751.32.1 General
751.32.1.1 Material Properties
Concrete
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Typically, shall consist of:
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Class B Concrete (Substructure) |
![{\displaystyle \,f'_{c}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/f2c29803c2cd1260bd139317dd2903cf7a6be2f6) |
= 3.0 ksi
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![{\displaystyle \,n}](https://wikimedia.org/api/rest_v1/media/math/render/svg/a798350c07bbc4b91b4190498a18535149176d01) |
= 10
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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:
Where:
![{\displaystyle \,w_{c}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/ba6862af1365b165a49cc3b56dd34db807faaa35) |
= unit weight of non-reinforced concrete = 0.145 kcf
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![{\displaystyle \,K_{l}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/2f8d07aab1449795b52abf02585580f970aa55b8) |
= correction factor for source of aggregate = 1.0
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Modulus of Rupture: |
For minimum reinforcement, |
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For all other calculations, |
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is in units of ksi |
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Reinforcing Steel
Minimum yield strength, |
![{\displaystyle \,f_{y}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/4eea7b7c0367399c141998a45ffc8b00faeba281) |
= 60.0 ksi
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Steel modulus of elasticity, |
![{\displaystyle \,E_{s}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/8700afe0d95b2b0e1c20590ac4ae0c9e8f137cca) |
= 29000 ksi
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751.32.2 Design
751.32.2.1 Limit States and Factors
In general, each component shall satisfy the following equation:
Where:
![{\displaystyle \,Q}](https://wikimedia.org/api/rest_v1/media/math/render/svg/3eca89004fd0e5c9900221419c82c6243e46a49a) |
= Total factored force effect
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![{\displaystyle \,Q_{i}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/deedaacf11f1a003a771aa8fab3a5b7f91c735fd) |
= Force effect
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![{\displaystyle \,\eta }](https://wikimedia.org/api/rest_v1/media/math/render/svg/ed57dc0df65ee5f955ac47d2f1e9374af5417253) |
= Load modifier
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![{\displaystyle \,\gamma _{i}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/5b3970858c06a68f6bcc96afdb4c1bfdbdb071e9) |
= Load factor
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![{\displaystyle \,\phi }](https://wikimedia.org/api/rest_v1/media/math/render/svg/2691650573917bbe9b3d1c28ecfb49275110d16c) |
= Resistance factor
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![{\displaystyle \,R_{n}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/f0330c216fe72940fe0b79ae6589365bcbc862e0) |
= Nominal resistance
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![{\displaystyle \,R_{r}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/661067f7f95b46a634668123b3c48b771c0677e3) |
= Factored resistance
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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,
= 1.00
Load Modifiers
751.32.3 Details
751.32.3.1 Front Sheet
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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.
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Details for unsymmetrical roadways shall require dimensions tying Centerline Lane to Centerline Structure.
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751.32.3.2 Typical Pile Cap Bent
![751.32 details-part elevation.gif](/files/8/8e/751.32_details-part_elevation.gif) |
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(*) 3" (Typ.)
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Part Elevation |
Part Section
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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).
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= 2'-9" (Min.) for Wide Flange and Double-Tee Girders or, 3'-0" (Min.) for Prestressed Girders and Plate Girders.
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Check the clearance of the anchor bolt well to the top of pile. Increase the beam depth if needed.
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If the depth at the end of the beam, due to the steps, exceeds 4'-6", the beam bottom should be stepped or sloped.
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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.
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Minimum of 3 piles at 10'-0" cts., maximum spacing (1" increments).
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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.
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Part Elevation
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Part Section
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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).
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= 2'-9" (Min.) for Wide Flange and Double-Tee Girders or, 3'-0" (Min.) for Prestressed Girders and Plate Girders.
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Check the clearance of the anchor bolt well to the top of pile. Increase the beam depth if needed.
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If the depth at the end of the beam, due to the steps, exceeds 4'-6", the beam bottom should be stepped or sloped.
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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.
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Minimum of 3 piles at 10'-0" cts., maximum spacing (1" increments).
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751.32.4 Reinforcement
751.32.4.1 Typical Pile Cap Bent
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Part Elevation |
Section Thru Beam
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Part Plan |
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Note: |
Locate #4 bars " " under bearings where required to maintain a 6" maximum spacing of combined stirrups. (#4 bars " " are not required for Double-Tee Structures.)
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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.
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* #4 Bars ( ) not required for Double-Tee structures
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Reinforcement Under Bearings
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Transverse Beam Steps - Over 3" or Steps Accumulating Over 3"
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Part Plan
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Over 3" thru 12" |
Over 12"
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Longitudinal Beam Steps
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751.32.4.2 Encased Pile Cap Bent
Supplemental details for encased pile cap bents are provided.
Note: |
Locate #4 bars " " under bearings where required to maintain a 6" maximum spacing of combined stirrups. (#4 bars " " are not required for Double-Tee Structures.)
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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.
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