Research On Experimental Substructure Of Steel Frame For Seismic Hybrid Test

Among the current seismic test methods,as an effective seismic research method,the hybrid test method of substructures has made considerable progress.The substructure seismic hybrid test method combines numerical analysis and physical loading,which means that large-scale structures are tested by intercepting test substructures.This method can reduce the demand on the test site.However,the simulation of complex boundary conditions in the substructure hybrid test method is a difficult point,and it is also the key to ensure the feasibility and accuracy of the hybrid test.The boundary condition simulation method based on the inflection point can well perform the simplified loading of the experimental substructure in the elastic phase.However,while discussing the applicability of this method when the structure enters the strong nonlinear phase,few researchers have obtained good research results.This paper conducts theoretical and experimental research on this problem,and discusses the feasibility of using the boundary condition loading method based on the inflection point to carry out the structural seismic collapse test.The main contents are as follows:(1)In this paper,the steel frame is designed according to the "Code for Seismic Design of Buildings",and the frame is scaled using the incomplete scaling method.Select one of the three-story,two-span steel frame to establish an Open Sees finite element model to simulate the horizontal seismic force.The whole process from elasticity to strong nonlinearity,the influence of beam-column stiffness ratio,ground motion,span number,axial compression ratio,etc.,on the change of the position of the inflection point is studied.(2)By analyzing the shear deformation,bending deformation and the second-order effect of axial force in the frame column,the mechanical mechanism of the change of the position of the inflection bending point and the change of the internal force distribution of the steel frame structure under the action of a horizontal earthquake is explained.Among them,bending deformation is the main reason that the position of the inflection point deviates from the column in the elastic phase,and the second-order effect is the main reason for the increase of the difference in shear distribution after entering the plastic phase,and makes the structure more susceptible to damage,and should not be ignored.(3)Different inflection point positions are selected and the inflection point method is used to simulate loading of the test substructure.The loading error of the elastic phase and the strong nonlinear phase are compared.Discussed the influence of the change of the position of the inflection point on the simulation of the boundary conditions of the test substructure under the change of the beam-to-column stiffness ratio.The loading boundary selection method of the whole process of loading the boundary conditions of the test substructure is proposed.(4)A two-story,two-span steel frame model was designed for seismic Pushover test research.The test can clearly reflect the staged seismic performance of the structure.According to the results of the finite element analysis,the detailed measuring point layout and loading device layout are carried out,and the multi-point coordinated displacement control loading is carried out.The comparison between the test results and the finite element analysis shows that the theoretical analysis in this paper is correct and effective.