Research On Seismic Behavior Of Hollow Steel Reinforced Concrete Column-Steel Beam Joints

Steel reinforced concrete(SRC)structures are widely used in high-rise buildings because of their excellent seismic performance.In order to respond to the call of "housing industrialization",Our research group proposed a new type of prefabricated hollow steel reinforced concrete column-steel beam frame structure with components prefabricated in the factory and then assembled on the spot,so we can realize the assembly of the steel reinforced concrete structure.However,the mechanical properties of the HSRCS joints are not clear due to their novel connection mode and the hollow section form of composite columns.In this context,the seismic performance and shear capacity of the proposed new HSRCS joints are studied by means of numerical simulation and theoretical analysis,including the following aspects:Firstly,the seismic behavior and failure of HSRCS joints under monotonic loading are studied by using abaqus finite element analysis software.The results show that the failure form of HSRCS joints is beam end failure.The internal force between the flange and the horizontal connecting plate is large,so is the the corner of the anti-shear plate that next to the steel beam.and the web of square steel tube,the horizontal and vertical connecting plate are all yielding.The concrete in the joint region cracks under the tensile stress.The stress at the bolt hole of the steel beam is large,but the stress is only extruded and not torn to destroy.On the basis of monotonic loading finite element analysis,the failure mode and force mechanism of the HSRCS joints under the action of reciprocating load are studied.The results show that the location of failure under the action of reciprocating load is the same as that under monotonic loading;Regardless of the connection mode,the deformation occurs at the connection between the flange of the steel beam and the horizontal connecting plate,and the deformation of the flange of the steel beam of the welded joint is small;the maximum stress of the concrete is on the contact surface between the concrete inner surface and the web of square steel,It is because the inner surface of the concrete is in the composite stress state of the shearing force and the internal steel pipe pressure;The tensile and compressive principal stress of the inner and outer concrete is inclined to conform to the mechanical model of the " oblique pressure bar ".Based on the failure characteristics,the steel strength,concrete strength,core square steel tube thickness,axial compression ratio,shear plate thickness,flange thickness of steel beam,the connection mode of joints,the pre-tightening force of bolt are systematically analyzed to know the effects of eight parameters on the seismic performance,ductility and energy dissipation capacity of HSRCS joints.The results show that the load-displacement curves of 17 HSRCS joints are full and fusiform,which shows that the joint has good seismic performance.The displacement ductility coefficient ? of all specimens is 2.53 ~ 5.40,and the best is HSRCS6(integral steel Q345)and the worst is HSRCS2(concrete strength C30).The equivalent viscous damping coefficient of 17 HSRCS is between 0.44 and 0.47.This shows that the beam end has obvious plastic hinge and has good energy dissipation ability.Different parameters have different influence on the energy dissipation capacity and the displacement ductility.In view of the reasonable stress analysis of the core area of HSRCS joints,the mechanism of steel "frame-shear wall" is determined for calculating the shear capacity of HSRCS joints.The rationality of the formula is verified.The results show that the formula is in good agreement with the results of finite element simulation.The proposed formula of shear bearing capacity can be used in engineering design on the basis of further test and verification.