Vibration response analysis of simply supported girder bridges using millimeter-wave radar measurements

To address the shortcomings of dynamic evaluation methods for simply supported girder bridges under moving loads, as well as the inefficiencies of traditional dynamic load test measurements, which are time-consuming and labor-intensive, this paper proposes a dynamic evaluation method incorporating the contact surface effect of actual wheels. This method refines a vehicle-bridge coupling model and verifies its accuracy through dynamic displacement measurements using millimeter-wave radar, complemented by modal analysis and dynamic load testing. The method also accounts for the effects of bridge deck roughness, vehicle speed, and weight on the impact coefficient of the bridge, comparing these effects with those outlined in the current code. The practical application of this method demonstrates that millimeter-wave radar, as a novel non-contact testing approach, can accurately measure the complex vibrations of bridges. The multi-point contact model predicts vehicle-bridge interactions more precisely than the single-point contact model, particularly under poor bridge deck conditions, with discrepancies between the models reaching up to 9.59% on Class D bridge deck roughness. The current code, which calculates the impact coefficient considering only a single factor, may not accurately reflect the actual impact coefficient of the bridge. In this study, an impact coefficient regression formula is also derived using vehicle speed and bridge deck roughness as independent variables, offering a tool for estimating the impact coefficients of similar bridges.