Experimental Study And Finite Element Analysis On Seismic Be Havior Of Double Beam Joint With Wide Column

With the rapid development of national economy,the structural forms of existing buildings can no longer meet the demands of nowadays society,so that various local governments have to speed up the progress of transforming old cities.However,the transformation performed by government’s planning department could only change the internal use functions on the premise of protecting the original style of old building.In response to the call of times,a large number of intelligent architects in China have turned their attention to the underpinning structure,and double-branch underpinning structure has emerged as a new concept.Based on researching the seismic performance of wide-column double-beam joints,this thesis mainly obtained the research achievements are as follows:In this thesis,the experimental study of wide-column double-beam joints under low-cycle reciprocating loads was carried out,including the test parameters of axial compression ratio and longitudinal beam.The experiment studied the influence rule of above parameters on the ultimate bearing capacity of the joints,and analyzed the variation law of joints’ ultimate bearing capacity under low-cycle reciprocating loads,along with the seismic performance of joints such as strength degradation,stiffness degradation,ductility and energy dissipation capacity.According to the experimental results,the ultimate bearing capacity of joints in this kind is better than that of ordinary concrete joints.Meanwhile,although a certain pinch emerged in the load-displacement curve of joints in this kind due to the existence of certain bond slippage between steel and concrete,the stiffness and strength degeneration of joints was stable with better energy dissipation capacity,ductility and seismic performance.The finite element analysis model of wide-column double-beam joints under low-cycle reciprocating loads was established in this thesis,which considers the effects of non-linearity of materials and geometry,interactions between components and initial defects.Therefore,a method for valuing the damage indicator of concrete that is applicable to concrete plastic damage model is given and applied to the finite element model.The comparison of test results of joints under reciprocating loads verified better accuracy and reliability of finite element model.Based on the experimental results and finite element model,the working mechanism of wide-column double-beam joints was analyzed in detail.The internal forces,deformation distribution,and development of stress as well as damage of various components of joints during the whole process of stress were clarified.The influence laws of axial compression ratio,longitudinal beam,concrete strength,ratio of beam bending strength of on the ultimate bearing capacity of the wide-column double-beam joints;the crack development of joints under the low-cycle reciprocating loads and ultimate failure modes;influence laws of joints’ seismic performance were analyzed systematically.The research results can provide certain reference for the seismic design and experimental study of wide-column double-beam joints,so as to lay proper foundation for the follow-up research of joints in this type.