751.32 Concrete Pile Cap Intermediate Bents

751.32.1 General

751.32.1.1 Material Properties

Concrete
Typically, shall consist of:
	Class B Concrete (Substructure)	$\,f'_{c}$	= 3.0 ksi
		$\,n$	= 10

In addition, 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:

$\,E_{c}=33000K_{l}w_{c}{\sqrt[{1.5}]{f'_{c}}}$

Where:

$\,w_{c}$	= unit weight of non-reinforced concrete = 0.145 kcf
$\,K_{l}$	= 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

751.32.2 Design

751.32.2.1 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
$\,\eta$	= 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 bent design:

STRENGTH – I

STRENGTH – III

STRENGTH – IV

STRENGTH – V

SERVICE – I

FATIGUE

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

For all other limit states, $\,\phi$ = 1.00

Load Modifiers

751.32.3 Details

751.32.3.1 Front Sheet

Note:	The following are details and dimensions for the plan view of a typical pile cap bent on the front sheet of the bridge plans. Details and dimensions for an encased concrete pile cap bent are similar.
	Details for unsymmetrical roadways shall require dimensions tying Centerline Lane to Centerline Structure.

File:751.32 details-front sheet plan of int bent.gif

751.32.3.2 Typical Pile Cap Bent

(*) 3" (Typ.)
Part Elevation	Part Section

File:751.32 circled 1.gif	Use 2'-6" minimum or as determined by the superstructure requirements or the minimum support length required for earthquake criteria (expansion joint bents only) (3" increments).
File:751.32 circled 2.gif	= 2'-9" (Min.) for Wide Flange and Double-Tee Girders or,    3'-0" (Min.) for Prestressed Girders and Plate Girders.
File:751.32 circled 3.gif	Check the clearance of the anchor bolt well to the top of pile. Increase the beam depth if needed.
File:751.32 circled 4.gif	If the depth at the end of the beam, due to the steps, exceeds 4'-6", the beam bottom should be stepped or sloped.
File:751.32 circled 5.gif	Use 3/4" drip groove where expansion device is located at bent. Continue to use 1-1/2" clear to reinforcing steel in bottom of beam. 3/4" drip groove shall be formed continuously around all piling at 3" from edge of beam.
File:751.32 circled 6.gif	Minimum of 3 piles at 10'-0" cts., maximum spacing (1" increments).

751.32.3.3 Encased Pile Cap Bent

Consideration shall be given to EPG 751.1.2.19 Substructure Type before using this type of structure.

Part Elevation
Part Section

File:751.32 circled 1.gif	Use 2'-6" minimum or as determined by the superstructure requirements or the minimum support length required for earthquake criteria (expansion joint bents only) (3" increments).
File:751.32 circled 2.gif	= 2'-9" (Min.) for Wide Flange and Double-Tee Girders or,    3'-0" (Min.) for Prestressed Girders and Plate Girders.
File:751.32 circled 3.gif	Check the clearance of the anchor bolt well to the top of pile. Increase the beam depth if needed.
File:751.32 circled 4.gif	If the depth at the end of the beam, due to the steps, exceeds 4'-6", the beam bottom should be stepped or sloped.
File:751.32 circled 5.gif	Height by design. Embed encasement 2 ft. (min.) below the top of the lowest finished groundline elevation, unless a greater embedment is required for bridge design.
File:751.32 circled 6.gif	Minimum of 3 piles at 10'-0" cts., maximum spacing (1" increments).

751.32.4 Reinforcement

751.32.4.1 Typical Pile Cap Bent

File:751.32 reinforcement-part elevation.gif	File:751.32 reinforcement-section thru beam.gif
Part Elevation	Section Thru Beam
File:751.32 reinforcement-part plan.gif
Part Plan

Note:	Locate #4 bars "File:751.32 reinforcement--4 bar under bearing.gif" under bearings where required to maintain a 6" maximum spacing of combined stirrups. (#4 bars "File:751.32 reinforcement--4 bar under bearing.gif" are not required for Double-Tee Structures.)
	When an expansion device is used at an intermediate bent, all reinforcement located entirely within the beam or extending into the beam shall be epoxy coated.

File:751.32 reinforcement under bearings-part elevation.gif	File:751.32 reinforcement under bearings-part plan.gif
	* #4 Bars (File:751.32 reinforcement--4 bar under bearing.gif) not required for Double-Tee structures
Reinforcement Under Bearings
File:751.32 transverse beam steps.gif
Transverse Beam Steps - Over 3" or Steps Accumulating Over 3"

File:751.32 reinforcement at end of beam-part plan.gif
Part Plan
Over 3" thru 12"	Over 12"
Longitudinal Beam Steps

751.32.4.2 Encased Pile Cap Bent

Supplemental details for encased pile cap bents are provided.

Part Elevation

Part Section

Part Plan

Note:	Locate #4 bars "File:751.32 reinforcement--4 bar under bearing.gif" under bearings where required to maintain a 6" maximum spacing of combined stirrups. (#4 bars "File:751.32 reinforcement--4 bar under bearing.gif" are not required for Double-Tee Structures.)
	When an expansion device is used at an intermediate bent, all reinforcement located entirely within the beam or extending into the beam shall be epoxy coated.