Study On Seismic Behavior Of Steel-concrete Composite Structure Joint Component With Brb For Retrofitting

The reinforced concrete frame structures are widely used in our country.The simple frame structures system has low side stiffness,often damaged seriously under the action of rare earthquake.The researches showed that the reinforced concrete frame structures retrofitted by buckling-restrained brace(BRB)can significantly improve the ability to resist seismic action and wind load,the anti-lateral stiffness and the seismic performance of frame structures.So this technology has been widely used in retrofitting the reinforced concrete frame structures.when retrofitting with BRB,the connection between BRB and the existing structure is usually the method of anchoring the steel plate or planting the steel bar at beam-column joints,then the gusset plate is welded vertically on the post-anchored steel plate to form the connection node.The shortcoming is that the drilling operation is difficult in the stirrup area,the cost of planting and chemical anchorage is high and the construction time is long.This kind of gusset plate may turn with beam-column joint under the horizontal load,which seriously affects the stability and mechanical properties of brace.Therefore,a steel-concrete composite structure brace-connection joint was proposed,which can effectively solve the problems mentioned above.In order to study the seismic performance of the composite component,three 1/2-reduced two-storey single-span RC frames were made for quasi-static test.1 specimen was not retrofitted as the prototype comparison framework.The second specimen was retrofitted with the composite structure and BRB.The third specimen was retrofitted with the steel structure and BRB.The load was imposed under the control of force-displacement mixing.The failure process,the load displacement curve,the skeleton curve and the stiffness degradation curve of 3 specimen,the stress of the steel bar in the core area and the stress state of the plate in the core area were compared and analyzed.The size parameters of the composite component was confirmed by the finite element software ABAQUS.The finite element method was used to compare the stability of steel joint component and steel-concrete composite structure.The results showed that the frame without being retrofitted has low lateral stiffness and bearing capacity,the shear failure occurred on the joint.Two retrofitting frames showed good seismic performance,the stiffness and bearing capacity were greatly improved,the energy dissipation capacity was enhanced,and the damage degree of the joints was smaller than that of the prototype comparison framework.Comparing the steel-concrete composite structure with the steel structure bracing joint,the composite structures can effectively reduce the stress concentration of the steel bar in the core area and the gusset plates,and protect the beam-columnjoint of the frame structures better.Results of the finite element simulation showed that the stress of the concrete was the greatest in the position of the third-row constraint points,and the stress of gusset plates was smaller than that of the steel structure gusset plates.Transfixion cracks appeared at the position of the third-row anchoring points of the composite structures in the test.The results of the finite element simulation were according with the test phenomenon,which showed that the design of the composite structure joint component was reasonable with good seismic performance.