751.35 Concrete Pile Cap Integral End Bents

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751.35.1 General

751.35.1.1 Material Properties

Concrete
Class B Concrete (Substructure) \, f'_c = 3.0 ksi
  \, n = 10

Class B-1 Concrete (Substructure) may also be used in special cases (See Project Manager). The following equations shall apply to both concrete classes:


Concrete modulus of elasticity, \, E_c = 33000 K_1 w_c \sqrt [1.5]{f'_c}
Where:
\, w_c = unit weight of non-reinforced concrete = 0.145 kcf
\, K_1 = correction factor for source of aggregate = 1.0
Modulus of rupture: For minimum reinforcement, \, f_r = 0.37 \sqrt{f'_c}
  For all other calculations, \, f_r = 0.24 \sqrt{f'_c}
\, \sqrt{f'_c}  is in units of ksi    


Reinforcing Steel
Minimum yield strength, \, f_y = 60.0 ksi
Steel modulus of elasticity, \, E_s = 29000 ksi

751.35.2 Design

751.35.2.1 Limit States and Factors

In general, each component shall satisfy the following equation:

\, Q = \sum \eta_i \gamma_i Q_i \le \phi R_n = R_r

Where:

\, Q = Total factored force effect
\, Q_i = Force effect
\, \eta_i = Load modifier
\, \gamma_i = Load factor
\, \phi = Resistance factor
\, R_n = Nominal resistance
\, R_r = Factored resistance


Limit States

The following limit states shall be considered for abutment design:

STRENGTH – I
STRENGTH – III
STRENGTH – IV
STRENGTH – V
SERVICE – I
FATIGUE
EXTREME EVENT - II

See LRFD Table 3.4.1-1 and LRFD 3.4.2 for Loads and Load Factors applied at each given limit state.


Resistance factors

STRENGTH limit states, see LRFD 5.5.4.2 and LRFD 6.5.4.2
For all other limit states, \, \phi = 1.00


Load Modifiers

751.35.2.2 Loads

Dead Loads

Loads from stringers, girders, etc. shall be applied as concentrated loads applied at the centerline of bearing. Loads from concrete slab spans shall be applied as uniformly distributed loads.


Live Loads

Loads from stringers, girders, etc. shall be applied as concentrated loads applied at the centerline of bearing. Dynamic load allowance (impact) should be included for the design of the beam. No dynamic load allowance should be included for foundation design.

For wings with detached wing walls, no portion of the bridge live load shall be distributed to the detached wall. The detached wing wall shall be designed as a retaining wall. The weight of the safety barrier curb on top of the wall shall be included in the dead load.


Collision

Collision shall be designed if abutments are located within a distance of 30.0 feet to the edge of roadway, or within a distance of 50.0 feet to the centerline of a railway track and conditions do not qualify for exemptions given in EPG 751.2.2.5.

751.35.2.3 General Design Assumptions

Beam

The beam shall be assumed continuous over supports at centerline of piles.

One half of the dead load of the approach slab shall be included in the beam design.


Wing

The standard horizontal reinforcement shown below was designed for soil pressure, EH, live load surcharge, LS and a railing collision force, CT for Extreme Limit State II Load Combination.


751.35 general design assumptions-pressure diagram for wing.gif


The minimum steel placed horizontally in wings shall be as shown in the figure below.


751.35 general design assumptions-part section thru beam.gif
Part Section Thru Beam

751.35.2.4 End Bent Analysis

The following steps shall be used to design integral end bents.


Step 1 – Obtain loads from superstructure

The live load reactions (LL), dead load of structural components (DC), and dead load of future wearing surface (DW) will be needed to design the end bents. Strength I Load Combination will be used to design the reinforcement.


Step 2 – Design bearing pads or girder chairs

From the loads obtained in Step 1, design the bearing pads or girder chairs according to EPG 751.11.


Step 3 – Find beam cap width

The standard beam cap width will be 3’-0”. However, if the bearing pad size required exceeds the allowable edge distance, the beam cap width may be widened. The bearing pads shall be centered over the centerline of pile location, which is 15” away from the stream or crossing face of the cap.


Step 4 – Design longitudinal steel in beam cap

If the centerline of bearing is 12” or less on the centerline of piles, use 4 - #6 bars at the top and bottom of the beam cap. Otherwise, the ultimate moment used for designing the longitudinal steel shall be approximated by the following equation and figure. The loads shall be factored according to the Strength I Load Combination.

\, M_u = 0.2 R_u L + 0.13 WL^2

Where:

\, R_u = maximum interior girder reaction of factored superstructure loads, kips.
\, L = pile spacing, ft.
\, W = factored substructure loads equally distributed across the beam, k/ft.


751.35 basic assumption for beam analysis.gif

Basic Assumption for Beam Analysis


A minimum of 4 - #6 Bars shall be used for the longitudinal steel in the beam cap. If more steel is required, increase bar size and keep the number of bars to 4. For example, use 4 - #7 bars instead of 5 - #6 bars.

The minimum reinforcement and bar spacing shall also be checked against the appropriate limits.


Step 5 – Design for number and size of pile

751.35.2.5 Beam Reinforcement Special Cases

SPECIAL CASE I

If centerline bearing is 12" or less on either side of centerline piles, for all piles (as shown below), use 4-#6 top and bottom and #4 at 12" cts. (stirrups), regardless of pile size.

751.35 beam reinforcement special case 1.gif


SPECIAL CASE II

When beam reinforcement is to be designed assuming piles to take equal force, design for negative moment in the beam over the interior piles.

751.35 beam reinforcement special case 2.gif
(*) Dimensions are for illustration purposes only.

751.35.3 Dimensions

751.35.3.1 Front Sheet

Notes: The following are details and dimensions for the Plan view on the Front Sheets.
  Details for unsymmetrical roadways will require dimensions tying Centerline Lane to Centerline Structure.


751.35 front sheet-plan of end bent.gif

751.35.3.2 Wing Brace

The wing brace dimensions will only vary on the wing with obtuse angle. Wing brace dimensions shown are minimum dimensions. The wing brace with the acute angle will always be 18" minimum.

751.35 wing brace details-skews 0 thru 45.gif
Skews 0° thru 45°
 
751.35 wing brace details-skews 45 thru 55.gif
Skews 45°00'01" thru 55°
 
751.35 wing brace details-skews 55 and over.gif
Skews 55°00'01" and Over
Note: Left advance shown, right advance similar.

751.35.3.3 Prestressed Girder End Bent

751.35 prestressed girder end bent-section near wing.gif 751.35 prestressed girder end bent-section a-a.gif
Section Near Wing Section A-A
751.35 circled 1.gif 12" Minimum at gutter line top of concrete.
751.35 circled 2.gif All concrete in the end bent above top of beam and below top of slab shall be class B-2.
751.35 circled 3.gif Provide a minimum of 8" cl. from outside edge of pile to face of beam. For pile greater than 14” wide (dia.), shifting pile centerline towards fill face is preferred based on structural considerations (eccentric load to pile). Otherwise, increase abutment beam width (1” increments) towards front face in order to meet 8” min. cl.

Example:

Pile size = 16”

Option I (preferred): Shift pile centerline 1” towards fill face and consider eccentric load to the pile.

Min. abutment width = 20”+16”=3’-0”

Option II: Increase beam width 1” towards front face.

Min. abutment width = 21”+16”=3’-1”
751.35 circled 4.gif See Design Layout for maximum slope of spill fill.
(*) Keep 1 1/2" Min. clear cover for a #6 bar reinforcement between approach notch and girder. Increase abutment beam width (1" increments) to get the 1 1/2" clear cover if necessary.
(**) See Protective Barricades


751.35 prestressed girder end bent-detail of keyed const jt.gif
Detail of Keyed
Const. Jt.
 


751.35 prestressed girder end bent-elevation.gif
Elevation
 
751.35 prestressed girder end bent-plan (square).gif
Plan (Square)
 
751.35 prestressed girder end bent-plan (skewed).gif
Plan (Skewed)
Note: Neoprene bearing pads are to be used on integral bents (steel or prestressed structures) if pad size and beam clearance permit; otherwise, use girder chairs.
(*) 18" (Min.) 2'-0" (Max.); provide a minimum of 8" cl. from outside edge of pile to outside face of beam.

751.35.3.4 Steel Girder or Beam End Bent

751.35 steel girder or beam end bent-section near wing.gif 751.35 steel girder or beam end bent-section a-a.gif
Section Near Wing Section A-A
751.35 circled 1.gif 12" Minimum at gutter line top of concrete.
751.35 circled 2.gif All concrete in the end bent above top of beam and below top of slab shall be class B-2.
751.35 circled 3.gif Provide a minimum of 8" cl. from outside edge of pile to face of beam. For pile greater than 14” wide (dia.), shifting pile centerline towards fill face is preferred based on structural considerations (eccentric load to pile). Otherwise, increase abutment beam width (1” increments) towards front face in order to meet 8” min. cl.

Example:

Pile size = 16”

Option I (preferred): Shift pile centerline 1” towards fill face and consider eccentric load to the pile.

Min. abutment width = 20”+16”=3’-0”

Option II: Increase beam width 1” towards front face.

Min. abutment width = 21”+16”=3’-1”
751.35 circled 4.gif See Design Layout for maximum slope of spill fill.
(*) Use 3" Min. when girder chairs are used and use 1" past the end of the bearing pad when bearing pads are used.
(**) Keep 1 1/2" min. clear cover for a #6 bar reinf. between approach notch and girder. Increase abutment beam width (1" increments) to get the 1 1/2" clear cover if necessary.
(***) See Protective Barricades


751.35 steel girder or beam end bent-detail of keyed const jt.gif
Detail of Keyed
Const. Jt.
 


751.35 steel girder or beam end bent-elevation.gif
Elevation
 
751.35 steel girder or beam end bent-plan (square).gif
Plan (Square)
 
751.35 steel girder or beam end bent-plan (skewed).gif
Plan (Skewed)
Note: Neoprene bearing pads are to be used on integral bents (steel or prestressed structures) if pad size and beam clearance permit; otherwise, use girder chairs.
(*) 18" (Min.) 2'-0" (Max.); provide a minimum of 9" cl. from outside edge of pile to face of beam.
(*) 3" cl. between sole plate and keyed const. joint (Typ.)

751.35.3.5 Wing & Detached Wing Walls

751.35 wings and detached wing walls-wing.gif
 
751.35 wings and detached wing walls-detached wing.gif
 
751.35 wings and detached wing walls-section a-a.gif 751.35 wings and detached wing walls-detail c.gif
Section A-A Detail "C"
 
751.35 wings and detached wing walls-detail b.gif 751.35 wings and detached wing walls-section d-d.gif
Detail "B" Section D-D
(*) Detached wing wall shown is for illustration purpose only. Design detached wing wall as a LFD retaining wall (EPG 751.24).
(**) See EPG 751.24 LFD Retaining Walls.

751.35.4 Reinforcement

751.35.4.1 Wide Flange & Plate Girders

751.35 wide flange and plate girders-part section near end bent.gif
Part Section Near End Bent
751.35 wide flange and plate girders-section a-a.gif 751.35 wide flange and plate girders-section b-b.gif 751.35 wide flange and plate girders-section c-c.gif
Section A-A Section B-B Section C-C
751.35 wide flange and plate girders-section d-d.gif
  Place U1, U2, U3, U4, and V1 bars parallel to centerline Roadway.
751.35 circled 1.gif #6 U-bar 751.35 wide flange and plate girders--6-u-bar.gif (horiz. leg placed parallel to centerline Roadway) and #6 V-bar or U-bar @ 9" cts. min. (Between barrier curbs).
751.35 circled 2.gif #5-U4 at 12" cts. 751.35 wide flange and plate girders--5-u4-bar.gif - spaced with U1 and V1 bars.
751.35 circled 3.gif U1 at 12" cts. 751.35 wide flange and plate girders-u1-bar.gif - spaced between piles and girders. #5 bars, except special cases.
751.35 circled 4.gif See tables for 1 1/16" round hole spacing for #6 reinf. bars.
751.35 circled 5.gif Same number of bars as 1 1/16" round holes in stringer or girder.
751.35 circled 6.gif By design - development length (top bars) min.
751.35 circled 7.gif Stirrups shall clear step by 1 1/2" min., if not lengthen step or skew step.
751.35 circled 9.gif #5 bars, 2'-6" long, spaced at 12" cts. along centerline bent. Bars placed parallel to centerline Rdwy.
Section D-D
 
 
 

Place note on plans if Girder Chairs are used:

Shift the reinforcing steel to keep 1 1/2" clearance of the angles of the girder chairs.
Keep 1 1/2" clearance between shear reinforcement and piles.
(Replace U1 bars with U3 bars at piles under girders and with V1 bars at piles between girders.)

751.35.4.2 Prestressed Girders

751.35 prestressed girders-part section near end bent.gif
Part Section Near End Bent
751.35 prestressed girders-section a-a.gif 751.35 prestressed girders-section b-b.gif 751.35 prestressed girders-section c-c.gif
Section A-A Section B-B Section C-C
751.35 prestressed girders-section d-d.gif
  Place U1, U2, U3, U4, and V1 bars parallel to centerline Roadway.
751.35 circled 1.gif #6 U-bar 751.35 wide flange and plate girders--6-u-bar.gif (horiz. leg placed parallel to

centerline Roadway) and #6 V-bar or U-bar @ 9" cts. min. (Between barrier curbs).

751.35 circled 2.gif #5-U4 at 12" cts. 751.35 wide flange and plate girders--5-u4-bar.gif - spaced with U1 and V1 bars.
751.35 circled 3.gif U1 at 12" cts. 751.35 wide flange and plate girders-u1-bar.gif - spaced between piles and girders. (Replace U1 bars with U3 bars at piles under girders and with V1 bars at piles between girders). #5 bars, except special cases.
751.35 circled 4.gif By design - development length (top bars) min.
751.35 circled 6.gif #5 bars, 2'-6" long, spaced at 12" cts. along centerline bent. Bars placed parallel to centerline Rdwy.
Section D-D

Place note on plans if girder chairs are used:

Shift the reinforcing steel to keep 1 1/2" clearance of the angles of the girder chairs.
Keep 1 1/2" clearance between shear reinforcement and piles.

751.35.4.3 Wide Flange, Plate Girders & Prestressed Girders

751.35 wide flanges-plate girders and prestressed girders-elevation of wing.gif 751.35 wide flanges-plate girders and prestressed girders-part section thru wing.gif
Elevation of Wing Part Section
Thru Wing
(*) Keep a min. of 3" ctr. to ctr. spacing between #6 bars placed horizontally and #8 bars placed with grade.
751.35 circled 2.gif Use const. joint on steel structures only.
751.35 wide flanges-plate girders and prestressed girders-section a-a (square).gif 751.35 wide flanges-plate girders and prestressed girders-part section thru end of wing.gif
Section A-A (Square)
(K bars not shown for clarity)
Part Section Thru
End of Wing
751.35 circled 1.gif Use 90° standard hook in seismic areas.
751.35 wide flanges-plate girders and prestressed girders-part plan - skewed end bent.gif
Part Plan - Skewed End Bent
(**) Place note on plans
  Bend ____ F bars in field to clear girder.
Note: See barrier curb details and spacing of K bars.
  Prestressed I-Girders shown in details, Steel Girders similar.


751.35 wide flanges-plate girders and prestressed girders-section thru square end bent.gif 751.35 wide flanges-plate girders and prestressed girders-section thru skewed end bent.gif
Section Thru
Square End Bent
Section Thru
skewed End Bent
 
751.35 wide flanges-plate girders and prestressed girders-part plan of square end bent.gif 751.35 wide flanges-plate girders and prestressed girders-part plan of skewed end bent.gif
Plan
Square End Bent
Plan
Skewed End Bent
Note: Sections shown above are between girders and piles. Prestressed I girders are shown in the sections above; Steel girders are similar.
751.35 circled 1.gif Use same as bottom reinforcement.
751.35 circled 2.gif Use construction joint on steel structures only.

751.35.5 Details

751.35.5.1 Reinforcing Holes

Reinforcing Holes for Wide Flange Beams
751.35 details-section at end of stringer.gif 751.35 details-section a-a.gif
Section at End of Stringer Section A-A


WF Beam Depth Stud Spacing "A" Reinforcing Hole Spacing
21" 2 spa, @ 4/12" 4" 2 equal spaces
24" 2 spa. @ 6" 4" 2 equal spaces
27" 2 spa. @ 7 1/2" 4 1/2" 2 equal spaces
30" 3 spa. @ 6" 4 1/2" 3 equal spaces
33" 3 spa. @ 7" 4 1/2" 3 equal spaces
36" 4 spa. @ 6" 4 1/2" 3 equal spaces



Reinforcing Holes for Plate Girders
751.35 details-section at end of girder.gif
Section at End of Girder  
Note: Check the dead load (DL) on angles for girders 60" or larger.
  Bearing stiffeners are to be designed for DL1 (no SBC or FWS) and 50 psf construction load. (No web studs are required since bearing stiffener is provided).
(***) 1 1/16"ø holes for skews thru 20°. For skews > 20°, use slotted hole = 1 1/16" + 2(Web thickness)x(tan of the skew angle)


PL Girder Depth "A" Reinforcing Hole Spacing
39" 3 1/2" 4 equal spaces
42" 3 1/2" 5 equal spaces
48" 4" 5 equal spaces
54" 4 1/2" 6 equal spaces
60" 4" 8 equal spaces

751.35.5.2 Vertical Drains

751.35 vertical drains-elevation at end bent.gif
Elevation at End Bent
 
751.35 vertical drains-section a-a.gif 751.35 vertical drains-detail b.gif
Section A-A Detail "B"
 
751.35 vertical drains-detail c.gif 751.35 vertical drains-elevation of wing.gif
Detail "C" Elevation of Wing


751.35 vertical drains-elevation of wing1.gif 751.35 vertical drains-part plan.gif
Elevation of Wing Part Plan
Optional Bent Drain (*)
(*) Only if rock is encountered at outside of wings.