Experimental Research On Steel Beam-Circular Tubed Steel Reinforced Concrete (SRC) Joints With Outer Reinforcement Ring Subject To Seismic Performance

Steel tube confined SRC structure not only has the advantage of concrete-filled steel tube structure,but also has the advantage of steel reinforced concrete structure.Moreover,the load bearing capacity of core zone concrete can be greatly improved by the continuous restraint of outsourcing steel tube.Nowadays,the research on steel beam to circular tubed steel reinforced concrete(SRC)column joint is relatively poor,so the in-depth study of this kind of joint is very essential.(1)In this paper,2 steel beam to circular tubed SRC column joints with outer reinforcement ring were designed in two different forms of the connection of outer reinforcement ring and the steel beam flange.The SJ-1 specimen extended the length of outer reinforcement ring,while the SJ-2 specimen set stiffening plates in the connection place of outer reinforcement ring and the steel beam flange.(2)The seismic performance of 2 steel beam to circular tubed SRC column joints with outer reinforcement ring was studied under low cycle reciprocating load.The test results show that: The hysteretic curves of the specimens are full and the equivalent viscous damping coefficients are greater than 0.3,which indicates that the energy dissipation capacity,that is,the seismic performance of the specimen is better than which of the RC joint and SRC joint.The ductility and energy dissipation capacity of the joint can be improved by setting reinforcement plate.Furthermore,setting reinforcement plate can reduce the stress concentration of the connection of outer reinforcement ring and steel beam flange,make the plastic hinge move outside,and then effectively protect the core area of the joint.(3)In order to deeply study this kind of joint in the future,this paper presents a restoring force model.The stress characteristics of the restoring force model are as follows : the positive and negative stiffness under loading and unloading is gradually decreased after the yield of the joint.And the stiffness degradation speed increases with the increase of loading and unloading displacement and the number of cycles.The Bauschinge effect is obvious when the specimen is reloaded negatively.Besides,the stiffness degradation under negative loading is slower than which under the positive loading(4)The numerical simulation software ABAQUS is used to study the seismic performance of the joint.The results show that: numerical simulation results are in good agreement with the test,which verifies the correctness of the numerical simulation.After the analysis of Mises stress of the joint,it can be found that the load could be effectively transferred from the column to the end of beam.The opening place of the outer steel tube is the place with maximum stress of the core area.but the specimen is not yielded basically.Therefore the design of the joint meets the design requirement of "strong column and weak beam" and "strong joint,weak component".