FDOT Standard Plans Index 400-510: Composite Elastomeric Bearing Pads - Prestressed Florida - I and AASHTO Type II Beams

Design Criteria

Design Criteria AASHTO LRFD Bridge Design Specifications ; Structures Design Guidelines ( SDG )

Design Assumptions and Limitations

Design Assumptions and Limitations This standard depicts details and notes for elastomeric bearing pads for prestressed concrete Florida - I and AASHTO Type II Beams with or without skewed end conditions. This standard is intended for use with prestressed concrete Florida - I and AASHTO Type II Beams, but may be used for steel girder or other bridge types with the appropriate notes and cross references. This standard may be used with Indexes 45 0 - 010, 45 0 - 036, 45 0 - 045, 45 0 - 054, 45 0 - 063, 45 0 - 072, 45 0 - 078, 45 0 - 084, 45 0 - 096, 45 0 - 120, 45 0 - 511 and 45 0 - 512.

Beveled Bearing Plates B are required for beams on grades greater than 2%, see instructions for Index 45 0 - 511 and/or 45 0 - 512. LIMITING PARAMETERS FOR COMPOSITE ELASTOMERIC BEARING PADS USED WITH FDOT STANDARD FLORIDA - I AND AASHTO TYPE II BEAMS Pad Type Maximum Service Live Load (kips) Maximum Service Dead Load (LL = Actual Service Live Load) Bearing Skew Angle (degrees) Maximum Shear Deflection (in) Shear Modulus, G (Psi) AA 65 DL=85+1.75(65 - LL) 0 - 15 0.75 110 AB 85 DL=95+1.75(85 - LL) 0 - 30 1.0 150 D 135 DL=147+1.75(135 - LL) 0 - 5 0.75 110 110 DL=120+1.75(110 - LL) 0 - 15 E 150 DL=233+1.75(150 - LL) 0 - 5 0.75 110 110 DL=113+1.75(110 - LL) 0 - 20 F 150 DL=290+1.75(150 - LL) 0 - 5 1.0 110 120 DL=139+1.75(120 - LL) 0 - 30 G 145 DL=230+1.75(145 - LL) 0 - 30 1.0 150 95 DL=98+1.75(95 - LL) 0 - 45 H 180 DL=268+1.75(180 - LL) 0 - 35 1.25 150 135 DL=230+1.75(135 - LL) 0 - 45 J 145 DL=227+1.75(145 - LL) 0 - 45 1.5 150 K 200 DL=383+1.75(200 - LL) 0 - 45 1.5 150 Standard Plan s Instructions Topic No. 625 - 010 - 003 Index 400 - 510 Composite Elastomeric Bearing Pads - Prestressed Florida - I and AASHTO Type II Beams Skew angle for Bearing Pad design is based on the direction of rotation with respect to the centerline of the Bearing Pad; and is usually taken as the angle between the centerline of the beam and the longitudinal centerline of the Bearing Pad, except on cu rved bridges.

The Service Live Load (including impact) and Service Dead Load Reactions can be determined from the beam design. The Shear Deflection is the product of the coefficient of thermal expansion, 65% of the thermal gradient and the length of bridge contributing to movement, plus the contributing beam creep and shrinkage at the bottom of beam. Assume beam creep and shrinkage from day 120 to day 240 (this value can be determined from data in the beam design output).

Standard Elastomeric bearing pads have been designed in accordance with the AASHTO LRFD Bridge Design Specifications , Method "B" , for a maximum static rotation (beam grade, camber and dead load rotation) of 0.0125 radians and a cyclic rotation (live load) of 0.004 radians. Live load rotations are assumed to be in the opposite direction to static rotations. Rotation does not need to b e checked for standard prestressed beams provided that the top of the beveled bearing plates (when required) or the bearing se ats (pedestals) are finished approximately parallel to the slope of the beam.

The effects of camber (at day 120) from prestressing and dead load deflection may be neglected when determining the slope at the ends of the beam, unless the sum of these effects exceeds 0.0125 radians (1.25%). Bearing seats may be finished level for beam grades less than 0.5%, or when the combined effects of beam grade, camber and dead load rotation do not exceed 1.25%. Whenever possible, the bearing seats at each end of the beam should be detailed with the same slope.

See also instructions for Index 45 0 - 511. For design values exceeding the limiting parameters shown on this sheet, the designer must develop custom designs and details. For skew angles greater than 45°, consider round pads with elastomer and plate thicknesses similar to those shown in Index 40 0 - 510.

Payment

Payment Item number Item Description Unit Measure 400 - 147 Composite Neoprene Pads CF Standard Plan s Instructions Topic No. 625 - 010 - 003 Index 400 - 510 Composite Elastomeric Bearing Pads - Prestressed Florida - I and AASHTO Type II Beams Examples The following examples show the information required to determine the correct standard elastomeric bearing pad type to use. These examples do not assume any wind or braking loads are applied to the elastomeric bearing pads.

EXAMPLE 1 Given Information: Superstructure Type - One Simple Span 45" Florida I Beams 101' - 0" long, spaced at 9' - 0" centers (99' - 8" center to center bearing) No longitudinal restraints except friction between the pad and the concrete substructure Service Live Load Reaction = 106 kips Service Dead Load Reaction = 109 kips Coefficient of Thermal Expansion = 0.000006/°F Thermal Gradient = 70°F Creep and Shrinkage at the Bottom of Beam (from day 120 to day 240) = 0.28" Shear Deflection = (0.000006/°F x 0.65 x 70°F x 99.67'/2 x 12"/') + 0.280"/2 = 0.30" Beam Grade = 2.0% Bearing Pad Skew Angle = 15° Service Dead Load Rotation = 0.007 radians (0.7%) Beam Camber Rotation @ 120 days = 0.012 radians (1.2%) Net Beam Camber Rotation after Dead Load Deflection = 0.012 - 0.007 = 0.005 radians (0.5%) Elastomeric Bearing Pad Type Determination: Compare the design values to the Limiting Parameters Table, Pad Type D for Florida - I Beams. Check Net Static Rotation (assuming sloped bearing seat) = 0.000+0.005 < 0.0125 radians; therefore, OK Limiting Parameters versus Design Values: Maximum Service Live Load Reaction of 110 kips versus Design Value of 106 kips; therefore, OK Maximum Service Dead Load Reaction of 120+1.75(110 - 106) = 127 kips versus Design Value of 109 kips; therefore, OK Maximum Shear Deflection of 0.75" versus Design Value of 0.30"; therefore, OK Skew Angle is between 0° and 15°; therefore, OK Conclusion: Use Elastomeric Bearing Pad Type D. Standard Plan s Instructions Topic No.

625 - 010 - 003 Index 400 - 510 Composite Elastomeric Bearing Pads - Prestressed Florida - I and AASHTO Type II Beams No beveled plate is required. Detail beam seat with a 2% slope along the centerline of beam. Complete "BEARING PLATE DATA TABLE" for embedded bearing plate only, see instructions for Index 450 - 511 and/or 450 - 512 .

EXAMPLE 2 Given Information: Superstructure Type - Four Simple Spans with Continuous Deck 45" Florida I Beams 101' - 0" long, spaced at 9' - 0" centers (99' - 8" center to center bearing) No longitudinal restraints except friction between the pad and the concrete substructure Service Live Load Reaction = 106 kips Service Dead Load Reaction = 109 kips Coefficient of Thermal Expansion = 0.000006/°F Thermal Gradient = 70°F Creep and Shrinkage at the Bottom of each Beam (from day 120 to day 240) = 0.28" Shear Deflection = (0.000006/°F x 65% x 70°F x 202' x 12"/') + 0.280"/2 = 0.80" Beam Grade = 5% Bearing Pad Skew Angle = 15° Service Dead Load Rotation = 0.007 radians (0.7%) Beam Camber Rotation @ 120 days = 0.012 radians (1.2%) Net Beam Camber Rotation after Dead Load Deflection = 0.012 - 0.007 = 0.005 radians (0.5%) Elastomeric Bearing Pad Type Determination: Compare the design values to the Limiting P arameters Table, Pad Type F for Florida - I Beams. Limiting Parameters versus Design Values: Maximum Service Live Load Reaction of 120 kips versus Design Value of 106 kips; therefore, OK Maximum Service Dead Load Reaction of 139+1.75(120 - 106) = 163.5 kips versus Design Value of 109 kips; therefore, OK Maximum Shear Deflection of 1.0" versus Design Value of 0.80"; therefore, OK Skew angle is between 0° and 30°; therefore, OK Conclusion: Use Elastomeric Bearing Pad Type F. Additionally, because beam end slope exceeds 2%, include a beveled bearing plate in the "BEARING PLATE DATA TABLE" and detail bearing seats level, see instructions for Index 450 - 511 and/or 450 - 512 .

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What your plans must show

Plan Content Requirements for this index — the SPI's checklist for designers.

• In the Structures Plans: Complete the "BEARING PAD DATA TABLE" and include the table on the supplemental sheets. See FDM 115 for more information regarding use of Data Tables. The "BEARING PAD DATA TABLE" is intended for use with prestressed beam bridges, but may be modified for steel girder or other bridge types. Supplement this table with additional columns or notes as required to clearly identify the location and type of bear ing pads. For beam grades greater than 2%, provide beveled bearing plates in accordance with Index 45 0
• - 511 and include a "BEARING PLATE DATA TABLE" in the plans.
• Standard Plan s Instructions Topic No. 625
• - 510 Composite Elastomeric Bearing Pads
• - I and AASHTO Type II Beams