Analysis On Seismic Behavior Of Staggered Joints Between Concrete-filled Steel Tubular Columns And Reinforced Concrete Beams

With the diversification development of modern architecture,concrete-filled steel tubular structures are increasingly applied to buildings and have made many impressive achievements.But at the same time,the research on the connection between concrete-filled steel tubular column and beam,especially and reinforced concrete beam,is inadequate;for the force and deformation of the joints will seriously affects the seismic performance of the structure,it is very necessary to do more study on the joints between concrete-filled steel tubular column and reinforced concrete beam.In this paper,according to the east tower project of Zhenjiang Suning Square,a new type of concrete-filled steel tubular column to reinforced concrete beam connection is proposed,the finite element analysis software ABAQUS is applied to conduct nonlinear analysis on the joints under cyclic loading.Numerical analysis results are compared with the experimental results to verify the effectiveness of models.After that,this paper further investigates the effects of length of steel corbel,reinforcement ratio,steel ratio of concrete-filled steel tubular column,axial compression ratio and type of vertical stiffening plate on the seismic performance of normal concrete-filled steel tubular column to reinforced concrete beam joints through parametric analysis.This paper also investigates the effects of staggered height on the seismic performance of staggered joints.After that,this paper conducts analysis on the mechanics characteristic of concrete-filled steel tubular column to reinforced concrete beam staggered joints,and the shear transferring mechanisms of various type of staggered joints and calculation methods of shear in joint core area are proposed.The results show that: The finite element models established in this paper could well simulate the performance of rectangular concrete-filled steel tubular column to reinforced concrete beam joints under actual loading and have a good applicability and accuracy.The increasing of length of steel corbel can enhance the anchorage effect of beam reinforcement,as well as the strength and stiffness of the joint,for the joints designed in this paper,the joint with 60 d long steel corbel has the best energy dissipation capacity.Higher reinforcement ratio and steel ratio of column can enhance the strength and stiffness of the joint,while the energy dissipation will be relatively declined.Lower axial compression ratio is recommended to get a higher strength and energy dissipation compacity,as well as to prevent the bending failure of column.The application of vertical stiffness plate in the column can significantly enhance the strength,stiffness and energy dissipation capacity of the joint.The mechanical behavior of concrete-filled steel tubular column to reinforced concrete beam staggered joints is significantly affected by the staggered height and the loading direction.With the increasing of staggered height,the strength of the joints increase at first and then drop and keep stable eventually,the joint achieves the highest strength when the staggered height is 0.64 times of the height of beam.The force transferring mechanism of the concrete in the staggered joint can be simplified as a diagonal struts model.For the first class of staggered joints,the joint will form a diagonal strut to transfer shear force;and for the second and third class of staggered joints,the joint will form three diagonal struts to transfer shear force.For the first class of staggered joint,the weakest section of bearing shear is in the middle of the joint core area;for the second and third class of staggered joint,the weakest section of bearing shear is in the top or bottom of the joint core area.Summing up the research results,this paper systematically studies the seismic behavior of square concrete-filled steel tubular column to reinforced concrete beam normal connection and staggered connection,and on the basis of the research,design suggestions,calculation method of shear in joint core area and problems to be solved were given.