Development of a Bridge Railing Optimized for Rural,Low-Volume Roads

Abstract

A new steel bridge rail was developed for use on rural, low-volume bridges. The railing consisted of 31-in. tall, 12-gauge W-beam guardrail mounted on S3x5.7 posts, which were supported by steel square-tube sockets. These side-mounted sockets were attached to the deck edge using a unique bolted design that connects directly to coupling nuts and threaded anchor rods embedded into the bridge deck. Thus, during a crash, the tensile impact loads are transferred directly to the anchor rods and the risk of damage to the deck edge is minimized. Full-scale crash testing was conducted according to test 2 to 11 of the AASHTO’s Manual for Assessing Safety Hardware (MASH). The test vehicle struck the bridge rail at 44.2 mph and an angle of 25.5° and was successfully contained and redirected. Damage to the bridge rail consisted of bent posts and deformed guardrail. No damage to the deck or sockets was observed. The tests passed all evaluation criteria of MASH test 2 to 11. The new railing was deemed crashworthy to MASH Test Level 2 (TL-2) with a post spacing of 75 in. Additionally, when the post spacing is reduced to 37.5 in., the railing was determined to be MASH Test Level 3 (TL-3) crashworthy through a comparison to similar, crash-tested, W-beam guardrail systems. BARRIER VII simulations showed that the new railing could be directly connected to the Midwest Guardrail System without a transition. Guidance was provided pertaining to the length of guardrail required adjacent to the bridge rail.