Study On Seismic Behavior Of Prefabricated Prestressed Assembled Monolithic Concrete Frame Structure(Scope System)

Prefabricated prestressed assembled monolithic concrete frame structure(scope system)is a kind of post-pouring monolithic frame structure with lap joint connection and prefabricated prestressed stacking members.The structure has the advantages of convenient construction of joints,good quality of components,energy saving and environmental protection.However,whether the lap joint connection can meet the requirements of plastic development of joints,and whether the framework of structural system can ensure the seismic performance satisfy "equivalent pouring" is not clear.In view of the problems above,this paper has done the following works:(1)Taking the cast-in-site frame joints as prototype,the middle joints in the framework of scope system are designed based on the principle of "three strength and three weakness".The section size and reinforcement settings are the same with the cast-in-site joints.The beam end plastic hinge of the node is connected by lap.The interface between the old and new concrete interface of the joint interface,the horizontal overlap surface and the vertical joint surface of the key groove area are respectively "artificial cutting hair" and setting shear key.Finally,two joints of full-scale scope structural system and a corresponding joint of cast-in-situ structural are constructed.Among them,Different concrete strength of two joints of scope structural are used as the parameter variables.(2)Low-frequency cyclic loading tests were carried out on the three joints;the crack development,yield and ultimate damage of the joints were observed.The experimental results show that,failure of the scope joints is the same as that of the cast-in-site joints,and the hysteresis curves are full.The bearing capacity and the stiffness are degraded;the ductility and the energy dissipation are close;and the structure strength of the joints are reliable while the connecting steels are not sliding.There is no relative slip between the old and new concrete interface,indicating that the seismic performance of the scope joints can meet the requirement of "equivalent pouring".(3)The finite element software ABAQUS is used to analyze the testing joints nonlinearly.The failure model and hysteresis curve of numerical analysis are close to the experimental results.Based on the above modeling method,a two-tier plane frame structure and the corresponding cast-in-site frame model are established,and finite element analyses under monotonic loading and low-frequency cyclic loading are carried out.The simulation results show that stiffness,force,development of plastic hinge and hysteretic performance of the two frames are very close.Parameter analysis of the scope structure system,results show that the axial compression ratio,the number of prestressing tendons and the reinforcement ratio of U-shaped tendons have great influence on the hysteretic performance of the scope structure system,and the load and the stress of prestressed tendons is less.