Nonstationary time-varying extreme value of downburst-induced wind loads based on transformed stationary method

Abstract

Downbursts exhibit pronounced transient effects and nonstationary characteristics. Herein, a pressure measurement test of a rigid segment model under a downburst-like wind is conducted on a 5:1 rectangular cylinder using a multi-fan active control wind tunnel. Based on the experimental results, downburst-like wind field and wind load characteristics are studied. The results show that the downburst-like wind, wind loads and evolution power spectrum density(EPSD) have prominent time evolution features, transient effects, and nonstationary time-varying characteristics. Subsequently, based on the generalized extreme value (GEV) distribution theory, the time-varying extreme values of the nonstationary random processes under the uniform modulation approximation are estimated, and the corresponding peak factors are given. The fitting accuracy of the generalized extreme value distribution is found to be good. The calculated peak factors of the wind pressure and overall aerodynamic lift are higher than those of the wind speed. Owing to flow separation, the peak factor of the pressure coefficients on the windward surface is smaller than those on the top and leeward surfaces. The peak factors in the flow separation and wake regions of the top surface are larger than those in the reattachment region.