751.35 Concrete Pile Cap Integral End Bents

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:

Modulus of elasticity,

$E_{c}=33,000\ K_{1}\ (w_{c}^{1.5}){\sqrt {f_{c}^{'}}}$

Where:

f'_c in ksi

w_c = unit weight of nonreinforced concrete = 0.145 kcf

K₁ = correction factor for source of aggregate

= 1.0 unless determined by physical testing

Modulus of rupture,

$f_{r}\ =\ 0.24{\sqrt {f'_{c}}}$       LRFD 5.4.2.6

Where:

f'_c is in 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:

$\,Q=\sum \eta _{i}\gamma _{i}Q_{i}\leq \phi R_{n}=R_{r}$

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 beams, 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 beams, 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 751.2.2.6.

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.

File: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.

File: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.

$\,M_{u}=0.2R_{u}L+0.13WL^{2}$

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.

File: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.

File: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.

File: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.

File: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.

File:751.35 wing brace details-skews 0 thru 45.gif
Skews 0° thru 45°
File:751.35 wing brace details-skews 45 thru 55.gif
Skews 45°00'01" thru 55°
File: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

(1) See EPG 751.12 Protective Barriers for barrier curb details.

(2) Keep 1 1/2" minimum clear cover for reinforcement between approach notch and girder. Increase beam width (1" increments) to get the 1 1/2" clear cover if necessary.

(3) Use 1” plus half of bearing pad length when bearing pads are used. Use 3 ½” minimum for NU Standard Girders and 5” minimum for MoDOT Standard Girders when girder chairs are used.

(4) 12" minimum at gutter line at end of slab.

(5) All concrete in the end bent above top of beam and below top of slab shall be Class B-2.

(6) Provide a minimum of 8" clearance from outside edge of pile to face of beam. For pile greater than 14” wide (diameter), shifting pile centerline towards fill face is preferred based on structural considerations (eccentric load to pile). Otherwise, increase beam width (1” increments) toward front face in order to meet 8” minimum clearance.

Example:

Pile size = 16”

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

Minimum beam width = 20”+16”=3’-0”

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

Minimum beam width = 21”+16”=3’-1”

(7) See Design Layout for maximum spill slope.

Note:	Neoprene bearing pads are to be used on integral bents (prestressed structures) if pad size and beam clearance permit; otherwise, use girder chairs. See EPG 751.11.3.6 Girder/Beam Chairs for additional girder chair details.
	Squared beam steps are shown. Steps may be skewed to facilitate placement of U1 and V1 stirrup bars. See EPG 751.35.4 Reinforcement for details.
*	18" minimum, 2'-0" maximum; provide a minimum of 8" clearance from outside edge of pile to outside face of beam.

751.35.3.4 Steel Girder or Beam End Bent

(1) See EPG 751.12 Protective Barriers for barrier curb details.

(2) Keep 1 1/2" minimum clear cover for reinforcement between approach notch and girder. Increase abutment beam width (1" increments) to get the 1 1/2" clear cover if necessary.

(3) Use 1" plus half of bearing pad length when bearing pads are used. Use 3" minimum when girder chairs are used.

(4) 12" minimum at gutter line at end of slab.

(5) All concrete in the end bent above top of beam and below top of slab shall be Class B-2.

(6) Provide a minimum of 8" clearance from outside edge of pile to face of beam. For pile greater than 14” wide (diameter), shifting pile centerline toward fill face is preferred based on structural considerations (eccentric load to pile). Otherwise, increase beam width (1” increments) toward front face in order to meet 8” minimum clearance.

Example:

Pile size = 16”

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

Minimum beam width = 20”+16”=3’-0”

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

Minimum beam width = 21”+16”=3’-1”

(7) See Design Layout for maximum spill slope.

Note:	Neoprene bearing pads are to be used on integral bents (steel structures) if pad size and beam clearance permit; otherwise, use girder chairs. See EPG 751.11.3.6 Girder/Beam Chairs for additional girder chair details.
	Squared beam steps are shown. Steps may be skewed to facilitate placement of U1 and V1 stirrup bars See EPG 751.35.4 Reinforcement for details.
*	18" minimum, 2'-0" maximum; provide a minimum of 8" clearance from outside edge of pile to outside face of beam.
**	3" minimum clearance between sole plate and keyed construction joint (typical)

751.35.3.5 Wing & Detached Wing Walls

Section A-A	Detail "C"
Detail B	Section D-D

Note:

*	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.
Report Pile Cut-off Elevation and Minimum Galvanized Penetration (Elev.) (See Foundation Data).

751.35.4 Reinforcement

For epoxy coated reinforcement requirements, see EPG 751.5.9.2.2 Epoxy Coated Reinforcement Requirements.

751.35.4.1 Wide Flange Beams & Plate Girders

	Detailing Guidance:
	ko	Green items are guidance only and shall not be shown plans.
		Place all U bars and V pairs parallel to centerline roadway.
		Keep 1 1/2" clearance between the piles and the U1 or U2 bars.
		Keep 1 1/2" clearance between the beams or girders and the U1 or V1 bars.
		Keep 1 1/2" clearance between the angles of girder chairs and the U2 or U3 bars.
		Replace U1 bars with U3 bars at piles under beams or girders.
		Replace U1 bars with V1 bars at piles between beams or girders.
		See EPG 751.50 G1 Concrete Bents for appropriate notes to be placed with details.
		(1)	#6-U bar (File:751.35 wide flange and plate girders--6-u-bar.gif) at 9" centers between barrier curbs. For shallow beams where 26” is not available extend to top of beam minus 1” clear.
		(2)	U4 bars (13px) and #6-U5 bars (File:751.35 wide flange and plate girders--6-u-bar.gif) spliced with U1 (File:751.35 wide flange and plate girders-u1-bar.gif) and V1 bars (│). U4 bars shall be same size as U1 bars. Show lap splice on plans as shown. For shallow beams stirrup hooks may be required for U4 bars () (see Alternate Sections). For shallow beams where 16” is not available extend stirrup hooks to top of beam minus 1” clear.
		(3)	U1 bars (File:751.35 wide flange and plate girders-u1-bar.gif) at 12" centers. Typically #5 bars, except special cases. Replace with pairs of #5-V1 bars (│) at piles. Make sure U1 and V1 bars extend enough to meet lap length requirement across length of diaphragm. For shallow beams stirrup hooks may be required for U1 bars () and end hooks may be required for V1 bars () (see alternate sections). For shallow beams where 16” is not available extend hooks to approach notch minus 1 1/2" clear.
		(4)	Stirrups shall clear step by 1 1/2" minimum, if not lengthen step or skew step.
		(5)	#6-V bars at no more than 9” centers at the end of girders or beams.
		(6)	#5-U bars (15”H x 24”V) @ about 12" centers placed parallel to centerline roadway. When approach slab haunch is expected to be greater than 18” at the roadway crown at the end of slab, slope the approach slab notch providing 12” of constant approach slab haunch or with SPM or SLE approval greater than 18” approach slab haunch may be used but increase vertical leg length of #5-U bars to ensure 12” minimum embedment. For shallow beams where 12” embedment is not available adjust length of vertical leg and extend to top of beam minus 1” clear.
		(7)	With SPM or SLE approval a 29” splice may be used in combination with specifying 2” cover to U bars and V bars if doing so avoids the need for using hooked bars.
		(8)	See tables for 1 1/16" round hole spacing for #6-H bars.
		(9)	Same number of bars as 1 1/16" round holes in beam or girder.

751.35.4.2 Prestressed I-Girders, Bulb-Tee Girders and NU-Girders

	Detailing Guidance:
	ko	Green items are guidance only and shall not be shown plans.
		Place all U bars and V pairs parallel to centerline roadway.
		Keep 1 1/2" clearance between the piles and the U1 or U2 bars.
		Keep 1 1/2" clearance between the beams or girders and the U1 or V1 bars.
		Keep 1 1/2" clearance between the angles of girder chairs and the U2 or U3 bars.
		Replace U1 bars with U3 bars at piles under beams or girders.
		Replace U1 bars with V1 bars at piles between beams or girders.
		See EPG 751.50 G1 Concrete Bents for appropriate notes to be placed with details.
		(1)	#6-U bar (File:751.35 wide flange and plate girders--6-u-bar.gif) at 9" centers between barrier curbs. For shallow beams where 26” is not available extend to top of beam minus 1” clear.
		(2)	U4 bars (13px) and #6-U5 bars (File:751.35 wide flange and plate girders--6-u-bar.gif) spliced with U1 (File:751.35 wide flange and plate girders-u1-bar.gif) and V1 bars (│). U4 bars shall be same size as U1 bars. Show lap splice on plans as shown. For shallow beams stirrup hooks may be required for U4 bars () (see Alternate Sections). For shallow beams where 16” is not available extend stirrup hooks to top of beam minus 1” clear.
		(3)	U1 bars (File:751.35 wide flange and plate girders-u1-bar.gif) at 12" centers. Typically #5 bars, except special cases. Replace with pairs of #5-V1 bars (│) at piles. Make sure U1 and V1 bars extend enough to meet lap length requirement across length of diaphragm. For shallow beams stirrup hooks may be required for U1 bars () and end hooks may be required for V1 bars () (see alternate sections). For shallow beams where 16” is not available extend hooks to approach notch minus 1 1/2" clear.
		(4)	Stirrups shall clear step by 1 1/2" minimum, if not lengthen step or skew step.
		(5)	#6-V bars at no more than 9” centers at the end of girders or beams.
		(6)	#5-U bars (15”H x 24”V) @ about 12" centers placed parallel to centerline roadway. When approach slab haunch is expected to be greater than 18” at the roadway crown at the end of slab, slope the approach slab notch providing 12” of constant approach slab haunch or with SPM or SLE approval greater than 18” approach slab haunch may be used but increase vertical leg length of #5-U bars to ensure 12” minimum embedment. For shallow beams where 12” embedment is not available adjust length of vertical leg and extend to top of beam minus 1” clear.
		(7)	With SPM or SLE approval a 29” splice may be used in combination with specifying 2” cover to U bars and V bars if doing so avoids the need for using hooked bars.

751.35.4.3 Wing Reinforcement

Detailing Guidance:

Green items are guidance only and shall not be shown on plans.

Bar marks shown are for these details only. Vary as needed.

K bars not shown in the Elevation of Wing for clarity. See EPG 751.12.2.3 for details of K bars at integral end bents.

See EPG 751.3.3 for chamfer detail.

(a) Use dimension that provides a minimum of 3" center to center spacing between #6 bars placed horizontally and #8 bars placed with grade. See SPM or SLE if spacing at one end exceeds 8 inches due to grade.

(b) Use construction joint on steel structures only.

(c) 6 3/8” min and 11 3/8” max. If unable to get dimension to fall within this range using 8-inch centers, then use 6 3/8” and use “@ abt. 8” cts.”

(d) Use 66.5” for obtuse corner of bents skewed 55 degrees or greater.

(e) Use 54.5” for obtuse corner of bents skewed 55 degrees or greater.

(f) See EPG 751.50 G1 Concrete Bents for note required for the #6-F bars.

(g) Use 90 degree standard hook in seismic areas.

751.35.4.4 Skewed Bents

Prestressed I-girders shown in the following details, steel structures are similar.

The sections thru integral end bents previously shown shall be adjusted for skew as shown.

751.35.5 Details

751.35.5.1 Reinforcing Holes

Reinforcing Holes for Wide Flange Beams

	File:751.35 details-section a-a.gif
Section at End of Beam	Section A-A

WF Beam Depth	Stud Spacing	A	Reinforcing Hole Spacing
21"	2 spa, @ 4 1/2"	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

Section at End of Girder

Note:	Bearing stiffeners are to be designed for DC (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

Bridge Standard Drawings

Vertical Drain at End Bents