Experimental Study On Seismic Behavior Of New RC Frame Assembly Joints Based On Bolt Connection

In the frame structure,beam-column joints are responsible for the transfer and distribution of internal forces,to ensure the integrity of the structure,and the role is very important.The joint of fabricated frame structure is easy to become the weak part of the structure under earthquake and destroy first,which leads to the collapse of the whole structure.Therefore,the research of joints is the focus of seismic research of fabricated concrete frame structures.The traditional fabricated concrete frame structure mostly adopts the post-pouring integral joint,which has the advantages of large amount of wet operation and low construction efficiency.Therefore,a new type of RC frame assembly joint based on bolted connection is proposed in this paper.In this paper,the seismic behavior of the new type of joints is studied by means of experiment and numerical simulation,and the theoretical formula of shear capacity of this kind of new type of RC frame fabricated joints is established.The main research results of this paper are as follows:(1)Compared with the assembled integral joints,the bearing capacity and ductility of the new joints are reduced specifically,the bearing capacity is 81% of the assembled integral joints,and the ductility is 83.3% of the assembled integral joints.But the degradation of stiffness and bearing capacity is accelerated.In a certain range of lifting bolt pretightening force,the ultimate bearing capacity of the new joints can reach more than 90% of the assembled integral joints.(2)The failure of the new joints is concentrated at the beam end,which is bending failure,and there is no failure in the core area and column end of the joints,according with the design principle of "strong column and weak beam,strong shear and weak bending",and further showing that it is feasible to propose the bolt connection method in the paper.When the axial compression ratio is less than 0.5,increasing the axial compression ratio can improve the initial stiffness and bearing capacity of the joint,but it will reduce the ductility and energy dissipation capacity of the joint,and accelerate the degradation of the stiffness and bearing capacity of the joint at the same time.(3)The finite element simulation results of ABAQUS are in good agreement with the experimental results,and the error between the experimental value and the simulated value of the ultimate bearing capacity of each joint is less than 9%,which showing that the constitutive model,constraints and boundary conditions used in the finite element analysis can accurately simulate the mechanical properties of the new joints.The results of parameter analysis show that increasing the axial compression ratio and bolt pretightening force in a certain range can improve the ultimate bearing capacity of the new joints.(4)On the basis of test and numerical analysis,the theoretical formula of shear capacity of new RC frame assembled joints based on bolted connections is established.The theoretical calculation result is larger than the test value and the simulation value.Combined with the test failure pattern of the member,it is found that the theoretical value is larger than the test value and the simulation value is larger than the test value and simulation value.It shows that the theoretical formula of shear capacity of new RC frame assembled joints based on bolted connection is reasonable.