大跨度桥梁主梁节段模型非平稳抖振时域模拟与分析

Time-domain simulation and analysis of nonstationary buffeting responses of girder section model of a long-span bridge

针对台风非平稳性显著的特征,开展大跨度桥梁主梁节段模型非平稳抖振时域模拟与分析。基于准定常理论,拓展了桥梁非平稳气动力模型,并通过阶跃函数进行了非平稳自激力的时域化。在此基础上,采用谐波合成法模拟了台风非平稳脉动风场,从而进一步开展了主梁节段模型的非平稳抖振响应时域分析,并与平稳理论分析结果进行了对比。研究结果表明:非平稳气动自激力可采用二维阶跃函数法进行时域化,并通过时变平均风速反映流体记忆效应的强度;桥梁非平稳静风位移与抖振位移RMS值均明显大于平稳抖振分析结果。因此,台风作用下大跨度桥梁的抖振响应分析有必要充分考虑非平稳特征的影响。

In allusion to the obvious nonstationary features observed in typhoon winds,a time-domain simulation and analysis on nonstationary buffeting responses of the girder section model is conducted for a long-span bridge.The aerodynamic force model is extended in a nonstationary perspective based on the quasi-steady theory,and the nonstationary self-excited forces are represented in a time-domain form using the indicial function.On this basis,the nonstationary fluctuating wind field of typhoon winds is simulated via the spectral representation method.A time-domain buffeting analysis on the section model of a long-span bridge is further conducted,and the results are compared with those from a stationary perspective.The analytical results indicate that nonstationary self-excited forces can be successfully represented in time domain using the two-dimensional indicial function,and the strength of the fluid memory effect can be reflected by the time-varying mean wind velocity.The nonstationary aerostatic displacement as well as the RMS of buffeting displacement is obviously larger than the stationary result.Hence,the nonstationary features existing in typhoon winds are essential to be considered in the nonstationary buffeting analysis of long-span bridges under typhoon actions.