Study On The Buffeting Response Of Longspan Bridge Under The Action Of Completely Nonstationary Wind Field

As the span of the bridge continues to increase,the problem of structural wind-induced vibration is becoming more prominent.Unlike other forms of vibration,buffeting is a kind of forced vibration,which originates from the wind fluctuations speed acting on the flexible structure,buffeting will inevitably occur as long as any flexible structure is in the natural wind field.The amplitude of the buffeting depends on the size of the wind speed,the stiffness of the structure,wind speed coherence function,etc.Especially for bridges with a large span,long periods of buffeting can affect the stability of bridges.And in serious cases,it can lead to structural system damage,so the calculation of buffeting response is essential.In nature,there are many destructive transient extreme winds(such as typhoon,tornado,thunderstorm,etc.),showing strong nonstationary characteristics.Therefore,in the study of random vibration,these extreme winds cannot be simulated by the commonly used stationary random vibration model,which is usually described as a nonstationary random process.Compared with stationary wind speed,these extreme wind events pose a greater threat to the safety of flexible structures,so it is particularly important to accurately analysis the nonstationary response of structures under extreme winds.Based on a completely nonstationary wind field,this paper carries out the time domain buffeting analysis of the long-span cable-stayed bridge.The main research contents are as follows:(1)According to the power spectrum density and coherence function recommended by the specification,the evolutionary power spectrum model and time-variant coherent function model of the non-stationary wind field are modulated by modulation function.This paper introduces the theory of nonstationary strength and weakness measurement based on the measured data,determines and compares the non-stationary strength of the two groups of measured winds,and uses the Priestley method to estimate the evolutionary power spectrum and coherence function of the two groups of measured winds.(2)Based on the POD interpolation enhancement method,the wind speed time histories of the main beam and bridge tower of Su-Tong Yangtze River Highway Bridge is simulated with the assistance of MATLAB software.It is pointed out that in the wind field,the simulation with spectral representation(classic phase formula)is not scrupulous.It may affect the accuracy of simulation results,and even resulting in errors in simulation results.Then,numerical examples demonstrate that the error caused by its expression,and its expression is improved.(3)The self-excitation force is expressed in the time domain with the Roger rational function,and then the buffeting response is solved based on the Newmark-β method,and the influence of time-varying mean wind speed,strong and weak nonstationary evolutionary power spectrum of fluctuating wind and time-invariant and time-varying coherence functions on the buffeting response of the long-span cable-stayed bridge.