Concrete Roadside Barrier Anchorage Details for 5-in., Cast-in-Place Decks on Prestressed Beams
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The Texas Department of Transportation commonly builds bridge spans with adjacently framed, prestressed box beams and slab beams and makes them composite with a 5-in.-thick, concrete, cast-in-place deck (CIPD). The presence of a cast-in-place, concrete overlay allows use of more favorable empirical, live-load distribution equations, which results in more efficient bridge spans. This 5-in.-thick CIPD offers limited depth for anchorage of rail reinforcement. AASHTO Load and Resistance Factor Design Bridge Design Specifications has a limiting hook development length of 6 in. for a No. 4 rail anchorage. With a 5-in. deck thickness and a 6-in. minimum required development length, the rail anchorage reinforcement must be cast in the pretensioned beams to meet specification requirements for rail anchorage strength. This need has made it difficult to ensure adequate development of the rail anchorage reinforcement. The objective of the study reported here, therefore, was to develop barrier anchorage details that would meet the AASHTO Manual for Assessing Safety Hardware (MASH) evaluation criteria, minimize damage to the concrete barrier profile and CIPD, and prevent delamination of the CIPD from the precast beams, which was witnessed in a research project performed at Texas Transportation Institute. The anchorage modifications were evaluated successfully under the Manual for Assessing Safety Hardware Test 311 and were considered suitable for roadways with traffic conditions appropriate for Testing Level 3 safety hardware.
