Experimental Study On Seismic Performance Of Joints With Perforating Core Zone Of Circular Tubed Steel Reinforced Concrete(SRC) Column-RC Beam

The outer steel tube of tubed SRC column is discontinuous in the joint zone,because it is interrupted in the beam to column connection.The steel tube will not bear the longitudinal load directly,but will confine the core concrete continuously.It inherits the advantages of the concrete-filled steel tubular column and the steel reinforced concrete column.The steel tube exerts a continuous restraining effect on the concrete,which improves the compressive strength of the concrete and the ductility of the concrete.The existence of the shaped steel improves the shear resistance of the column.The presence of concrete compensates for the buckling and collapse of shaped steel and hollow steel tubes.At present,the research on the tubed steel reinforced-concrete column mainly focuses on the static aspects of the components.The research on circular tubed SRC column to RC beam joint has not been systematically developed.The new connections of joints with perforating core zone of circular tubed SRC column-RC beam are proposed.It not only has excellent seismic performance,but also does not expand the joint area and the structure is relatively simple.The following work was done in this paper:1)The experiment designed and manufactured two Joints with Perforating Core Zone of Circular Tubed SRC Column-RC Beam.The methods of three-dimensional cruciform specimen were used to the full-scale experiments.The main change parameters included axial compression ratio of column,perforating area of the core steel tube and the arrangement of stiffening rings and stiffening plates.The influence of various parameter on the seismic performance of the joints was studied in detail.2)The assessment of the test results can be obtained from the low-cycle loading test: the hysteretic curves of load-displacement,the hysteretic curves of moment-angle,the skeleton curves,bearing capacity and displacement of each key points,load-strain curve of each part,etc.Then the plastic deformation behavior,dissipative ability,ductility,strength degradation,stiffness degradation,ultimate bearing capacity and failure modes were analyzed in detail.The ductility coefficients of both joints were all above 3.8,which satisfied the requirements of code for seismic design with ductility.The equivalent damping coefficient and energy dissipation coefficient were much better than ordinary joints of concrete-filled steel tubular column-RC beam.3)Based on the hysteretic model of three broken line of the test results,the hysteretic model suitable for the joints with perforating core zone of circular tubed SRC column-RC beam was established.The stiffness degradation was subjected to regression analysis and it was found that the positive unloading stiffness and positive loading stiffness showed a good logarithmic function,and the reverse loading stiffness and reverse unloading stiffness showed a good exponential function.4)Using finite element software ABAQUS to simulate the test about the joints with perforating core zone of circular tubed SRC column-RC beam,the analysis results were compared with the test results through the stress process,the hysteretic curves and the skeleton curves.The numerical simulation agrees well with the test.On this basis,detailed analysis of the internal force process of the joints revealed its destruction mechanism.