Unsteady aerodynamic characteristics of long-span roofs under forced excitation

Wind-induced vibration is significant for light and flexible structures, and aerodynamic effect has to be considered in the estimation of wind load and dynamic response of these structures. The unsteady aerodynamic characteristics of long-span roofs are investigated numerically in this paper using Large Eddy Simulation. Roofs under forced excitation are simulated, and the distributions of aerodynamic coefficients on rigid and vibrating roofs are estimated. The computed coefficients show good agreement with the experimental results. The influences of inflow turbulence, shape of roof and other parameters on the aerodynamic coefficients are also analyzed. It is found that the mean wind pressure coefficients mainly depend on the vortex shedding and reattachment positions. These coefficients in the cases studied remain almost the same with increasing excitation frequency, while the fluctuating pressure coefficients and unsteady aerodynamic coefficients change with frequency regularly. The probability density functions of wind pressure on the vibrating roofs show obvious non-Gaussian characteristics, and the wind pressure spectra exhibit peaks at the excitation frequencies. The dynamic response of long-span roof is then predicted using the mechanical admittance function. Results show that the displacement response of the structure will be under-estimated without considering the unsteady aerodynamic effect especially for flexible structures.