Studies On Properties Of Fluctuating Wind And Wind-Induced Response Computing Methods Of Long-Span Roofs

In recent years, with the development of modern building materials and construction techniques, many long-span roof structures with beautiful shapes have been widely constructed as large public buildings such as airport terminals, stadiums, theatres and so on. These structures are light, flexible and they also possess small damping factor and low vibration frequencies. Therefore wind load becomes one of the main loads in structural design. But the theory of wind-induced vibration response computing methods has not been well developed yet. Based on previous studies, researches on properties of fluctuating wind and wind-induced vibration response computing methods of long-span roof structures are carried out in this thesis.Firstly, based on wind pressure data measured on the rigid model in the wind tunnel, the properties of fluctuating wind on long-span roof structures are studied. And it is pointed out that the empirical equations of the fluctuating wind speed spectrums and coherent functions are not suitable for long-span roofs. It will lead to obvious errors if the quasi-steady resumption is used to compute wind-induced vibration response of long-span roof structures. At the same time, the nondimensional spectrum of the fluctuating wind pressure is fitted. And preliminary study of the non-steady computing method of wind-induced vibration response is carried out.The mode contribution factor and the cumulate mode contribution factor are proposed to identify the mode which contributes greatly to the wind-induced vibration response and judge the reasonability of the computing modes. The distribution of mode contribution factor of latticed shell structures with different forms, different spans, and different span-height ratios is analyzed. The analysis shows that the order of the fundamental mode which makes the greatest contribution to wind-induced vibration response of single-layer lattice shell is high and the order of the fundamental mode of double-layer shell is low. Ritz-vector method is used in computing of wind-induced vibration response of these long-span structures whose order of fundamental mode is high in the mode series. And the precision and validity of this method are also analyzed and verified in the examples. Finally the thesis uses different spatial coherent functions and changes decay factors to analyze the effect of spatial correlation on the distribution of the mode contribution factors and the validity of Ritz vectors. The selection criterions of the initial load vectors of computing Ritz vectors and the reasonable computing modes are given.In addition,wind-induced response of east zone steel roof of the Shenzhen Baoli Culture Square theatre is analyzed in time domain method by using wind pressure data measured in the wind tunnel. Based on comparison of the results between time domain method and frequency domain method with different fluctuating wind spectrums and different coherent functions, reasons of differences between the results of two methods are analyzed. It is pointed out that spatial coherence of the fluctuating wind is the main factor which influences the precision of the wind-induced vibration response results. Finally the decomposition method of the non-steady background response and resonant response is given. This method and Ritz-vector method are combined to compute wind-induced vibration response. If accurate fitting formulas of spectrum and coherent function of the fluctuating wind pressure can be obtained, this method possesses great advantage in computing efficiency and accuracy.Finally, the conclusions drawn from this study are summarized, it is found out that some research work should be improved ,and areas in need of further researched are highlighted.