Elastic Wind Spectra for the Design of Slender Structures

Traditional wind design often relies on simplified static load assumptions, which fail to capture the dynamic nature of wind loading. The distribution of wind loads and the estimation of the gust factor (structural factor, c<inf>s</inf> c<inf>d</inf>, in EN 1991-1-4) are largely based on this simplified gust loading approach, considering only the fundamental mode of vibration. This study uses a linear continuum model to accurately quantify the dynamic effects of wind on high-rise buildings with height-to-breadth-to-depth ratios of 3-1-1, 4-1-1, and 5-1-1. To solve this dynamic problem, we formulate the equation of motion for the continuous system under wind excitation, evaluate vibration modes and frequencies, and perform modal analysis of the forced dynamic response in the time domain. Random wind histories at various heights are generated from existing wind tunnel data using Monte Carlo simulations. We then analyse engineering demand parameters (EDPs) such as deformations, accelerations, shear forces, and overturning moments. From these EDPs we construct elastic wind response spectra, which effectively illustrate the relationship between building vibration properties and critical wind demand parameters. The comparison of these spectra to code demands reveals a potential need to reduce prescribed pressure coefficients for slender structures, revise the existing response procedures in EN 1991-1-4, and integrate available local aerodynamic data in wind design.