Extreme Value Of Wind Load And Its Uncertainty In The Largespan Roof Cladding And Components

The large-span roof structure has a large span,light weight and high flexibility.Generally,the structure surface flow and the structure aerodynamic interaction mechanism are complex,and it is easy to be destroyed by strong wind.Wind damage to the cladding and components is more common than the main structure.Appropriate and reasonable cladding and components design wind load is the premise to ensure the wind resistance of the cladding and components,and its size depends on the extreme wind load of the structure surface with a certain guarantee rate.The wind tunnel test method is a common method for obtaining the extreme wind load of the cladding and components.Theoretically,the true value of the extremum can be obtained by infinitely repeating the wind tunnel sampling infinitely multiple times.In the wind tunnel test of the wind load of the cladding and components,the sampling times are usually limited and the sampling time is limited.Therefore,the wind load design of the cladding and components is obtained by the probability and statistical method based on the extreme probability statistical model.A reasonable extreme probability model is a prerequisite for predicting the extreme wind load of the cladding and components.In this paper,the large-span flat roof is taken as the research object.From the distribution law of wind pressure on the roof surface,the probability statistical model of wind pressure extreme value and the uncertainty,we provide an estimate of the wind pressure extreme value of the large-span roof cladding and components and the calibration of different extreme value estimation methods.Evaluation criteria based on reliability.This article mainly carried out the following work:(1)Study on wind pressure characteristics of large-span flat roof surface.In this paper,a rigid model wind tunnel pressure test with a scale ratio of 1:200 is applied to the large-span flat roof structure.According to the results of single sampling,the average wind pressure coefficient,the pulsating wind pressure coefficient and the extreme wind pressure on the surface of the structure are obtained.The distribution law of block wind pressure coefficient were systematically studied,and some basic distribution rules of wind pressure distribution on the surface of large-span flat roof structure were obtained.(2)Probability and statistical model of wind pressure on the surface of large-span flat roof and its uncertainty.Based on the results of multiple independent repeating scale rigid model wind tunnel pressure test results of large-span flat roof structure,based on the influence of coefficient of variation on reliability,the shape coefficient,extreme wind pressure coefficient and block shape coefficient are determined.The standard of wind tunnel test sampling times of extreme wind pressure coefficient;based on the classical extreme value distribution,the probability distribution of the measured point and the block extreme wind pressure coefficient is fitted,and the corresponding best fitting distribution is determined;The distribution of extreme values and the influence of different parameter estimation methods and the selection of extreme quantiles on the estimation of wind pressure coefficient extreme values are analyzed.(3)Comparison and calibration of wind pressure extreme value estimation methods for large-span flat roofs.In this paper,several commonly used extremum estimation methods are used: peak factor method,gust coefficient method,short-term segmentation extremum estimation method,multi-block classical extremum estimation method,wind pressure extremum based on second-order moment reliability theory.The estimation method is used to estimate the wind pressure extreme value of the large-span flat roof.The difference of the extreme value estimation results of several methods is compared.The results of the wind pressure extreme value estimation method based on the second-order moment reliability theory are used as benchmarks.A common method is proposed,and the corresponding correction factor is proposed to recommend engineering applications.