Research On Seismic Behavior Of New-type Joint With Outsourcing And Anchoring For Light Steel Adding Storey

The joint of RC frame-light steel mixed structure is a composite joint composed of concrete and steel structure,which plays an important role in ensuring the overall cooperative work of the mixed structure.Compared with the traditional planting joints which structure is simple and not conducive to the load transfer in complex stress state,a new type of outsourcing and anchoring joint for existing RC frame-light steel adding structure was proposed,and its seismic performance was studied by experimental research and finite element simulation in this paper.The main research contents and results are as follows:(1)On the basis of summarizing and analyzing the stress characteristics of RC frame-light steel storey adding structure,a new outsourcing and anchoring joint for this kind of structure was proposed,meanwhile,a traditional planting joint for comparative research was designed in order to study its seismic performance.The seismic performance include hysteretic characteristics,skeleton curves,strength degradation,rigidity degradation,energy dissipation capacity and beam plastic hinge area rotation of the joints were analyzed contrastively through the quasi-static test of two specimens of joint with 1/2 scale.Results indicate that the joints all invalid by plastic hinge,the new-type joint with outsourcing and anchoring limits the development of cracks in concrete beams effectively,improves the bearing capacity and stiffness,slow the degradation of strength and stiffness,enhances the ability of the plastic hinge of the joint,promotes energy dissipation capacity about 2 times that the hysteretic loop presented asshuttle compared to traditional planted-bar joint.(2)The correctness verification of finite element analysis model.The nonlinear analysis of the new outsourcing and anchoring joints subjected to cyclic loads was carried out by ABAQUS finite element software The internal force distribution characteristics,force transmission paths and failure characteristics of each loading stage were studied in depth.and compared with the experimental results.Results indicate that the failure phenomenon was consistent with the test basically,the load-displacement curve agrees well,the characteristic loads value error was within 15%,and the stiffness degradation ratio was similar,which all indicated the correctness of the finite element model and can be used for subsequent research.(3)Research on the influence of relevant parameters on the seismic performance of new joints.Extended analysis by changing parameters such as axial compression ratio of steel column,beam-to-column stiffness ratio,and steel corrosion rate,results indicate that the increase of the axial pressure ratio makes the second-order effect of steel column more significant,improves the ultimate bearing capacity of the joint and the secant stiffness after yielding,and the seismic performance of the joint can be fully utilized when the axial pressure ratio is 0.3;the stiffness ratio of the beam-column line have a great influence on the initial stiffness,bearing capacity and energy dissipation capacity of the joint,but which accelerates the damage of beam plastic hinge area when the stiffness ratio of the beam-column line is too large,so the beam stiffness should not be too large;the corrosion rate of steel bars affects the ductility of joint primarily,which reduces the bearing capacity of the elastoplastic stage,and results the bearing capacity of the node failure section decreased more obviously.Compared the new outsourcing and anchoring joint with the traditional planting joint through experimental research and finite element simulation analysis,it can be seen that the new joints improves the bearing capacity and stiffness,slows down the degradation of strength and stiffness,increase the constraints on the upper structure,makes the deformation more coordinated for upper and lower structure and continuity of internal force transmission better,limits the development of cracks in concrete beams effectively,enhances the ability of the plastic hinge,promotes the energy dissipation.The scientific basis and technical support for the promotion and application of light steel adding were provided by the research of this project.