Discussion of unsteady aerodynamic force acting on a large-span flat roof structure

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Publication year 2017
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Title Discussion of unsteady aerodynamic force acting on a large-span flat roof structure
Author Yuki Takadate, Yasushi Uematsu
Summary The present paper discusses the unsteady aerodynamic forces acting on a large-span flat roof based on a CFD (Computational Fluid Dynamics) analysis with LES (Large Eddy Simulation). First, mean wind pressures and RMS fluctuating wind pressures are computed in a smooth uniform flow with four kinds of domain size and grid divisions. Based on the results, the most appropriate computational domain and mesh division are made clear. Then, the distributions of mean wind pressure coefficients and RMS fluctuating pressure coefficients on a rigid flat roof are investigated both in the smooth uniform flow and the turbulent flow. Next, a forced vibration test is carried out, in which the roof is vibrated in the first anti-symmetric mode. In the simulation in the smooth uniform flow, the vibrating amplitude and frequencies are varied over a wide range to understand the characteristics of the wind pressure acting on the roof and the influence of roof vibration on the aerodynamic forces, represented by the aerodynamic stiffness and damping. The simulations in the turbulent flow are also carried out for some typical amplitudes and frequencies. Based on the result, the aerodynamic stiffness and coefficients at the location of anti-node vibration are computed.
These results are compared to the previous experimental results. Finally, the dynamic behavior of large span flat roof is investigated using the aerodynamic stiffness and damping coefficients predicted from the results of the forced vibration test. The results indicate that the natural frequency and density of the roof are important for evaluating the dynamic response. In addition, we should focus on the dynamic response of roof surface in low wind speed range for future works.