Proof Load Testing of Deteriorated Steel Girder Bridges

Proof load tests were carried out on three deteriorated steel girder bridges with simple supports. Selected bridges are more than 60 years old, and their span lengths range from 11.0 to 15.5 m. Two military tanks were used to load the bridges up to a predetermined proof load level, which depended on the maximum allowable legal load. The midspan moment was increased in several steps by gradually moving the tanks closer to the midspan. Each tank weighed over 530 kN. Stresses and deflections in steel girders were measured at selected locations. Small stresses and a linear response were considered as the indication of a safety reserve. All bridges were able to sustain the applied proof load. Observed stresses and displacements were considerably smaller compared with those from analytical models. The composite action between concrete slab and steel girders was observed even at the maximum load level, although no shear connectors were provided. Nonstructural members such as parapets, railings, and concrete facade were also contributing to the flexural stiffness. For all bridges, the bearings provided partial restraint to the rotation at supports.