Retrofit Railings for Narrow Through Truss and Other Obsolete Bridge Structures

摘要

Through truss structures are unique in that the superstructure of the bridge is exposed to impacts from errant vehicles. Effective bridge railings must not only exclude these vehicles from contacting the critical truss members by limiting system deflection, but must also prevent heavy vehicles from rolling over the barrier and contacting a truss member. Complete collapse of truss structures has resulted from automobile impacts as well as heavy vehicle impacts. Two bridge railing retrofit systems were systematically designed and developed in the project. The high performance system is designed to contain and limit vehicle roll of 20,000-lb (9000-kg) buses impacting at 55 mph (90 kmph) and a 15-deg angle. The low service retrofit system contains and redirects a 4500-lb (2000-kg) car impacting at 60 mph (95 kmph) and a 15-deg angle without endangering the truss members behind the retrofit system. Crash tests with vehicles ranging from the bus to an 1800-lb (800-kg) minicompact vehicle were used in the development and evaluation. Design drawings of the bridge rails, bridge attachment detail and approach rail are included in the report.