Full scale testing of old steel truss bridge

Abstract

As part of an investigation to comprehend behavior of old steel truss bridges, ultimate load tests were carried out on a steel truss bridge that was transported to the structural laboratory. The first ultimate load test consisted of testing the bridge in its existing configuration without any retrofit. The failure mode was by sudden rupture of a forged diagonal tension member. The mode of failure was ‘brittle’ in nature and there was no warning. The failed member, together with other forged tension members, was retrofitted and an additional ultimate load test was conducted. The retrofitted bridge failed in a more ductile manner. The failure took place gradually and there was ample warning before the failure. A major conclusion from ultimate load tests was that in inspecting old steel truss bridges one should pay very close attention to tension members that use forging. This paper presents a brief overview of the ultimate load tests conducted. More detailed information on the complete scope of the project is presented in Azizinamini et al., Final report, STPB-STWD(13), (1997); 479 pp.