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Section 2: Concrete Deck Slabs on I-Girders, U-Beams, Spread Box Beams, Spread Slab Beams, Steel Plate Girders, and Steel Tub Girders

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Materials

Use Class S concrete (fc ́ = 4.0 ksi). Refer to district-specific corrosion protection requirements for regions where bridge decks are exposed to de-icing agents and/or saltwater spray with regularity. If thus required, use Class S (HPC) concrete.

Use Grade 60 reinforcing steel or deformed welded wire reinforcement (WWR) meeting the requirements of ASTM A1064. Refer to district-specific corrosion protection requirements for regions where bridge decks are exposed to de-icing agents and/or saltwater spray with regularity. If thus required, use one of the following types of corrosion resistant reinforcement (refer also to Item 440):

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  • Epoxy-Coated Reinforcing Steel meeting the requirements of ASTM A775 or A934
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  • Epoxy-Coated WWR meeting the requirements of ASTM A884 Class A or B
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  • Hot-Dip Galvanized Reinforcing Steel
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  • Glass Fiber Reinforced Polymer (GFRP) Bars; The design for GFRP reinforcement in bridge decks must adhere to the AASHTO LRFD Guide Specifications for GFRP-Reinforced Concrete Bridge Decks and Traffic Railings.
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  • Dual Coated Reinforcing Steel meeting the requirements of ASTM A1055
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  • Low Carbon/Chromium Reinforcing Steel meeting the requirements of ASTM A1035 Gr 100 Ty CS
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  • Stainless Reinforcing Steel meeting the requirements of ASTM A955 Ty 316LN, XM-28, 2205, or 2304; Use only for extreme chloride exposure in coastal areas.
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Geometric Constraints

TxDOT standard deck slab is 8.5 in. deep. Use of thinner concrete decks is not permitted.

Cover to reinforcing bars is 2.5 in. clear to the top mat and 1.25 in. clear to the bottom mat. Cover to bar ends is 2 in.

Maximum overhang is 3.33 ft. beyond the design section for negative moment specified in Article 4.6.2.1.6, but not more than 1.3 times the girder depth.

Minimum overhang is 0.5 ft. from top beam or flange edge except for spread slab and spread box beams, which have a 0 ft. minimum overhang.

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Design Criteria

Where applicable, use the Empirical Design of Article 9.7.2 with the following exceptions:

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  • Top mat reinforcement is No. 4 bars at 9 in. maximum spacing (0.27 sq. in./ft.) in both transverse and longitudinal direction. Place longitudinal bars closest to the top slab surface. In the overhangs, place No. 5 bars extending 2 ft. minimum past fascia girder web centerline between each transverse No. 4 bar.
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  • Bottom mat reinforcement is No. 4 bars at 9 in. maximum spacing (0.27 sq. in./ft.) in both transverse and longitudinal directions. Place transverse bars closest to the bottom slab surface.
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  • Slab regions adjacent to expansion joints are reinforced as shown on the standard drawings depicting thickened slab end details. No additional reinforcement in end regions, including those skewed over 25°, is needed in these cases. These standard drawings are:
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  • Cross-frames or diaphragms are not needed at supports for any prestressed concrete beam or girder.
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  • Do not provide supplemental reinforcement over the webs of U-beams or steel tub girders.
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  • The deck does not need to be fully cast-in-place and can utilize stay-in-place concrete formwork such as prestressed deck panels shown on standard drawing PCP.
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  • The overhang need not extend past the exterior girder more than 6 in. beyond the flange edge (0 in. for spread slab or spread box beams). An overhang is not required for girders and beams for the temporary condition of having a stage or phase construction joint located on top of their flange.

Use the Traditional Design of Article 9.7.3 where the provisions listed above for empirical deck use are not met. The minimum amount of longitudinal reinforcement in the top mat is No. 4 bars at 9 in. maximum spacing for these deck designs.

Overhang strength for extreme events, per Article 9.5.5, is satisfied through TxDOT’s rail crash testing.

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Detailing

Place main reinforcing steel parallel to the skew up to 15 degree skews. Place reinforcing steel perpendicular to beams for skews more than 15°, and use corner breaks.

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