Method and sensor for monitoring weight of trucks in motion based on bridge girder end rotations

Abstract

Traffic monitoring, including the estimation of axle and gross vehicle weights of passing trucks over bridges plays an important role in the determination of actual service loads. Knowledge of these loads aides in the development of appropriate maintenance plans and enforcement of weight limits on bridges. Bridge weigh in motion (BWIM) technology uses bridges as a scale to measure truck weights and speeds. The research reported in this article pertains to the development of a new BWIM system based on the monitoring of girder rotations at the bridge abutments. The measured end rotations are directly related to the axle loads by means of influence lines. The changes in girder rotations at the abutments are measured by a fibre optic rotation sensor, specifically designed for the proposed BWIM system. The rotation sensors are then incorporated into the BWIM system for correlation of the axle weights to the end span rotations. The applicability and accuracy of the proposed system was examined by tests on a four-span steel girder bridge. The field implementation included calibration and validation of the system with trucks pre-weighed at a nearby weigh station.