| Large-span roofs are usually characterized by light weight,large flexibility,small damping and low natural frequency,wind load is often the main control load in structural design.In recent years,wind damage to the main body and the surrounding structure of the roof is common in worldwide,which indicates that the wind resistance design of the large-span roof is not comprehensive enough.Therefore,it is significant to study the wind load and wind-induced dynamic response of large-span roof structures.In this paper,we discussed the wind pressure distribution characteristics,estimation of extreme wind pressure and the calculation methods of wind-induced vibration responses of large-span roof through wind tunnel test.The main contents are summarized as follows:(1)Based on the Shenzhen International Convention and Exhibition Center,the main process of wind tunnel pressure test for large-span roof structure is introduced.According to the wind tunnel test data,the characteristics of the average wind pressure distribution of monomers and groups working condition of the standard exhibition hall under the typical wind direction angle are studied,and the interference effect of the upstream exhibition hall on the downstream standard exhibition hall is analyzed.The results show that the roof has a large negative pressure and gradient in the upwind cantilever eaves and corner area.At certain wind angles,the wind load of the local area of downstream roof will increase significantly due to the interference of the upstream roof.(2)Based on the wind tunnel test of cylindrical roof,we analyzed the characteristics and laws of wind pressure time history statistics in different lengths samples.The long duration sample estimation results of the peak piecewise average method were used as the standard to measure the estimation accuracy of the short duration sample using the peak piecewise average method,the peak factor method(g=3.5)and the modified Hermite moment model method.Combined with several different types of large-span roof structure practical engineering projects,the peak piecewise average method and the modified Hermite moment model method were further used for the parallel comparison of extreme wind pressure estimation.The results show that when the duration of the wind pressure sample is short,the skewness and kurtosis fluctuate greatly.As the sample time history gets longer,it tends to be stable,while the mean and standard are very stable.According to the results of the extreme wind pressure estimation of the cylinder roof and the actual project,the peak piecewise average method is an ideal and stable estimation method.(3)The basic principles of wind-induced vibration response calculated by the time domainmethod and several frequency domain methods are introduced,take Shenzhen International Convention and Exhibition Center(new design)standard exhibition hall as an example,the wind-induced response of the roof were calculated by direct integration in time domain and harmonic excitation method(HEM)in frequency domain respectively.Meanwhile,traditional natural vibration modes and Ritz modes based on wind load by proper orthogonal decomposition(POD)were utilized in the frequency domain analysis by HEM,then,compare their computational accuracy and efficiency.The results show that the frequency domain method requires 500 traditional natural vibration modes to obtain satisfactory results,when the parametric mode is insufficient,the error distribution of the response results is different in different parts of the roof.As for the calculation efficiency,the direct integration method by SAP2000 takes about 6000 s and HEM only need 193 s even if take 500 parameter modes.And the same accuracy of 500 traditional natural vibration modes can be achieved by using 120 load-dependent Ritz modes,but the time required(32s)is reduced to 1/6,which proved the efficiency of HEM based on Ritz-POD. |
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