Time-domain Based Simulation For Nonstationary Wind Speed At Bridge Deck

Wind load is one of the key factors to control the design and operation of long-span bridges and other buildings.There are often non-stationary characteristics of wind speed in mountainous terrain.Therefore,it is necessary to analyze the non-stationary wind induced response of the long-span bridge structure.At present,wind response analysis of bridge structures is mainly carried out in two major categories: frequency and time domain.When the bridge structure is nonlinear or aerodynamic nonlinearity,the frequency domain method that can only perform linear or linear analysis of the structure is not applicable.At this time,the time-domain method that can perform nonlinear analysis should be selected,that is,the wind-induced response time-history analysis of the bridge structure.The premise of the response time history analysis of bridge structure is to obtain the wind speed time series that act on the bridge,which is,to simulate the wind speed field based on the time domain method.Based on the time-domain method,this paper proposes the improvement and innovation of the non-stationary wind field simulation method.The specific research work is as follows:(1)In this paper,the accuracy and simulation efficiency of the simulation based on VAR model and classical spectral representation on wind speed field are compared.It is found that the simulation accuracy based on spectral representation is higher than the simulation method based on VAR model,and the simulation efficiency based on VAR model is much higher than based on spectral representation.The simulation samples based on the VAR model also meet certain accuracy requirements.When the actual engineering requirements for simulation accuracy are not particularly high,and the simulation wind speed points are particularly large,it is accurate and efficient to select VAR model to simulate the wind speed field.(2)After introducing the time-varying modulation function,the non-stationary wind speed field is simulated using the time-varying vector autoregressive(TVAR)model.Through the observation and analysis of the simulation sample and the comparison of the autocorrelation and cross-correlation functions and the objective correlation functions of the multiple simulation sample estimation,it can be concluded that the simulation of the non-stationary wind field based on TVAR model is effective and feasible.At the same time,compared with the nonstationary wind field simulation based on spectral representation,the conclusion that the nonstationary wind field simulation based on TVAR model is more efficient is obtained.(3)This paper simulates a wind speed field such as thunderstorm wind with time-varying variance characteristics based on univariate GARCH model.Through the simulation of the univariate GARCH model,the obtained simulation samples not only maintain a non-stationary trend,but also maintain heteroscedasticity.The simulation of the traditional linear filtering method has been improved.(4)In this paper,a multivariate GARCH model is simulated for wind speed fields with time-varying variance characteristics such as thunderstorms.Through the simulation of multivariate GARCH model,the obtained simulation samples not only maintain heteroscedasticity,but also maintain the time-varying correlation between multiple samples,which is effective and feasible for the simulation of wind speed field with multiple simulation points.It has certain engineering application value.