Experimental Study on the Dynamic Response Characteristics of the Floating Bridge Considering Pontoon Failure Under the Combined Action of Earthquakes and Waves

This study experimentally investigates the dynamic characteristics of an end-anchored floating bridge (FB) under the combined action of earthquakes and waves, considering the pontoon failure. Focusing on the peak ground acceleration (PGA) of earthquakes, wave periods, and wave heights, the multidimensional dynamic response of different bridge girder locations was analyzed under earthquakes, pure waves, and earthquake-wave conditions. Experimental results show that pontoon failure changes the dynamic behavior of the FB, significantly increasing sway amplitude under intense seismic action with high PGA. In contrast, heave motion is strongly constrained in the vertical direction, with notable amplitude increases occurring only at the damaged pontoon and adjacent girders, while its influence remains limited in distant regions. Rotational responses exhibit varying sensitivities to seismic and wave effects: Roll motion is more susceptible to amplification under external excitations, whereas yaw motion remains insensitive to all loading conditions. Under combined earthquake-wave action, the dynamic response of the bridge shows a strong dependence on wave height. In low-wave-height conditions, pontoon failure amplifies heave and roll displacements, increasing the risk of structural damage. In high-wave-height conditions, the displacement trends after pontoon failure closely resemble those observed under pure wave action.