Nonstationary Turbulent Wind Speed Models and Their Effects on Wind-Induced Responses of Tall Buildings

Abstract

There exist so many approaches to extract the time-varying mean (TVM) of nonstationary wind speeds under the nonstationary wind speed model, such as the wavelet transform and empirical model decomposition. These approaches yield different fluctuating wind components, resulting in significant differences in related wind parameters of fluctuating wind speeds (e.g., turbulence intensity, turbulence integral length scale, and wind spectrum). Meanwhile, compared to the stationary wind speed model, the nonstationary wind speed model would lead to different predictions of wind loads and wind-induced responses of a tall building even under the same wind field. This paper first derives the theoretical relationships of statistical parameters between stationary and nonstationary wind speed models, including turbulence intensity, turbulence integral length scale, and turbulence wind spectrum across different models. Wind speed data recorded during Typhoon Mangkhut from September 15 to September 18, 2018, are analyzed to validate the derived relationships. The analysis results confirm that the turbulence intensities and turbulence integral length scales of fluctuating wind speed components under the nonstationary wind speed model are generally smaller than those under the stationary wind speed model. The response analyses of an actual tall building were conducted under Typhoon Mangkhut utilizing various wind speed models. Significant disparities in structural responses are observed between the simulated stationary and nonstationary wind conditions. This result indicates that for typhoon wind fields with noticeable nonstationary properties, the conventional stationary wind speed models may not adequately capture the full dynamic wind effects on tall buildings. Besides, improper extraction of the TVM and subsequent simulation of the nonstationary wind velocity field can lead to substantial discrepancies between the calculated structural responses and the true values. It is thus necessary to establish a nonstationary wind speed model with a proper TVM for the wind-resistant design of tall buildings under typhoons or other nonsynoptic wind environments.