Development Of A Low Profile Bridge Rail For Test Level 2 Applications PDF Download

Bridge railings are a safety feature to protect the traveling public by containing and redirecting errant vehicles during run-off-road (ROR) events. Most bridge railing design and evaluation efforts have focused on ROR crashes on high-volume roads. Bridge railings for low-volume roads can be designed for lower impact speeds, so railings designed for high-volume roads are unnecessarily robust for low-volume applications and can be optimized to reduce costs for bridge owners while still providing adequate safety. The aim of this research has been focused on improving the design of two low-volume bridge railing systems for use by the United States Department of Agriculture, Forest Service, Missoula Technology and Development (USDA-FS-MTDD) The first modified barrier system was originally a low-height reinforced concrete barrier designed for National Cooperative Highway Research Program Report No. 350, Test Level 2 standards (NCHRP 350 TL-2). In this research, the barrier was redesigned and optimized to meet Manual for Assessing Safety Hardware (MASH) TL-1 requirements by reducing railing dimensions and reinforcement. Additionally, construction guidance was developed for installation on concrete bridge decks of various thicknesses and overhang widths. AASHTO LRFD Bridge Design Specifications were utilized to evaluate crashworthiness and structural adequacy of the modified barrier design and the deck’s structural adequacy for lateral impact loads, vertical loads of vehicles leaning on the top of the barrier during impact events, and design traffic loads traveling adjacent to the barrier in routine service. The second bridge deck and rail system featured a transverse nail-laminated deck with a low-height timber bridge rail mounted at the edge of the deck. The original deck with railing was crashworthy, but the deck was associated with higher labor costs and more susceptible to deterioration. Further, the agency desired it be used on transverse glulam timber decks. Thus, a study was begun to adapt the railing system for use on transverse glulam decks, which would also increase the durability and likely lower the onsite construction time and labor cost of the deck system. Component tests were performed on the original and modified deck systems to confirm the acceptable performance of the modified system. From the component testing results, the glulam rail and scupper blocks installed on a transverse glulam deck resisted more lateral force, absorbed more energy, and had higher initial linear stiffness as compared to the same rail and scupper blocks installed on a transverse nail-laminated deck. Thus, the low-height, glulam timber bridge railing installed on a transverse, glulam deck will provide equal or greater safety performance as compared to the same bridge rail installed on a transverse, nail-laminated deck. As a result, the low-height, glulam timber bridge rail installed on a transverse glulam deck has also been deemed adequate for use in MASH TL-1 applications.