Seismic Performance Analysis Of Superposed Shear Wall-floor Slab Joint Under Vertical Earthquake

Superposed structure is widely used as prefabricated components,among which cantilever structures used as high-rise building balconies or others must consider the influence of vertical earthquakes.In order to make the mechanical performance and integrity of superposed structures reach or even exceed the effect of cast-in-situ components,the weak points of prefabricated buildings are often studied,especially in the connection joint of prefabricated buildings.At present,no one has studied the influence of the cantilever structure in the form of superposed floor slab on the joints under vertical seismic action.In this paper,a superposed shear wall-superposed floor slab joint specimen is designed and numbered S-1,and the low cycle reciprocating load experiment is carried out at the end of the floor slab to simulate the effect of vertical earthquake on the floor slab,analyzing the seismic property of the superposed shear wall-floor slab joint,simulating and optimizing the results of FEM according to the experiment.The main research work and results are as follows :1)The superposed shear wall-floor slab joint specimen was designed and manufactured,and the low cycle reciprocating load is applied at the end of the floor slab.Analyzing the seismic performance of the superposed shear wall-floor slab joint specimen with experimental parameters.The experimental results show that the cracks concentrated on the floor slab and the concrete of the floor slab are crushed around the joint.There are no cracks on the back of the specimen and the joints are almost not damaged,indicating that the superposed floor slab will not cause damage to the joints under vertical earthquake,which meets the requirements of strong joints and weak components in structural design.2)According to the hysteretic curve of superposed shear wall-floor slab joint specimen,the hysteretic curve presents the phenomenon of asymmetric bearing capacity,and the maximum bearing capacity in the forward stage is smaller than that in the reverse stage.The main reason for the large gap is that the longitudinal reinforcement in the precast slab bends out of the precast slab by bending,and then enters the cast-in-situ layer to be anchored.Therefore,there is no direct connection between the precast slab and the shear wall in the floor slab,so the bearing capacity of the specimen is less than that of the cast-in-situ surface when the precast slab is pulled.In summary,the connection mode between superposed floor slab and the wall should be avoided and the corresponding optimization is proposed in this paper.3)According to the stiffness degradation curve of test specimen obtained from the hysteresis curve,it can be seen that during the loading process of the specimen,the stiffness degradation curve do not show obvious mutation,and the stiffness degradation of the specimen is relatively uniform.In addition,the S-1 specimen still maintains a certain stiffness at the late loading stage.The curve shows that the castin-situ part of the floor slab of the S-1 specimen and the precast slab can be subjected to synergistic force,and has good integrity and deformation ability.According to the energy dissipation coefficient and ductility coefficient,S-1 specimen has certain energy dissipation capacity,can absorb certain seismic energy,and has good inelastic deformation capacity.4)The numerical simulation is carried out by ABAQUS finite element software and numbered SW-1.Comparing the data of the experiment with the damage nephogram,hysteresis curve and skeleton curve of the simulation,determining the result of FEM is reliable,which can provide reference for subsequent experimental research.5)Optimizing the design of the specimen from the plate thickness and the connection mode of the steel bar between the prefabricated plate and the shear wall by ABAQUS,and the simulated low cycle reciprocating load is applied to the four specimens.The four specimens can effectively improve the bearing capacity of the specimen in forward push,solving the problem of low bearing capacity under forward push in the experiment,and improve the seismic bearing capacity of the superposed floor slab in practice.However,the connection form of precast slab longitudinal reinforcement and shear wall is changed has larger hysteresis loop area and better symmetry higher ultimate bearing capacity and energy dissipation capacity,comparing with the specimens with different slab thickness.In summary,considering the superposed floor slab as a building component resisting the vertical earthquake,the precast slab longitudinal reinforcement should be directly extended to connect with the shear wall.Although the simulation and optimization are carried out by ABAQUS,a large number of experiments are still needed to verify whether the optimization is reasonable in the later stage.