Directional effects of correlated wind and waves on the dynamic response of long-span sea-crossing bridges

Sea-crossing bridges are sensitive to wind and wave loads, different wind and wave loading directions will lead to significant differences in bridge dynamic performance. The design of such a structure may benefit from considering the directional characteristics of loading. This study thus proposes a directional wind-wave-bridge (DWWB) numerical framework by incorporating multivariate statistical dependence, directionality analysis, and a wind-wave-bridge system for sea-crossing bridges. The trivariate joint probability distribution is first simulated by an optimized C-vine copula, and the correlated wind and wave combinations are identified by the 3D environmental contours based on the measured data in the bridge site. Directionality analysis involving the alignment and misalignment of wind and waves are further investigated. The proposed approach is finally applied to a real sea-crossing bridge with the mean wind speed, significant wave height, peak wave period, wind direction, and wave direction as the input variables of DWWB. The nonlinear dynamic response as the output is solved by equilibrium iterations using the Newmark-beta method. The results show that the occurrence probability of wind-wave misalignment is up to 50%. The dynamic response of the bridge is sensitive to the wind and wave direction. Neglecting the multivariate statistical dependence and directional effect of wind and waves may lead to a conservative and unrealistic result.