Modal Decomposition of Wind-Induced Lateral Displacements on a Steel Shear Frame

This paper presents a numerical procedure for investigating the dynamic behaviour of a planar steel frame subjected to turbulent wind loads. The main objective is to emphasize the modal distribution of top lateral displacements induced by time varying wind forces. Time histories of pressure and forces were acquired for a time period of 600 s from a Computational Fluid Dynamic (CFD) analysis. Air flow over rectangular bluff bodies was modelled in a bounded CFD domain in order to simulate wind’s stochastic behaviour in the presence of roughness. Simulated pressure in the CFD analysis is transferred as time-varying load applied on a steel shear frame. The studied structure is mathematically modelled as a dynamic multi-degree-of-freedom (MDOF) system directly related to its constituent stiffness, mass and damping matrices. Forced vibrations induced by highly arbitrary wind forces are dealt with Duhamel’s Integral to emphasise the modal decomposition of the overall lateral displacements response. Wind load function defined as a time-history of discrete force values requires the use of Simpson’s 1/3 Rule for numerical integration.