Development and Testing of a Test Level 4 Concrete Bridge Rail and Deck Overhang

Abstract

A Manual for Assessing Safety Hardware (MASH)-compliant Test Level 4 (TL-4) concrete bridge rail was optimized to satisfy MASH TL-4 design loads, maximize vehicle stability, minimize installation costs, and mitigate the potential for deck damage by minimizing loads transfer 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 from vertical to promote vehicle stability during impacts while also providing some slope to allow for slipforming 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 4-12 was conducted on the new bridge rail to evaluate its safety performance criteria, damage to the barrier and a critical deck configuration, and its working width. In test 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 4CBR-1 was determined to be acceptable according to MASH Test 4-12. Conclusions and recommendations for implementation are provided.