Analysis and Instrumentation of a Steel Bridge for Investigation of Superload Effects

Abstract

The number of superload trucks, which often carry loads three to 15 times those of common design vehicles, has increased in recent years. The increased frequency of occurrence has prompted concerns about the ability of highway bridges to accommodate such loads and remain in serviceable condition. To address these concerns, an analysis of effects of superloads has been conducted for a case study bridge. A detailed finite element (FE) model of the bridge, including all primary and secondary members, was created to evaluate the behavior. The FE analysis results were compared with results from a controlled load test of the bridge. The girder distribution factors determined experimentally and analytically were found to be significantly lower than comparable design values. Furthermore, from the load tests, the rotational restraint at the girder ends due to the abutments was determined to be as high as a fixed support. The FE model was then used to predict the effects of various superload trucks. The analysis results and field data suggest that some of the stiffener plates and cross-frame members of the analyzed bridge would be overstressed by certain superload truck configurations.