Time-varying up-crossing theory-based non-stationary extreme estimation of gust-loading on rectangular cylinder due to thunderstorm-like wind

Abstract

An active wind tunnel test was conducted to experimentally investigate the nonstationary time-varying extreme characteristics of the aerodynamic force on a 5:1 rectangular cylinder under a thunderstorm-like gust. Previous studies have primarily estimated the time-varying extremes of nonstationary surface wind pressure under the assumption of a nonstationary, uniformly modulated stochastic process. This study employed the time-varying upcrossing theory to precisely calculate the time-varying extreme values and peak factors of transient loads on a 5:1 rectangular cylinder subjected to a thunderstorm-like wind. The findings revealed that the wind pressures and aerodynamic lifts of a rectangular cylinder subjected to thunderstorm-like gusts present distinct time-varying and non-stationary features The extreme value distribution (probability density function and cumulative distribution function) estimated by applying the time-varying upcrossing theory also demonstrates significant temporal evolution. Accordingly, utilizing conventional stationary stochastic process estimation methods may generate considerable disparities. A comparison of the findings derived from the theory proposed in this work with those under the uniform modulation assumption suggests that the latter leads to an underestimation of the extreme values of the actual wind load.