The Effect of Truck Loads on Highway Bridges via Bridge Weigh in Motion Algorithm

Traffic loads on highway bridges have been increasing in the past years. It is necessary to quantify the actual truck axle configurations and weights for monitoring the live load and its effect on the bridge conditions. Bridge Weigh in Motion (B-WIM) systems typically employ instrumentation installed on the bridge to measure the speed, axle configurations and weight of crossing trucks. Instrumentation should also be included to measure critical strains, distortions and accelerations due to both the static and dynamic effects of any truck crossing a bridge. Once truck live loads and the corresponding critical bridge responses are identified, it should be possible to correlate and interpret this data to estimate whether continued truck crossings are causing significant changes in the lifecycle of a bridge. A prestressed concrete highway bridge was instrumented with both a bridge monitoring system and a pavement weigh-in-motion system. The structure was identified, and a finite element model was calibrated to allow B-WIM and bridge vehicle interaction analysis. The authors implemented the traditional Moses’s static B-WIM algorithm with the influence line generated from the calibrated model. The example illustrates the challenges and limitations of such approach.