Study On The Mechanical Properties Of Vertical Shear Wall Joint Based On Concrete-filled Steel Tube Keys

For assembled shear wall,vertical connection is an important connection part to ensure its bearing capacity,ductility and energy dissipation capacity.Different vertical connection technologies of assembled shear wall also have different effects on the seismic performance of shear wall.Therefore,by comparing the existing vertical connection technology,the research group proposes a simple installation,convenient construction,and can provide better bearing capacity and deformation capacity than cast-in-place.In this paper,two vertical connection modes of shear walls are designed,namely steel gusset type vertical connection and concrete-filled steel tube key vertical connection.Steel gusset type vertical connection is the use of l-shaped steel plate welded on the steel plate with holes,the steel gusset plate will be up and down two shear walls of the l-shaped steel plate buckle,and in the buckle area cast concrete fill,forming steel gusset type vertical connection.The l-shaped steel plate bears part of the pressure and all the tension from the shear wall.The vertical connection of concrete-filled steel tube bond is welded on the perforated steel plate with a rectangular steel groove of a certain depth,and the rectangular steel groove of the upper and lower shear walls is buttoned.The space inside can be arranged with precast concrete blocks to improve the bearing capacity of the concrete-filled steel tube bond.The rectangular steel groove can be welded as a whole.The rectangular steel groove bears part of the pressure and all the tension.Based on the finite element software ABAQUS,the finite element model of cast-in-place shear wall under horizontal reciprocating load is established.Based on the finite element analysis of steel gusset type vertical connection,concrete-filled steel tube key vertical connection and the same cast-in-place shear wall,the mechanical properties of the three are compared.Considering that the bearing capacity and ductility should not be lower than that of the same cast-in-place shear wall,the final choice is the concrete-filled steel tube key vertical connection.For the shear wall connected vertically by the steel tube concrete key,a total of 11 shear wall models based on the vertical connection of the steel tube concrete key are designed by changing the five main factors of the concrete strength,the thickness of the steel plate with holes,the thickness of the steel groove,the height of the steel groove web and the steel strength.The stress process of the shear wall model under constant axial pressure and lowcyclic load under different factors is simulated.According to the simulation results,the hysteretic curves of the model under different factors are full,showing a "bow" and good energy dissipation capacity.The skeleton curves were extracted respectively to calculate the displacement and load of the nodes at the feature points.On this basis,the displacement ductility coefficient,energy dissipation coefficient and equivalent viscous coefficient were calculated by the formula,and the stiffness degradation curves under different influence factors were compared and analyzed.According to the existing codes and literatures,the theoretical calculation of shear capacity of concrete-filled steel tube joints connecting shear walls vertically under different factors is far greater than the simulated value of ABAQUS,which indicates that this vertical connection mode has better connection performance and improves the shear capacity of shear walls without shear failure.When calculating the bearing capacity of the normal section of the shear wall under eccentric compression under different factors,it is found that the bearing capacity of the shear wall is all less than the simulated value,indicating that the bearing capacity of the shear wall is insufficient and the bending failure of the normal section occurs at the joints.A simplified formula for calculating the flexural capacity of the shear wall is obtained by means of the regression of the calculated data.This paper redesigns the shear wall connected vertically by the concrete-filled steel tube(CFST)key,verifies the accuracy of the regression formula,and provides reference for the follow-up research of the shear wall based on this connection mode.