| In the marine environment,some coastal infrastructures,especially sea-crossing bridges,are easily affected by extreme weather such as typhoons and huge waves.At this time,sea-crossing bridges need to bear the coupling effect of wind,waves and undercurrent,which will affect the stability and safety of the bridge.Therefore,the research on the aerodynamic and hydrodynamics response of sea-crossing bridges subjected to wind-wave-undercurrent coupling is of great practical significance.Based on the two-phase flow theory,a three-dimensional computational fluid dynamics model of a sea-crossing bridge under the coupled effect of random wind-wave-undercurrent is established.The vortex dynamic characteristics,flow characteristics,aerodynamic response and the hydrodynamic pressure distribution of the bridge influenced by wind-only,wave-only,wind-wave and wind-wave-undercurrent coupling are comparatively studied.A fluid–structure separation solution method is implemented using Ansys–Midas co-simulation.From time and frequency domain perspectives,the displacement and acceleration responses of the sea-crossing Rail-cum-Road cable-stayed bridge influenced by wave-only,wind–wave,and wind–wave–undercurrent coupling are studied.Based on the analysis of the entire bridge dynamic response,the numerical model of the independent bridge tower is established.The fluid-solid coupling method is conducted to analyze the displacement and acceleration response of the independent bridge tower influenced by different parameters.The results are as follows:(1)Below the free surface,the water body will inhibit the vorticity development.Therefore,the vorticity caused by the wind-only is greater than the wind-wave-undercurrent coupling.Near the free surface,the influence of random wind on the vortex dynamics of the bridge gradually increases,causing the vorticity suddenly increases.Under the wind-wave-undercurrent coupling,the wind field will have a boosting effect on the wave field,which caused the impact load of the bridge tower below the water-air interface is greater than that of the upper bridge tower.Near the still water surface,the influence of random wind on the pressure of the bridge gradually increases,causing the average pressure of wind-wave-undercurrent coupling is greater than the wave-only and wind-wave coupling.The closer to the water surface,the greater the increase of the average pressure,and the greater the impact of the wind-wave-undercurrent coupling.(2)The dominant frequency under wind–wave–undercurrent coupling is close to the natural vibration frequencies of several bridge modes,such that wind–wave–undercurrent coupling is more likely to cause a resonance effect in the bridge.Compared with the wave-only and wind–wave coupling,wind–wave–undercurrent coupling can excite bridges to produce larger displacement and acceleration responses:at the middle of the main girder span,compared with the wave-only case,the maximum displacement in the transverse bridge direction increases by 23.58%and 46.95%under wind–wave and wind–wave–undercurrent coupling,respectively;at the tower top,the variation in the amplitude of the displacement and acceleration responses of wind–wave and wind–wave–undercurrent coupling are larger than those in the wave-only case,where the acceleration change amplitude of the tower top is between-0.93 and 0.86 m/s~2 under the wave-only case,-2.2–2.1 m/s~2 under wind–wave coupling,and-2.6–2.65 m/s~2 under wind–wave–undercurrent coupling,indicating that the tower top is mainly affected by wind loads,but wave and undercurrent loads cannot be neglected.(3)As the wind speed increases from 20m/s to 40m/s,the maximum displacement difference between the front and back bearing platform is:101.85%,125.89%,132.27%,149.47%,154.78%,indicating that the greater wind speed will lead to the greater displacement difference.The displacement response of the upper beam is greater than the lower beam,but the displacement response is less than the tower top.The changes in the displacement response of the three positions are increased as the wind speed increases,which shows that the impact of wind speed on the upper structure of the bridge is significant.The deeper underwater,the smaller the bridge tower is affected by the wind speed change and the smaller the displacement near the water-air interface.The displacement response of the upper beam and the tower top will increase as the wave height increases.Near the water-air interface,the higher the wave height,the lower the displacement response.Different undercurrent velocities have little effect on the dynamic response of the substructure,but still have some influence on the superstructure of the tower. |
