The recent multiple fatality anhydrous ammonia truck-bridge rail accident in Houston, Texas, and the school bus-bridge rail accident near Martinez, California, emphasizes the need for a bridge rail to contain heavy trucks and buses. Present bridge rails are only designed to restrain and redirect passenger cars up to 4500 lb (2041 kg) in weight traveling 60 mph (97 kph) and impacting the rail at a 25 deg angle. The current bridge rails must be at least 27 in. (69 cm) high and be able to resist a static load of 10,000 lb (4536 kg) without exceeding a specified allowable working stress based on an elastic analysis. Bridge rails designed in accordance with the present criteria have in general performed well in restraining passenger cars. Recent truck and Concrete Median Barrier (CMB) crash tests have indicated that some of our traffic rails designed by the present criteria have considerable reserve strength and are capable of redirecting heavy buses and trucks. The objective of the report is to present an analytical evaluation of the capabilities of six standard Texas bridge rails to contain automobiles, buses and trucks. This evaluation consisted of an analysis of the strength of the bridge rails to determine if they were strong enough to resist the impact forces. In addition, an analysis was made to determine if they are high enough to prevent high center-of-gravity buses and trucks from rolling over the rails.
Abstract