Development of Low-Cost, Energy-Absorbing Bridge Rail

A new, low-cost bridge railing was designed to be compatible with the Midwest Guardrail System (MGS). The barrier system was configured to reduce bridge deck width and its associated cost. Several concepts for an energy-absorbing bridge post were developed and tested; the concepts included strong-post designs with plastic hinges and weak-post designs with bending near the bridge deck attachment. The final railing concept incorporated S3 × 5.7 (S76 × 8.5) steel posts housed in a tubular bracket placed at the outside vertical edge of the deck and anchored to its top and bottom with one through-deck bolt. The W-beam rail section was attached to the posts with a bolt that was designed to fracture during an impact event. Two full-scale crash tests were performed in accordance with the Test Level 3 impact conditions provided in the Manual for Assessing Safety Hardware. The bridge rail system met all safety performance criteria for both the small car and pickup truck crash tests. Barrier VII computer simulations, in combination with the full-scale crash testing programs for the bridge railing and MGS, demonstrated that a special-approach guardrail transition was unnecessary.