Importance Analysis Of Random Variables And Vulnerability Analysis Of SRC Frame Structures Under Earthquake

The seismic intensity has a great influence on the analysis of structural seismic demand and seismic vulnerability.Similarly,the uncertainties of structures also have a certain influence on them.In addition,when analyzing the vulnerability of frame structures,a single damage index of the whole frame structure is often used,such as the maximum value of the maximum inter-story displacement angle of each floor to describe the vulnerability of frame structures,while the correlation between seismic demands of each floor has been ignored.Therefore,it is necessary to study these uncertainties based on the effective methods,and the correlation between seismic demands of each floor should be considered in the vulnerability analysis of frame structures.However,it is difficult to consider the correlation between seismic demands of each floor.In this paper,the importance of random variables in steel reinforced concrete frame structures is firstly analyzed,the influence of random variables on seismic demand and seismic vulnerability of structures is studied,and a seismic vulnerability analysis method for frame structures considering floor correlation is given.The main work includes:(1)A new sampling method is given to study the impact of random variables on output,and the new variance importance measure index is obtained,which is more accurately in the case of a small number of samples.On this basis,the non-linear time history analysis of steel reinforced concrete frame structure is carried out,four kinds of structural seismic demand are obtained,and the importance analysis is carried out.The variance importance index of each random variable to seismic demand and seismic vulnerability is obtained.The seismic vulnerability and seismic demand of random variable to structure are analyzed respectively.Comparing the analysis results of common methods,the results show that this method is accurate and effective,and can greatly reduce the number of samples of the importance analysis of large and complex structures.(2)Several machine learning algorithms are used to obtain the importance index of random variables.Then,the importance index of SRC frame structure is analyzed,and the importance indexes of each random variable to the seismic demand of structure and the seismic vulnerability of structure are obtained,which makes the number of needed samples further reduced.The importance analysis method based on neural network quantile regression clearly describes the statistical characteristics of output response in its distribution range in detail,and the influence of random variables on seismic demand and seismic vulnerability under various quantile conditions are obtained.(3)The method of information entropy importance measure analysis is applied to the importance analysis of input random variables to structural seismic demand and seismic vulnerability.Firstly,the theory of information entropy is elaborated.Then the importance measure index of information entropy is given.The importance analysis method based on the information entropy coupling Hermite orthogonal polynomial estimation is used.At the same time,the new efficient sampling method is used to obtain the information entropy importance index of random variables for seismic demand and seismic vulnerability,and the commonly used kernel density estimation method is compared to verify the validity of the solution method.(4)Copula function is firstly used to describe the correlation between the seismic demand of each floor in SRC frame structure,and the correlation between the marginal distribution function of seismic demand of each floor and the seismic demand of each floor is separated.Then the seismic vulnerability analysis method of frame structure based on Copula function is given.When estimating the relevant parameters in Copula function,two nonparametric methods,which are,respectively,the orthogonal polynomial estimation and the kernel density estimation are used.The re-sampling method and the first-order boundary method are adopted to compare and verify the validity of the calculation results.The influence of the correlation between the seismic demands of each floor on the seismic vulnerability of frame structures is also discussed.