Definition and Derivation of Windstorm-Intensity Indicator to Evaluate Wind-Induced Structural Elastoplastic Responses

To select the most unfavorable storm to conduct probabilistic wind hazard analysis for the probability evaluation of wind-induced structural elastoplastic responses, this study defines the storm intensity indicator as a measure of relative amount of wind-induced structural damages using the hysteretic energy–based structural damage evaluation criterion, which can comprehensively reflect the potential destructiveness to structures by the maximum mean wind speed, duration, and time histories of the storm. Based on structural dynamics and several assumptions, relationships among the damping, hysteretic, and load input energy of elastic and elastoplastic structures were established, and the hysteretic energy of the elastoplastic structure is expressed as a function of the wind load input energy of the damped elastic structure with the same initial stiffness using an equivalent undamped elastic structure. The analytical calculation formula of the input energy of the damped elastic structure was derived, and the simplified calculation formula of the storm intensity indicator is expressed as a function of time-varying mean wind speeds of a storm. The rationality of various assumptions during the derivation was verified. A case study of one steel frame was conducted to show advantages of the storm intensity indicator. The results show that the storm intensity indicator can be used effectively to select the most unfavorable storm for the probability evaluation of wind-induced structural elastoplastic responses, and can significantly improve computational efficiency compared with the time history analysis method.