Development and Testing of an Optimized MASH TL-4 Concrete Bridge Rail
A new concrete bridge rail was developed and optimized using recently updated Manual for Assessing Safety Hardware (MASH) Test-Level 4 (TL-4) design loads. The rail was optimized to maximize vehicle stability, minimize installation costs, and mitigate the potential for deck damage by minimizing loads transferred to the deck. Additionally, the bridge rail was designed with a 39-in. installation height so that it would remain crashworthy after future roadway overlays up to 3 in. thick. The barrier had a front face with a 3-degree slope (i.e., batter) away from vertical to promote vehicle stability during impacts while also providing some slope to allow for slipforming real-world installations. Yield-line theory was utilized to design both interior and end regions of the barrier. Further, minimum deck strengths were determined and a deck overhang design procedure was provided for users desiring to modify their existing deck details. Finally, MASH test designation no. 4-12 was conducted on the new bridge rail to evaluate its safety performance as well as the potential for damage to the barrier and bridge deck. In test no. 4CBR-1, the 22,198-lb single-unit truck impacted the concrete bridge rail at a speed of 57.6 mph and an angle of 16 degrees. The single-unit truck was successfully contained and redirected, and all safety performance criteria were within acceptable limits as defined in MASH. Therefore, test no. 4CBR-1 was determined to be acceptable according to MASH test designation no. 4-12. Conclusions and recommendations for implementation were provided.
Highway Safety, Crash Test, Compliance Test, AASHTO, MASH 2016, Test Level 4, TL-4, Bridge Rail, Concrete Parapet, Bridge Deck, Deck Overhang, Cost-Optimization
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