Vulnerability Study Of SRC Column-S Beam Frame Based On Improved Bouc-Wen Model

Steel-reinforced concrete(SRC)column-steel(S)beam frame structure,with advantages of good seismic performance,high bearing capacity and light weight,has been widely used for high-rise and super high-rise buildings in our country.Therefore,the seismic performance evaluation for this kind of structures is particularly important.As the main method of structural seismic performance evaluation,the vulnerability of structure can effectively evaluate the failure probability for the structure,realize the evaluation of structural reliability and estimate the postdisaster damage degree.However,the existing structural vulnerability analysis often uses the assumption of rigid joints for structural failure probability analysis.Although this method simplifies the calculation process,but it fails to consider the influence of the joints of complex hysteretic characteristics on the overall performance for the structure,which reduces the accuracy of the structural vulnerability calculation.In view of this,this paper implements the joint shear hysteretic model,embedding and development in OPENSEES software by improved Bouc-Wen model,and further establishes the finite element model of the frame structure based on the flexible joint assumption,combined with the improved random forest algorithm to achieve vulnerability analysis of SRC column-S beam frame structure in different failure mode,the specific research contents are as follows:(1)First of all,in order to better describe the strength and stiffness degradation characteristics of SRC column-S beam joints in different stages,based on the existing Bouc-Wen model,this paper assumes that the stiffness of the hysteretic spring never changed in the elasticplastic stage,and uses the piecewise linear function to describe the stiffness degradation law of the linear spring in the Bouc-Wen model,and then the existing Bouc-Wen model is modified,a continuous shear hysteretic model suitable for SRC column-S beam joint is established,and the method of model solution and parameter determination based on the experimental hysteretic curve is given.Combined with the relevant literature research and the parameters analysis of the test hysteretic curve,a method to determine the parameters of the joint shear hysteretic model based on the design parameters is proposed.Through the comparison with the test results,the correctness of the model in this paper is verified.The results provide reference to research the seismic performance of SRC column-S beam joint.(2)In order to realize the refined modeling for the finite element model of SRC column-S beam frame structure which based on the flexible assumption,according to the above-mentioned joint hysteretic model,the code of BWBN model is modified to realize the embedding and development of SRC column-S beam joint hysteretic model in OPENSEES software,and the specific call method of the joint element model is further given.On this basis,the finite element model for SRC column-S beam frame structure based on the assumption of flexible joint is established,and verified by comparing with the test results with low cycle loading of SRC column-S beam frame structure.Then the numerical simulation of SRC column-S beam frame structure with different beam column linear stiffness ratio is carried out,and the failure mode of SRC column-S beam frame structure is studied.The research results can provide technical support for the refined numerical analysis of this kind of structure.(3)In order to obtain the optimal failure mode of the structure,based on the research results of the failure mode for SRC column-S beam frame structure and the performance level division method,a method for determining the failure mode of the frame structure is proposed.By adding the failure mode determination process during the growth of the decision tree,the random forest algorithm is improved to establish a vulnerability analysis method.On this basis,combined with the numerical modeling method of frame structure,the incremental dynamic analysis method is used to realize the vulnerability analysis of SRC column-S beam frame structure under different failure modes.Through the comparison of vulnerability curves,the differences of vulnerability curves under different failure modes are discussed.The research results can provide reference to design the SRC column-S beam frame structure.