Influence Of Opening On The Fluctuating Wind Characteristics Of Stadium Cantilever Roof

The structures of long-span present characteristics of light weight,low damping and large flexibility.The airflow on the roof surface is relatively blunt and sensitive to the wind,making these structures easy to be damaged partly or as a whole under the action of strong winds.At the same time,large-span structures need to meet the requirements of function and artistic modeling,which leads to the different shapes of large-span structures.Therefore,the current load code for the design of building structures cannot fully meet the design needs of various large-span structures.For different large-span structures,the reference resources for wind load design are also quite limited.As a result,it is necessary to carry out the research on the wind effect of the long-span stadium systematically.This paper focuses on the fluctuating wind effect of long-span stadium.a series of wind tunnel tests of rigid model pressure measurement are carried out for the open-hole model and the no opening model.Time series coefficient of wind pressure on the roof surface before and after the opening was processed,the fluctuating wind pressure value distribution on the roof surface before and after the opening was studied,and the influence of the opening on the fluctuating wind pressure value of the roof under different wind directions was compared and analyzed;The traditional non-Gaussian region and the Gaussian region division method are discussed in this paper.The non-Gaussian region division standard of the large-span stadium roof is proposed by using the non-parametric test method,and the influence of the opening on the Gaussian of some measuring points is analyzed.The classification and solution process of the stationary time series analysis model are briefly described,and the auto regressive model is selected as the statistical model for the power spectrum characteristics estimation of the fluctuating wind pressure.The estimated order p=40of the power spectrum function is discussed by FPE criterion and AIC criterion.The improved covariance method was used to estimate the power spectrum model by Matlab programming.The effect of roof openings on fluctuating wind effect and its causes were discussed in detail.The main conclusions are as follows:(1)The fluctuating wind pressure distribution on the roof surface before and after the opening changes with the change of wind direction angle.Direction at 60°angle of the fluctuating wind pressure value maximum of 0.45.The distribution of the fluctuating wind pressure value is affected by the shape characteristics of the incoming flow building structure.The hole opening reduces the fluctuating wind value of the point at the edge of the hole with high fluctuating pressure value before the hole opening,and has little effect on the point with low fluctuating pressure value before the hole opening and after the hole opening.The rate of reduction is between30%and 55%for the fluctuating wind value of the hole edge measuring point with higher fluctuating wind pressure value before partial opening.(2)Multi-order moment method is adopted to obtain skewness and kurtosis values of each measuring point on the roof surface through the third-order moment and the fourth-order moment of the wind pressure time series.The?~2 goodness-of-fit test method and the skewness and kurtosis test method are proposed,and the significance level corresponding to the guarantee rate of 99.38%is 0.025.The non-Gaussian region division standard is given as S(29)0.4 or K(29)3.5.The change of the Gaussian property after the hole opening is consistent with the change trend of the fluctuating wind pressure.Under the condition of no opening,the value of the peak factor should be greater than the load specification g=2.5.For the open-hole condition,the value of the peak factor can still be g=2.5.(3)For some areas that are greatly reduced by characteristic turbulence after opening,the modeling of wind pressure spectrum before opening should be dominated by characteristic turbulence,while the modeling of wind pressure spectrum after opening should be dominated by atmospheric turbulence.In the non-Gaussian region,characteristic turbulence is formed due to the separation of air flow before the opening,which leads to the violent reattachment collision of air flow at the measuring point at the back edge of the roof and many smaller scale eddies.In the high frequency part of the power spectrum,the spectral curves of the leading edge and the trailing edge produce splitting phenomenon due to the influence of characteristic turbulence.The opening reduce the influence of characteristic turbulence on the front and rear edges of the roof.Since there is almost no characteristic turbulence in the Gaussian region,the wind load on the roof surface before and after the opening in these regions is affected by the incoming turbulence,and the opening has no effect on the change of characteristic turbulence.