockouts, see Guidelines for Curb Blockouts.

751.1.3.3 curb and parapet.jpg 751.1 Prelim Design Acceptable Rail No. 4.jpg

A curb blockout is utilized along full length of the curb. Bridge Division provides plans for curb blockouts.

751.1.3.5 Deck Repairs

The project scope is developed from a thoroughly developed structural rehabilitation checklist which includes the typical repairs covered in Sec 704.

Typical Repair

Cleaning and epoxy coating of the bottom and edges of the superstructure is preferred over slab edge repair and unformed superstructure repair because of the relative short life of these repair especially when over traffic. However, consult with Structural Project Manager or the Structural Liaison Engineer for urban regions where repairing the overhang may be preferred. If requested by the core team for aesthetics with extensive patchwork of repairs visible to public, specify on the Bridge Memorandum to apply tinted sealer to slab edge repair and unformed superstructure repair to blend repair to existing concrete.

Non-Typical Repair

Modified deck repair is specified instead of half-sole deck repair on existing poor bridge decks to obtain a little more service life until it is practical to replace the bridge deck, superstructure or entire bridge.

On rare occasions shallow deck repair is used in combination with half-sole deck repair as a cost savings measure on major bridges. Consult with the structural project manager or the structural liaison engineer prior to specifying shallow deck repair.

751.1.3.6 Deck Treatment

The Bridge Wearing Surface Flowchart has been developed to aid in the selection of the appropriate deck treatment.

When possible, multiple types of wearing surfaces should be allowed by specifying on the Bridge Memorandum the appropriate optional wearing surface. It shall also be specified if any of the wearing surfaces of the optional wearing surfaces are not allowed. The specific wearing surface shall be specified on the Bridge Memorandum when only one wearing surface option is allowed.

Concrete Crack Filler

Concrete crack filler in accordance with Sec 704 is typically used for bridges with deck ratings of 7, 8 or 9 with cracks 1/128 inch or less. May also be an option for bridges with deck ratings of 7, 8 or 9 with cracks greater than 1/128 inch and the deck fails a required pull off test.

Concrete Wearing Surface

A concrete wearing surface in accordance with Sec 505 is the preferred deck treatment for bridges with deck ratings of 5 or 6 so long as the barrier height does not become substandard and the bridge remains not posted (or if already posted not be reduced).

Typically, the wearing surface thickness that has the least impact on existing grade is specified on the Bridge Memorandum as the minimum required thickness. When this thickness equals the minimum allowable thickness, as shown below, consider adding 1/2 inch to the minimum required thickness specified on the Bridge Memorandum for hydro demolition projects to provide coverage over existing aggregate protruding into the new wearing surface. For bridges with special repair zones where two different minimum hydro demolitions depths are specified, then two corresponding minimum required thicknesses shall be specified on the Bridge Memorandum.

Wearing Surface Type Allowable Thickness
Latex Modified 1¾″ to 3″
Silica Fume 1¾″ to 3″
Latex Modified Very Early Strength 1¾″ to 3″
CSA Cement Very Early Strength 1¾″ to 3″
Steel Fiber Reinforced 3″ to 4″
Low Slump 2¼″ to 3″
Polyester Polymer ¾″ to 3″

For a deck without an existing wearing surface, scarification of the deck producing a very rough texture in accordance with Sec 216.20 is required to produce a bondable surface for the new concrete wearing surface. Typically, 1/2 inch of scarification is specified on the Bridge Memorandum. Scarification equipment may not engage the deck when less than 1/2 inch of scarification is specified.

For a deck with an existing wearing surface, removing the existing wearing surface plus an additional amount of existing deck in accordance with Sec 216.30 is required to produce a very rough bondable surface for the new concrete wearing surface. Typically, 1/2 inch of additional existing deck is specified on the Bridge Memorandum. Removal equipment may not remove the entire existing wearing surface when less than 1/2 inch of additional deck is specified.

When the estimated deck repair is more than 30 percent of the deck, one inch shall be specified for scarification or for the additional amount of existing deck with the removal of an existing wearing surface. Verify there will be a minimum of 1/2 inch of concrete above the top bars after scarification or after the removal of the existing wearing surface and if necessary, reduce one-inch depth accordingly.

Total surface hydro demolition in accordance with Sec 216.110 performed after scarification or after the removal of the existing wearing surface is preferred for the establishment of a highly rough and bondable surface. For typical bridges, a minimum 1/2 inch of hydro demolition is specified on the Bridge Memorandum. For bridges with special repair zones, typically a 1/4-inch minimum is specified inside special repair zones to avoid deeper penetration into newly repaired areas and a 1/2-inch minimum is specified outside the special repair zones.

Removal of existing deck repair in accordance with Sec 216.110 is required prior to hydro demolition. The estimated quantities for these removals shall include all previous conventional deck repairs, regardless of condition except that for bridges with special repair zones, the removal of all sound and unsound existing deck repairs inside special repair zones shall be included in the estimated quantities for half-sole repair.

Polymer Wearing Surface

A polymer wearing surface in accordance with Sec 623 may only be used if the deck passes a required pull off test. Polymer is typically used for bridges with deck ratings of 7, 8 or 9 with cracks greater than 1/128 inch.The polymer may also be an option for bridges with deck ratings of 5 or 6 that have load rating issues.

Polymer Options
1/4″ Epoxy Polymer
3/8″ MMA Polymer Slurry

If requested by the core team, a black beauty type aggregate shall be specified on the Bridge Memorandum for MMA polymer slurry wearing surface.

If requested by the core team, a high friction (HFST) aggregate shall be specified on the Bridge Memorandum for MMA polymer slurry wearing surface pending a safety benefit/cost ratio analysis performed by district traffic staff. See Roadway non-standard special provision NJSP1513 to reference aggregate requirements and surface friction test.

If requested by the core team, preparation of reflective deck cracks shall be specified on the Bridge Memorandum if during the scoping process there is concern of primer loss with reflective deck crack size at the precast panel joints.

Asphalt Wearing Surface or Seal Coat

Asphalt wearing surfaces in accordance with Sec 403, ultrathin asphalt wearing surfaces in accordance with Sec 413 and seal coats in accordance with Sec 409 are typically used on existing poor bridge decks to obtain a little more service life until it is practical to replace the bridge deck, superstructure or entire bridge.

Grade B1 seal coat aggregate shall be used whenever a bridge deck is to receive an asphalt wearing surface.

Grade A1 seal coat aggregate shall be used whenever the seal coat is to be the final riding surface. Grade C seal coats are no longer used for bridge applications because of dust issues.

751.1.3.7 Bridge Approach Slabs

Follow guidance for new bridges and see EPG 503 Bridge Approach Slabs.

751.1.3.8 Bridge End Drainage

Follow guidance for new bridges and see EPG 503 Bridge Approach Slabs.

751.1.3.9 Environmental Considerations: Asbestos and Lead

Check TMS1 to see if an asbestos and lead inspection has been performed for a structure and include the applicable note shown immediately below on the Bridge Memorandum under the Special Notes Section. The report in TMS will be located in the Images link under the Media tab for the structure. If there is not a report in TMS, contact the Assistant State Bridge Engineer for a report not yet uploaded to TMS. Include the applicable note of the two shown immediately below on the Bridge Memorandum depending on whether an inspection has not been performed or if the inspection report indicates that asbestos or lead, or both are present or not present. (These notes are also applicable for new replacement structures that involve removal of any part of an existing structure.)

“Asbestos and lead inspections have not been performed on this structure (Bridge/Culvert # XXXXX). The Bridge Division will request these inspections and will include the report in the electronic deliverables folder when submitting contract documents to the Design Division for the Letting (Bridge Item).”
“Asbestos and lead inspections have been performed on this structure (Bridge/Culvert # XXXXX). Results indicate that asbestos is present lead is present both are present both are not present. The Bridge Division will include the inspection report in the electronic deliverables folder when submitting contract documents to the Design Division for the Letting (Bridge Item).”

1Available only to MoDOT employees. All others: contact the Bridge Division or the Structural Liaison Engineer directly for information related to EPG 751.1.3.9 Environmental Considerations: Asbestos and Lead.

751.1.4 Retaining Walls

751.1.4.1 Overview

This article is intended to help with the issues unique to retaining walls. Many portions of EPG 751.1.2 Bridges/Boxes will still need to be used when working on retaining walls.


Retaining walls are very much like bridges in that they require the many of the same items, such as:

  • Bridge Survey
  • Bridge Number
  • Bridge Memorandum
  • Soundings
  • Design Layout Sheet

751.1.4.2 Types of Walls

There are two general types of retaining walls used by MoDOT; cast-in-place (CIP) concrete walls and mechanically stabilized earth (MSE) walls. MSE walls are the preferred type due to their lower cost; however, there are several times when MSE walls cannot be used. These include:

  • When barrier or railing must be attached to the top of the wall.
  • When the underlying soil cannot support the weight of the fill and wall (must use CIP on piling).
  • When you don’t have adequate room behind the wall for the reinforcing straps.

In general a minimum reinforcement length of 8.0 ft., regardless of wall height, has been recommended based on historical practice, primarily due to size limitations of conventional spreading and compaction equipment. Shorter minimum reinforcement lengths, on the order of 6.0 ft., but no less than 70 percent of the wall height, can be considered if smaller compaction equipment is used, facing panel alignment can be maintained, and minimum requirements for wall external stability are met.

The requirement for uniform reinforcement length equal to 70 percent of the structure height has no theoretical justification, but has been the basis of many successful designs to-date. Parametric studies considering minimum acceptable soil strengths have shown that structure dimensions satisfying all of the requirements of Article 11.10.5 require length to height ratios varying from 0.8H for low structures, i.e. 10.0 ft., to 0.63 H for high structures, i.e. 40.0 ft.

Significant shortening of the reinforcement elements below the minimum recommended ratio of 0.7H may only be considered when accurate, site specific determinations of the strength of the unreinforced fill and the foundation soil have been made. Christopher et al. (1990) presents results which strongly suggest that shorter reinforcing length to height ratios, i.e. 0.5 H to 0.6 H, substantially increase horizontal deformations.

The reinforcement length shall be uniform throughout the entire height of the wall, unless substantiating evidence is presented to indicate that variation in length is satisfactory.
A nonuniform reinforcement length may be considered under the following circumstances:
Lengthening of uppermost reinforcement layers to beyond 0.7H to meet pullout requirements or to address seismic or impact loads.
Lengthening of the lowermost reinforcement layers beyond 0.7H to meet overall (global) stability requirements based on the results of a detailed global stability analysis.
Shortening of bottom reinforcement layers to less than 0.7H to minimize excavation requirements, provided the wall is bearing on rock or very competent foundation soil.

For walls on rock or very competent foundation soil, e.i., SPT > 50, the Bottom reinforcements may be shortened to a minimum of 0.4H with the Upper reinforcements lengthened to compensate for external stability issues in lieu of removing rock or competent soil for construction. Design Guidelines for this case are provided in FHWA Publications No. FHWA-NHI-00-043 (Elias et al. 2001).

For conditions of marginal stability, consideration must be given to ground improvement techniques to improve foundation stability, or to lengthening of reinforcement.

MSE walls are pre-qualified and listed on the internet in two categories:

  • Small block walls
  • Large block walls

Small block walls are battered walls with a maximum height of 10 feet.

Large block walls are vertical walls with heights that may exceed 10 feet.

Combination wall systems are considered small block wall system and shall be battered with a maximum height of 10 feet.

Aesthetic enhancements may be used for either CIP or MSE walls. If aesthetic enhancements are required by the district, form liners and concrete stains are encouraged rather than actual brickwork and stonework since form liners and concrete stains typically need less maintenance, less loading, less detailing, no extra support ledge and produce no risk of delaminations or falling work. However, for MSE large block walls only, form liners are required for all panels. For additional information, see EPG 751.24.2 Mechanically Stabilized Earth (MSE) Walls.

Any deviation from the criteria listed shall be discussed with Structural Project Manager.

751.1.4.3 MSE Walls

Generally, both the horizontal alignment and the top of wall elevations are supplied by the district in the Bridge Survey. You do need to check the top of wall elevations to make sure the district accounted for any concrete gutters placed behind the top of the wall (Gutters are necessary if the slope of the fill can direct water towards the top of the wall, i.e. positive sloping and flat backfills). The district should decide whether to use Type A or Type B gutters (Standard Plan 609.00), or Modified Type A or Modified Type B gutters (Standard Plan 607.11) if fencing is required, and where they should drain (to be shown on roadway plans). For general guidelines, see EPG 751.24.2 Mechanically Stabilized Earth (MSE) Walls.

You will also need to set the elevations for the top of the leveling pad. The minimum embedment, which is the distance between the finished ground line and the top of the leveling pad, is based on this table: (FHWA Demonstration Project 82)

Slope in Front of Wall Minimum Embedment
Horizontal H/20
3H:1V H/10
2H:1V H/7

The absolute minimum embedment is 2 ft. When the soundings are returned, they will include a minimum embedment necessary for global stability.

Preliminary cost estimating MSE walls is based on the unit price bid history and on the square footage of the area of the face of the wall. The unit price per square foot of wall includes wall elements, leveling pad and backfill. Excavation and retained fill are not included.

If soundings indicate weak material exist, then the designer should investigate that sufficient right of way limits exist to address the required length for the soil reinforcement.

For additional information, see EPG 751.24.2 Mechanically Stabilized Earth (MSE) Walls.

751.1.4.4 CIP Concrete Walls

Once you determine that you must use a CIP wall, there is very little to do as far as the layout of the structure. Both the horizontal alignment and the top of wall elevations are supplied by the district in the Bridge Survey. You do need to check the top of wall elevations to make sure the district accounted for any concrete gutters placed behind the top of the wall. These are necessary if the slope of the fill will direct water towards the top of the wall. The district should decide whether to use Type A or Type B gutters (Standard Plan 609.00), or Modified Type A or Modified Type B gutters (Standard Plan 607.11) if fencing is required, and where they should drain to.

You will also need to set the elevations for the top of the footing, which should be a minimum of 2 feet below the finished ground line for walls south of Interstate 70 and 3 feet below the finished ground line for walls north of Interstate 70. In tight roadway situations where a barrier or railing is to be placed on top of the wall, make sure that a stem thickness of 16 inches will fit.

Check with the district contact to determine if they want any coping on the exposed face of the wall.

French drains will be used to relieve water pressure behind the CIP wall as a default. If you expect to encounter springs or swampy conditions, then check with the district contact on calling for an underdrain. If the decision is made to use an underdrain, the porous backfill and pipes are Roadway Items and this must be noted on the Bridge Memorandum and Design Layout.

For details on requesting soundings, see EPG 751.1.2.20 Soundings (Borings).

If you have indications that the foundation material is very poor in quality (less than 1 ton per sq. ft. allowable bearing), consider piling and include in the Preliminary Cost Estimate. Preliminary cost estimating should follow EPG 751.1.2.18 Preliminary Cost Estimate and be based upon unit price bid history. More refined cost estimating should follow cost-basing estimating.

751.1.4.5 Obstructions

Any time the retaining wall will encounter obstructions, provisions must be made on the final plans. Therefore, if you are aware of any obstructions, they should be called out on the Bridge Memorandum and Design Layout Sheet. Here are some examples of types of obstructions and how to describe them on the layout:


Type of Obstruction Description
Lighting Foundation Std. 45’ Light Pole, Sta. 167+48.50,
  16 ft. left
Sign Truss Foundation Truss T-72, Sta. 172+41.80,
  31 ft. right
Drop Inlet 2’ x 2’ Type D Drop Inlet,
  Sta. 163+12.45, 14 ft. left