United States Department of Transportation
i
Evaluation of Design Loads for Concrete Bridge Rails
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2016-03-01
[PDF-1.25 MB]
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TRIS Online Accession Number:1644634
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Abstract:Crash test standards for bridge rails now adhere to the Manual for Assessing Safety Hardware (MASH), which describes the required vehicles for Test Level 4 (TL-4) and Test Level 5 (TL-5). TL-5 conditions have not been changed relative to the predecessor standard, but the TL-4 vehicle has increased in mass, prompting some to consider whether or not the AASHTO transverse design loads on bridge rails should also increase. Increased transverse loads would lead to heavier bridge rails and stronger deck overhangs, which will increase the costs for bridge construction. This report presents a modified approach to the yield line method that accounts for momentum transfer and concrete rail deformation to determine barrier capacities. Also, the modified approach was used to examine bridge rails that have already been approved by the Federal Highway Administration or that have been crash tested in a controlled laboratory setting. Preliminary computer simulations were also carried out to corroborate the calculations of the modified yield line method by comparing the estimated internal energy of the deformed vehicle. The simulations demonstrated that the modified yield line method was accurate. In addition, applying the analysis to one bridge rail that was structurally inadequate in a crash test, it was shown that the current AASHTO design loads are appropriate, even for MASH impact conditions.
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