748.7 Bridge Reports and Layouts
From Engineering Policy Guide
|Form BR 105R (Bridge Survey Report)|
|Form 105 Sl (Example Bridge Profile)|
|Form 105 S2 (Example Stream Crossing Plan)|
|Sturctural Rehabilitation Checklist|
|MSE wall sample plans|
|Request for Final Soundings of Structure|
Bridge surveys prepared and submitted to the Bridge Division by the district provide the basis for preliminary bridge layouts and ultimately for the preparation of bridge plans by the Bridge Division. Care exercised during the gathering and preparation of bridge survey data will be reflected throughout the life of the proposed bridge. The hydraulic design of the bridge waterway opening for a stream crossing is almost entirely based upon bridge survey data gathered in the field or from aerial photographs. Bridge surveys for grade separations should accurately describe geometrics, grades and other pertinent features of the proposed improvement. When new grade separation structures are to be incorporated with existing facilities or when existing structures are to be widened or rehabilitated, the bridge survey should reflect geometrics and grades of existing facilities as they exist. Seldom are existing geometrics and grades the same as shown on original design plans.
Bridge survey data should include all information regarding the bridge site which will have a bearing on the bridge layout and design.
Consulting engineering firms retained by the department to prepare bridge layouts should contact the Bridge Division for additional requirements beyond those listed in this article.
7188.8.131.52 Bridge Survey Forms
Bridge survey data is submitted on standard forms (Forms BR 105 R, 105 Sl and 105 S2) to the Bridge Division. These forms are available in Word and Microstation.
7184.108.40.206 Bridge Memorandum
Upon receipt of the bridge survey, the Bridge Division will review the bridge survey data and make an in-depth analysis of the proposed crossing. The analysis will include hydraulic design of the waterway opening for stream crossings, geometric layout for grade separations, economic analysis of structure types and span lengths and investigation of any special features evident from the bridge survey data. A tentative bridge layout will be prepared.
A bridge memorandum will be prepared on the standard form covering the details of the proposed bridge. Three copies of the bridge memorandum are sent to the district for review and signature. The district retains one signed copy of the bridge memorandum and returns the remaining signed copies to the Bridge Division for distribution and filing.
The bridge memorandum is the instrument which coordinates bridge plan and roadway plan preparation. If, during the design process, revisions 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 and noted on all copies of the memorandum.
7220.127.116.11 Bridge Permits or Approvals by Other Agencies
- Bridge Layout Approval by Organized Drainage District: Written agreement documenting drainage district approval of the proposed structure layout is to be obtained by the district.
- Railroad Approval of Preliminary Bridge Layout and of Final Bridge Plans: Written approval from the railroad of proposed structure and of design plans is obtained by the Multimodal Operations Division with the cooperation of the Bridge Division.
- U.S. Corps of Engineers Sec. 404 Permit: Application is initiated by the district, submitted to and further pursued by the Design Division with the cooperation of the Bridge Division.
- U.S. Coast Guard Bridge Permit: When required, application is prepared and submitted by the Bridge Division.
- Utility Relocations or Permits: Agreements are obtained by the district with cooperation, if necessary, of the Design Division and the Bridge Division.
- FHWA Bridge Approvals: When FHWA preliminary bridge layout approval or bridge plan approval is required, written approval is obtained by the Bridge Division.
- Flood Plain Development Permit: The GHQ Bridge will prepare and submit the application to the State Emergency Management Agency.
- FHWA, Missouri State Historic Preservation Officer (SHPO), Advisory Council on Historic Preservation (ACHP): Disposition of historically significant bridge to be replaced must be determined. This disposition will be coordinated by the Preliminary Studies Division. Preservation of the historic bridge in place (rehabilitated or for alternative uses such as pedestrian walkway) must be considered.
748.7.3 Preparation of Bridge Survey Report
A proper procedure for, and a methodical approach to the analysis and computations for preparation of a bridge survey report will result in a realistic recommendation for the proposed structure. For stream crossings, the district design personnel are to determine the drainage area and valley slope at the bridge site from available maps as outlined in Hydrologic Analysis.
Formulas upon which hydraulic calculations are based are approximations which have been developed from model studies, stream gaging and/or statistical analysis. The hydraulic design formulas therefore are considered to be approximations. Due to the diverse nature of individual drainage basins, considerable engineering judgment must be exercised in hydraulic design to obtain reasonable and practical results. Measurements and calculations are made to the accuracy tabulated in the Table "Accuracy for Bridge Survey Measurements and Calculations."
For grade separation bridge surveys and structure recommendations, a higher degree of accuracy is possible and necessary. A thorough analysis of the geometric and survey data for grade separation layouts will lead to realistic structure recommendations and will substantiate the adequacy of the bridge survey data to be submitted to the Bridge Division.
|Less than 10 mi2||0.1 mi2|
|Greater than 10 mi2||1.0 mi2|
|Less than 2000 ft3/s||10 ft3/s|
|Greater than 2000 ft3/s||100 ft3/s|
|Area (each increment)||1 %|
|Wetted Perimeter (each increment)||1.0 unit|
|Water Surface Elevation|
|Design High Water Elevation||0.1 ft.|
718.104.22.168 Design Flood Frequency
For the design flood frequency to be used for the hydraulic design of bridge openings see Hydraulics and Drainage.
The basic flood frequency is, by definition, the 100 year frequency. All bridge plans must show the estimated discharge, calculated highwater elevation and estimated backwater for the basic flood.
722.214.171.124 Estimating Flood Discharges
Numerous USGS recording stream gages have been maintained for many years on selected Missouri streams. For bridge sites at or near one of these gages, the gage data is used in estimating discharge. When sufficient years of data have been collected at a stream gage, the data may be statistically analyzed to estimate discharge for the selected design flood frequency. Gage data is analyzed by the Log-Pearson type III method. A computer program for the analysis is available and, on request, the Bridge Division will perform the analysis and provide discharge estimates to the district.
For bridges without nearby USGS stream gages, the methods of estimating discharge given in Hydrologic Analysis are used.
7126.96.36.199 Required Freeboard
The required structure grade elevation is obtained by adding freeboard and superstructure depth to the design highwater elevation. Freeboard is defined as the vertical distance between the design highwater elevation and the lower limit of the superstructure. See Hydraulics and Drainage.
7188.8.131.52 Bridge Skew
Bridge skew increases bridge cost and should be avoided whenever possible. For stream crossings, skew angles of less than 10 degrees are not usually used. For grade separation structures, skew should be minimized. For grade separations small skew angles are frequently required where a right angle intersection between the two intersecting facilities is not possible.
The bridge survey data includes recommended grades across and adjacent to the structure. If the grades in the vicinity of the structure are to provide balanced grading quantities, the grade and grading quantities are analyzed prior to submitting the bridge survey report to the extent necessary to assure that excessive grade changes will not be necessary. The approximate depths of various structure types are shown on Superstructure Depth Requirements. The data on this figure, along with the required freeboard or minimum vertical clearances for grade separations are used to establish the minimum elevation of the grade across the structure.
Bridge widths from face to face of curbs are obtained from Bridge Width.
7184.108.40.206 Preparation of Bridge Survey Report
7220.127.116.11.1 Form BR 105R (Bridge Survey Report)
Applicable portions of this form are filled in completely by the district.
- Page 1. The location of the road is described from points which can be readily identified on maps, such as towns or other state routes. The anticipated means of handling traffic, such as a temporary bridge, is provided. Data for existing bridge is completed if existing bridge is on or near alignment of proposed bridge. All lines under high water elevations at proposed bridge site are completed. The high water elevation at the survey centerline is the proper elevation to show.
- Page 2. Information on any improvements near the proposed bridge is provided. Such improvements may include, but are not limited to, residences, businesses, other buildings and crop fields. The data for existing bridges need be completed only for bridges within 1000 ft. of the proposed bridge except where this data for structures beyond this distance will obviously be of value. The "Additional Remarks" space is used for general information relating to the crossing and is not restricted to remarks relating to existing bridges.
- Page 3. The descriptive answers on this page are used as a basis for the hydraulic analysis of the crossing by the Bridge Division and should be carefully completed by the district. The lower water elevation is the lowest water elevation during a year of normal rainfall. If the crossing is over an organized drainage district ditch, or encroaches on their levees, the data at the bottom of the page is completed.
- Page 4. Photographs depicting the site conditions at the time of survey are provided.
- Page 5. General Instructions for Bridge Surveys.
718.104.22.168.2 Form 105 Sl (Example Bridge Profile)
Profiles are plotted on this form to a preferred scale of 1 in. = 10 ft. (1:100) in each direction. Three lines of ground profiles, plus the proposed profile grade, are placed on the upper half of this sheet. The profiles are positioned so that the profile grade will be located near the top of the form. The area directly below the proposed location of the structure is to be reserved for boring data for structures (See Example Stream Crossing Profile and Example Grade Separation Profile. Dual structures require the use of two forms. If a common profile is used for both dual structures, the common profile is shown on both sheets. The profile grade and finish grade under the structure is plotted on this portion of the form. The lower half of the form is used to show the streambed profile. All three valley sections, both typical channel sections, sections under existing bridges, etc are shown on a separate sheet (See Example Channel Sections). These items should be plotted on a horizontal scale of 1 in. = 100 ft. (1:1000) and a vertical scale of 1 in. = 10 ft. (1:100). More than one form may be used to avoid crowding. The proposed profile grade is shown on the survey centerline profiles. The extreme high water elevation is shown on the centerline profile and each of the valley sections. If actual high water elevations are not obtained for each of the valley sections, the high water elevation from the survey centerline is shown at each valley section; however this elevation is adjusted to account for slope of the stream and the distance to each valley section. The adjustment is made by adding or subtracting, as appropriate, the local streambed slope multiplied by the distance along the streambed profile between the valley section and the survey centerline.
722.214.171.124.3 Form 105 S2 (Stream Crossing Plan)
This form is used to show a plan of the stream crossing, and includes survey alignment, stream meander, topography, contours, location of any known utilities, north point, direction of flow, and datum. This form is completed to a scale of 1 in. = 100 ft. (1:1000). Where the extent of the area is such that the entire area cannot be shown on one form at this scale, a scale of 1 in. = 200 ft. (1:2000) may be used. Additional forms with match lines may be used as required. The stream meander is shown using a solid line for the high bank and a dashed line for any secondary or low bank. The contours are shown using a heavier line at 10 ft. (5 m) intervals. A typical section is shown on this form or Form 105 Sl showing the roadway section at the bridge, including surface width and type, roadbed width, superelevation and widening, and slopes. The typical section is shown schematically without detailing surface and base thicknesses, etc.
7126.96.36.199 Handling Traffic
If provision is to be made for handling traffic in the immediate vicinity of the structure that will affect the structure in any way, a recommendation for the location of bypasses, and temporary provisions for handling drainage are included on the bridge survey report.
7188.8.131.52 Bridge Fencing
Information on Fencing Applications contains information on where and how to specify fencing on bridges.
The completed bridge survey report including cover letter, Form BR 105R and the completed drawings (Forms 105 Sl and 105 S2) are submitted to the Bridge Division Bridge Survey Processor (PDF and the electronic MicroStation files including all attached references, hard copies optional), with a copy of the letter to the Design Division. The Bridge Survey Processor may be contacted by email at Bridge Survey Processor@modot.mo.gov.
748.7.4 Grade Separation Reports
Grade separation reports are prepared on Form 105 Sl and Form 105 S2 by the district. The completed forms are submitted to the Bridge Division by the district similar to the procedure followed on bridge survey reports. A bridge memorandum is prepared by the Bridge Division that is handled in the same manner as the memorandum for other bridge survey reports. Grade separation reports for structures in interchange areas are not submitted until after interchange geometrics are approved.
7184.108.40.206 Grade Separation Layout
Many of the criteria and principles pertaining to the layout of stream crossing bridges are also applicable to grade separation bridges.
Bridge length and substructure locations are usually controlled by horizontal and vertical geometrics. The minimum vertical and horizontal clearances are given in Grades.
For structures spanning freeway type facilities, two-span bridges with semi-deep abutments are used if the required span length does not exceed 135 ft. The centerline of bearing at the abutment is located midway between the toe of the end slope and the intersection of the end slope with the grade line over the bridge.
For highways over railroad grade separations, the minimum bridge length is controlled by a theoretical railroad cross section. The distance from the track centerline (for multiple tracks, the outside track centerline) to the embankment slope at the elevation of the top of rail is 20 ft. This distance may be increased up to 8 ft. on one side of the railroad to allow for a railroad off-track maintenance road. The need for the off-track maintenance road must be justified by the presence of an existing road or the railroad must provide evidence of future need for such a road.
7220.127.116.11 Information Necessary
Form BR 105R is not required for grade separation reports. Forms 105 Sl and 105 S2 for grade separation reports include typical sections for both roads adjacent to the structure, the location of survey centerline and profile grade on the typical sections, and ramp details that will affect the structure, including the location of ramp base line, ramp surface type and width, and roadbed width. The thruway profile is indicated on Form 105 Sl for a distance of at least 500 to 1000 ft. on each side of the proposed intersection. The crossroad profile is indicated on this form for a distance of at least 500 ft. each side of the intersection. Contours are required for Form 105 S2, only where the structure is skewed more than 50 degrees and the natural ground elevation varies more than 10 ft. within the limits of the structure. Where contours are required, they extend to a minimum radial distance of 500 ft. from the intersection. If contours are not required, cross sections are submitted along both roads to beyond the limits of the structure. Other data required on grade separation reports, such as topography and offset profiles, are the same as the requirements for other bridge survey reports. Where the grade separation structure is over an existing pavement or railroad, the grade separation report includes cross sections or profiles along the pavement or railroad to the extent required. Where cross sections are submitted in lieu of profiles, the cross sections show the elevation of the pavement centerline and edges or the elevation of the railroad rails. When skewed grade separations over railroads are involved, an additional profile sheet on Form 105 Sl is to be included with the bridge survey report and preliminary layout. This additional sheet is to show the cross section at right angles to the railroad at the intersection of the centerline of the roadway of the structure and centerline of tracks. If multiple tracks are involved, the centerline of any main line track may be used. In cases of dual structures, separate cross sections are required for each structure. The cross section is to show railroad roadbed, rails, ditches, etc. All of this information is to be plotted within the upper half of the sheet. This sheet will be submitted to the railroad with the bridge layouts instead of the regular Form 105 Sl which shows the three profiles and sections parallel with our centerline. The bridge survey plat sheet (Form 105 S2) is to show a line at right angles to the railroad at the location of the cross sections. The zero or 0+00 (0+000) point of the cross section is to be at or near the railroad right of way line and the direction in which the section is taken clearly shown. For examples of Forms 105 Sl and 105 S2 see:
- Example Grade Separation Profile without Borings (Form 105 S1)
- Example Grade Separation Profile (Form 105 S1)
- Example Grade Separation Profile over Railroad (Form 105 S1)
- Example Skewed Grade Separation Profile over Railroad (Form 105 S1)
- Example Grade Separation Plan (Form 105 S2)
- Example Bridge Survey Plat over Railroad (Form 105 S2)
Grades to the limits of the profiles are included on the report for the thruway and the crossroad. If the grades are to provide balanced grading quantities, the same care as required for bridge survey reports is exercised. Superstructure depth requirements are used along with the Minimum Vertical Clearances Table to establish the relation of the grades at the intersection where minimum clearances control.
The following values are to be used for construction of new structures. Please note that the minimum vertical clearance value of 16 ft. 6 in. used in the first table is based upon the "required" minimum vertical clearance of 16 ft., plus 6 in. to accommodate future resurfacing of the roadway.
|Facility Under Structure||Clearance|
|Interstate and Principal Arterial Routes||16 ft. 6 in. (incl. shoulders)|
|Other State Routes > 1700 vpd||16 ft. 6 in. (incl. shoulders)|
|Other State Routes < 1700 vpd*||15 ft. 6 in. (incl. shoulders)|
|Other Streets and Roads*||14 ft. 6 in. (does not incl. shoulders)|
|Railroads**||23 ft. 0 in.|
|*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 ft. 6 in. A minimum vertical clearance of 15 ft. 6 in. is required for bridges located in commercial zones. A minimum vertical clearance of 17 ft. 6 in. is required for pedestrian overpass facilities.|
|**For minimum clearances during construction, see Standard Details for bridges.|
|Facility Under Structure||Clearance|
|Interstate, Primary and Urban Routes||30 ft.|
|Ramps & Auxiliary Lanes||5 ft. 3 in. from shoulder line|
|Other State Routes||5 ft. 3 in. from shoulder line|
|Other Streets and Roads||5 ft. 3 in. from shoulder line 2 ft. from face of barrier curb|
|Railroads* **||14 ft. 0 in. & 22 ft. 0 ft. (min.)|
|*Measured from centerline of track. The minimum clearance of 22 ft. 0 in. 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. Where narrow median is used, provide 5 ft. 6 in. minimum clearance from edge of traveled lanes to face of columns on median side.|
|**For minimum clearances during construction, see Standard Details for bridges.|
Refer to EPG 131.1.3 Deficient Vertical Clearances on Interstates for information about coordinating minimum vertical clearance for grade separation structures with the Defense Department.
748.7.5 Bridge Rehabilitation and Miscellaneous Structures
Surveys for structures other than normal bridges are frequently required. Depending on the nature of the proposed construction, specialized data may be required in addition to the usual bridge survey data. Pre-survey planning is essential to assure that adequate survey data is obtained for the preparation of accurate structure plans. Seldom are existing elevations and dimensions the same as shown on original structure plans.
718.104.22.168 Bridge Rehabilitation Surveys
Bridge rehabilitation may include widening, redecking, lengthening, repairing or other work necessary to restore an existing bridge to serviceable condition. When bridge rehabilitation of any type is proposed, consideration should be given to total structure rehabilitation. Once the scope of the project is decided, the Structural Rehabilitation Checklist shall be completed and sent to the Bridge Division Bridge Survey Processor along with any additional descriptions and photographs of deteriorated members. This will aid the Bridge Division in recommending repairs and in estimating repair costs. The Bridge Survey Processor may be contacted by email at Bridge Survey Processor@modot.mo.gov.
Significant historical bridges proposed for rehabilitation will need to have the proposed work coordinated with FHWA, SHPO, and ACHP. A Memorandum of Agreement (MOA) executed by MoDOT between these three agencies will be required. The Design Division will coordinate this.
The following guidelines should assist in developing bridge rehabilitation survey reports for bridge widening and bridge deck replacement projects.
722.214.171.124.1 Bridge Widening
- Stationing at bridge ends and at the centerline of each intermediate substructure unit.
- Deck elevations at 10 ft. intervals at the centerline and gutterlines. The centerline elevations may be omitted if high traffic volumes are present and would represent a hazard to survey personnel.
- Substructure bearing beam elevations at each end of each substructure unit.
- Groundline profiles at the centerline of the roadway and right and left at the approximate location of new footings.
- Details of existing geometrics and improvements.
- Profile of existing roadway for 100 ft. ± from each end of the existing bridge.
7126.96.36.199.2 Bridge Deck Replacement
Field survey elevations are not normally needed for bridge redeckings.
7188.8.131.52 Surveys for Miscellaneous Structures
7184.108.40.206.1 Retaining Walls
Surveys for all retaining walls shall be submitted to the Bridge Division Bridge Survey Processor (Bridge Survey Processor@modot.mo.gov) to determine design features. Sufficient geometric and profile information shall be included on the survey sheets to locate the proposed structure in relation to an adjacent roadway, including right of way and/or permanent easement information which might affect the location of the proposed retaining wall. Existing and proposed ground line profiles immediately in front of and behind the proposed retaining wall shall be part of the required survey. Cross-sections taken at 25 ft. ± intervals showing existing and proposed sections and location of the proposed retaining wall with respect to the referenced roadway or right of way shall be included when submitting surveys for a retaining wall to be designed by the Bridge Division.
Plans for mechanically stabilized earth walls will be developed by the districts unless they go under a bridge. Plans for "L" type retaining walls and "cantilever" type retaining walls will be developed by the Bridge Division. For L and cantilever type retaining walls 5 ft. or less in height, the Bridge Division will furnish typical design sections with reinforcing steel and joint details sufficient for development of remaining details by the district. Plans developed by the district shall include all plan views, elevations, sections and quantities similar to a retaining wall designed by the Bridge Division.
When the use of retaining walls along the shoulder line of roadways is required, either in the cut or fill sections, the same type of wall through the entire structure length is preferable rather than incorporating an "L" type at each end when height permits. In fill sections, a concrete safety barrier curb shall be provided and shall be tied into a concrete shoulder as a roadway item. In cut sections, a type B concrete traffic barrier shall be provided as a roadway item and placed against the retaining wall at the shoulder line. Provisions shall be made to attach standard bridge anchor section (thrie beam) to eliminate point obstacles where retaining walls end in cut or fill sections.
"L" Type Retaining Walls. The "L" type takes its name from being shaped like the letter "L." The footing of the wall may be placed under the proposed fill or as part of a paved shoulder and may or may not have a concrete safety barrier curb for traffic safety. Walls greater than 5 ft. in height are to be identified by a bridge number, which can be acquired from the structural resource manager in the Bridge Division.
"Cantilever" Type Retaining Walls. This is a conventional reinforced concrete type wall supported by a spread footing or pile footing. "Cantilever" type walls greater than 5 ft. in height are to be identified by a bridge number which can be acquired from the structural resource manager in the Bridge Division.
Mechanically Stabilized Earth (MSE) Wall Systems. Mechanically stabilized earth wall systems consist of a reinforced soil mass placed behind facing units. Types of MSE walls include small block and large block (panel). Information concerning the types, appropriate uses and design of MSE walls can be found in EPG 751.24 LFD Retaining Walls. Contractors are responsible for performing the design of MSE walls. Only the wall systems shown in the bridge prequalified products listing will be available for use by the contractor. The bridge prequalified products listing is available through the Bridge Division or on MoDOT’s website.
Plans for MSE walls will be developed by the District unless they go under a bridge, in which case the Bridge Division will develop the plans.
The following table provides an overview of MSE wall design procedure:
|Exceptions||The Bridge Division will still be responsible for producing the plans for any MSE walls that go under a bridge or act as wingwalls for a bridge.|
|Plans||District will prepare plans for each wall. (See MSE wall sample plans) The latest notes can be found in EPG 751.50 Standard Detailing Notes. That article should be checked often to ensure you are using the most up-to-date notes.|
|Wall Nos.||District will assign each wall a number using a system devised by the Bridge Division (Dx-000x). Each District will need to keep a log of the wall nos. used. This log should include the beginning station and job no. for each wall no. assigned.|
|Soundings/Borings||District will submit the Request for Final Soundings of Structure for each wall to the Geotechnical Director in Central Office. The District Geologist should be copied on this request.|
|Excavation Behind the Wall||The excavation behind the walls will continue to be included in the Roadway excavation quantities.|
|Special Provisions||A special provision is no longer required for MSE walls. The information needed is in Sec 720 of the Standard Specifications.|
|Pay Items||MSE walls only have one pay item: 720-10.00 Mechanically Stabilized Earth Wall Systems. This is bid per square foot and will now be a Roadway Item when the districts do the plans and a Bridge Item when the Bridge Division does the plans.|
|Shop Drawings||Do NOT send to the Bridge Division. They will be signed and sealed by a Missouri PE and the Resident Engineer will handle them like other shop drawings that aren't submitted to Central Office.|
|Approved Systems||The Bridge Division will continue to be responsible for reviewing and approving systems from manufacturers.|
|Historical Plans||The MSE wall plans will be part of the roadway plans so they will be scanned and saved in the same manner.|
|Help||Contact the Bridge Division|
When NOT to Use MSE Walls - You must have adequate room behind the wall for the reinforcing straps (need horizontal clearance behind the wall of approximately 0.7 times the height). You also can NOT use MSE walls in locations where the underlying soil cannot support the weight of the fill and the wall. This is determined by the District Geologist/Geotechnical Director (rare occurrence).
Minimum Embedment - Minimum embedment is defined as the distance between the finished ground line and the top of the leveling pad. It is based on this table (FHWA Demo. #82):
|Slope in Front of Wall||Minimum Embedment|
The absolute minimum embedment is 2 ft. When the soundings are returned from the Geotechnical Director, they will include a minimum embedment necessary for global stability.
7220.127.116.11.2 Other Miscellaneous Structures
Elevations and geometric data sufficient to develop plans for the proposed structure, including special footings such as for high mast tower lights, should be provided. Any subsurface investigation required will be coordinated by the Bridge Division. Right of way and/or permanent easement limits expected to affect the location or dimensions of the structure should be provided.
718.104.22.168.3 Guidelines for the Design of Miscellaneous Foundations
Examples of miscellaneous foundations, other than bridges, requiring geotechnical surveys and specific design are sign trusses, high mast lighting, etc. The district should submit the following information to the Bridge Division Bridge Survey Processor (Bridge Survey Processor@modot.mo.gov) when a foundation design is required. Providing this information as outlined below, and in a timely manner, will allow the Bridge Division to produce cost-efficient designs and details for structural foundations.
Foundation designs for tubular span supported highway signs will be designed as shown in the standard plans. Foundation designs for box trusses (i.e., aluminum, butterfly and cantilever, and structural steel) will be determined by the Bridge Division relative to cost-effectiveness.
The Bridge Division personnel will be available to serve as a liaison between the district and involved functional units.
Time Period. The Bridge Division will need 22 weeks to design any miscellaneous structure foundations and it is essential that all required information be submitted no later than 22 weeks prior to the due date. Within this 22 week timeframe, the Soils and Geology Section will need 10-12 weeks to perform the following:
- Put the geotechnical survey into the drilling schedule.
- Allow time for inclement weather conditions.
- Drill and sample the foundation materials.
- Perform strength and classification tests on the soil and rock encountered in the drilling operations.
- Interpret the geotechnical data and report findings and recommendations for the foundation design.
District Request. Unless a drilled shaft foundation is specifically requested by the district to be the only option considered, the Bridge Division will choose the most cost-efficient foundation (spread footing or drilled shaft foundation). Value engineering proposals, after award of the project, for the foundation design will not be considered and will be stated as such in the Bridge special provisions.
Layout. The district is to provide stationing and offsets for foundation locations to the Bridge Division so that the miscellaneous foundation layouts can be sent to the Construction and Materials Division with other structure layouts from the Bridge Division. This procedure allows for surveying, utility marking and dispatching of drilling equipment and personnel in the most efficient manner.
Geotechnical Report to the Bridge Division. The Construction and Materials Division will provide geotechnical parameters for design of the foundations to the Bridge Division Bridge Survey Processor (Bridge Survey Processor@modot.mo.gov), with a copy to the district.
Location and Sign Information Layout. The district will provide detailed information about each structure. The information typically shown on the data sheet and the cross section for each structure in a set of roadway plans is necessary for the proposed foundation design computations. The quantity for footing and pedestal concrete, normally shown on the D-32, D-33 and D-34 truss data sheets, is not required with this submittal.
Bridge Division Design Information Submittal. The district will receive foundation details, quantities and a cost estimate from the Bridge Division to incorporate into the final project design.