Characteristics Of Wind Loads On Spherical Shells With Large Rise-span Ratio

As a representative large-span space structure, spherical shells are more widely used among public structures, such as roofs of stadiums, exhibition halls, etc. Wind loads are a significant proportion of the total load acting on spherical shells, and so the magnitude and distribution of the resultant pressures must be considered. Previous studies of spherical shells mostly focus on shells with rise-span ratio less than 1/2, and little research aims at spherical shells with rise-span ratio more than 1/2. Because of the complexity of wind loads on spherical shells, and the pressure distribution is significantly correlated with Reynolds numbers, the height of the base, etc. The load code of building structures can't satisfy the design in most cases, therefore wind tunnel test are needed to obtain necessary information of loads. Based on the detailed results of wind pressure from a wind tunnel test on a rigid spherical model with 3/4 rise-span ratio, the characteristics of the mean and fluctuating wind loads acting on the surface of the spherical shells and the flow around the shells are systematically investigated. The models of auto-spectrum and cross-spectrum are also proposed. The main research contents were presented as following:1. The distortion effects introduced by pressure tubing systems in measurements of fluctuating pressure are discussed meticulously, and study the main parameters effect on the tubing transfer function. The transfer function of the tubing systems is obtained by theoretical analysis and experiment. In the end, the distortion signal of wind tunnel test is corrected using the known tubing transfer function.2. Based on the detailed results of wind pressure from a wind tunnel test on a rigid spherical model with 3/4 rise-span ratio, the characteristics of pressure distributions on the surface and the effects of Reynolds numbers, the height of the base on pressure distributions of the shell are investigated. The characteristics of pressure distributions of spherical shells with different rise-span ratio are also discussed by Computational Fluid Dynamic(CFD) numerical simulations techniques. Finally, a static wind load model is proposed to describe wind loading acting on spherical shells in mechanics analysis using the finite element method.3. Based on the analysis of spectral characteristics such as spectral shape, position of the spectral amplitude, spectral attenuation slope, etc, the model of auto-spectrum is proposed using AR model of modern spectral estimation. Then, coherence functions between typical taps along the span are discussed on the surface of the spherical shell. Consequently, the spatial correlation along span is investigated in frequency domain. Further more, the cross-spectral attenuation coefficients in different zones of the spherical shell and the model of cross-spectrum are proposed.