Dynamic response analysis of road vehicle–train–bridge coupled system for single-level rail-cum-road bridge under combined wind and wave actions

Cross-sea single-level rail-cum-road bridges are simultaneously subjected to traffic, strong winds, and waves, and their coupled vibration directly affects bridge serviceability and vehicle safety. To clarify the dynamic interaction mechanism of the wind–wave–road vehicle–train–bridge system, this study develops a refined time-varying coupled model using the Jinhai Bridge, the world’s first single-level rail-cum-road multi-tower cable-stayed bridge, as a case study. Road vehicles, trains, tracks, and the bridge are modeled as an integrated system through dynamic interaction matrices; wind tunnel tests are conducted to determine the aerodynamic coefficients of six typical vehicle models under the combined effects of the bridge and trains; and irregular wind and wave fields are simulated for multi-case dynamic analyses. The results show that the lateral vibration of the main girder is governed mainly by wind loads, whereas vertical and torsional vibrations are dominated by vehicle loads. Under the investigated cases, wave loading makes only a limited contribution to the response at the selected main-girder observation point. For the analyzed random-traffic realization, frequency proximity and unfavorable spatial coincidence among the train, a heavy truck, and the local bridge response produce a local amplification, indicating a potential bridge-mediated interaction mechanism; light vehicles are less affected. High train speeds may cause the windward wheel load reduction ratio to exceed the safety limit, whereas low train speeds can amplify bridge vibration and reduce road-vehicle safety and comfort.