Study On Seismic Behavior Of A New Assembly Type Joints With Concrete-filled Square Steel Tube Column And Reinforced Concrete Beam

In recent years,concrete-filled steel tubular structure is widely used in engineering because of its good performance and unique advantages.Many scholars at home and abroad have studied CFST structure,especially the research on single component is relatively systematic and mature;however,the research on joints is relatively less,and has not formed a complete research system.At present,nodes are faced with many problems in the process of design and construction: simple node design is conducive to later construction,but it will affect the bearing capacity and safety of the structure;complex design will lead to later construction troubles and extend the construction period.The appearance of assembly joint can effectively solve these problems in the joint.The construction of assembly joint is convenient,can shorten the construction period,is convenient for transportation,is conducive to the conservation and recycling of resources.On the basis of CFST structure and fabricated joint,this paper puts forward a new type of CFST column reinforced concrete beam fabricated joint,and studies the seismic performance of the joint.The research contents and conclusions in this paper are as follows:(1)The ABAQUS finite element analysis software is used to model side joints connecting the beam and column of reinforced concrete frame.And then,the analysis results are compared with the test results,which verify the validity and correctness of the modeling.(2)The ABAQUS finite element analysis software is used to model the joint connecting composite concrete-filled steel tubular column and H-beam.Also,the analysis results are compared with the test results,The result show the validity and correctness of the modeling.(3)A new joint connecting composite concrete-filled steel tubular column and H-beam is proposed.A traditional cast-in-place concrete edge joint model and a new type of CFST column-reinforced concrete beam edge joint model are established for comparative analysis,and the differences of parameters such as hysteretic curve,skeleton curve and equivalent viscous damping coefficient between the two joint models are studied.The results show that under the same loading system,the hysteretic curve of the new type of CFST column reinforced concrete beam assembled joint is more full,the ductility coefficient is 3.95,and the energy consumption coefficient is 0.25,which shows that the ductility and energyconsumption performance of the new type of joint are better.And the new type of joint realizes movement the plastic hinge.Therefore,the new node has better theoretical research and practical application value.(4)Considering the variable parameters of the length of the post cast section,the axial compression ratio of the column,the strength of the beam concrete,the diameter of the anchor bar and the length of the angle steel,seismic performance of the new joint connected CFST column and reinforced concrete beam are studied,respectively.Then reasonable value range of each parameter are obtained.It is suggested that the length of the post pouring section should not be less than 350 mm,because the short post pouring section will reduce the bearing capacity and ductility of the joint;the anti-seismic performance of the new joint is greatly affected by the axial compression ratio,when the axial compression ratio gradually increases from 0.1 to 0.4,the maximum difference of the bearing capacity is 63.68%,the decline is very obvious,and it is suggested that the axial compression ratio should be controlled within0.1-0.3;the strength grade of the beam concrete C30 and C40 are suitable.It is suggested that the diameter of the anchor bar should not be less than 14 mm.When the length of the angle steel is 180 mm,performance of the new joint are better.(5)In order to further study the seismic performance of the new type of CFST-RC beam assembly joint,the modeling analysis of the plane joint,the space corner column joint and the space side column joint of the new type of joint is carried out,respectively.It is found that although the form of the plane joint and the space joint are different,the failure position of the joint is basically the same,which occurs in the post cast section and the prefabricated beam.The seismic performance of the space side column joint is slightly worse than that of the plane joint and the space corner column joint.