Field Testing of Highway Bridges Enhanced by Assumptions of Composite Action

Abstract

A load rating procedure that involves field testing and composite action considerations for girders affected by external effects is presented in this paper. In the proposed procedure, the critical vehicle sequence for the bridge is determined and the actual response of the bridge is measured using a series of runs by driving a vehicle of calibrated weight. To replace the data readings affected by external effects, the position of the neutral axis corresponding to a fully composite action is assumed. After applying this correction, the actual load rating is discretized and compared with the analytical load rating so that different contributions to the loading capacity are quantified. A three-span non-composite steel girder highway bridge was used to illustrate the procedure. Results indicate that although the unintended composite action was the dominant contribution, the contribution was unreliable for loads beyond the linear elastic regime. It was observed that corrections made based on composite action assumptions improve the understanding of the case study because the contributions due to additional stiffness lateral and longitudinal distribution would have been unrealistic otherwise.