Experimental study on the dynamic responses and wind-wave coupling effects of a side-anchored floating bridge

This study proposes a modal-dominated truncation method and experimentally investigates the dynamic responses of a side-anchored floating bridge (SAFB) under the combined action of wind and waves. A full-scale numerical model was first used to identify the key modal contribution region and determine the representative truncated segment. The boundary stiffness at the truncated ends was then calibrated by matching the target modal periods of the full-scale model. A 1:70-scale physical model was fabricated and validated through free decay tests and modal comparisons. To evaluate the structural motions and mooring tensions, model tests of the SAFB under wind-only, wave-only, and combined wind-wave conditions were conducted. Results demonstrate that the proposed truncation method effectively reproduces the target dynamic characteristics of the full-scale bridge. Under wind-only conditions, the mooring system significantly suppresses local sway and heave responses near the moored pontoon, with its heave amplitude 8%–51% lower than that of the unmoored pontoon. However, this restraining effect is relatively limited under wave actions. Under combined conditions, transverse wind mainly influences the mean response, while waves dominate the response standard deviation. Above the transition wind velocity, enhanced coupling between wind-induced low-frequency motion and wave-frequency oscillations markedly amplifies the sway and heave responses.