Study On The Performance Of The Shape Memory Alloy As The Shear Connector Of The Steel Frame Concrete Wall Structure

Shear connectors play a vital role in the steel frame concrete wall structure,and the setting of the shear connectors can ensure the reliable transmission between the horizontal load and the shear wall,while the combination of the two is a whole,avoiding the premature formation of the shear wall which causes the infill wall to be crushed.In the steel frame concrete wall structure,the shear connectors are complex and often in a state of tension and shear coupling.Under the action of horizontal force,the shear resistance of shear connectors is greatly affected.At the same time,under the action of earthquake or dynamic load,the shear connectors are prone to the low cycle fatigue damage.As a set of sensing and driving function in one of the smart material,SMA has many advantages such as shape memory effect,super elasticity,damping property and resistance characteristic,which has been widely used in the design of structure,vibration control,reinforcement and repair and structure detection.SMA materials in the process of loading and unloading cycles show good fatigue resistance,which can provide a possibility for the application of the shear connectors in the steel frame concrete wall structure.In this experiment,the shape memory alloy material is processed into a standard bolt shear connector used in the steel frame concrete wall structure.The mechanical properties of shape memory alloy shear connectors are studied by considering the factors such as loading mode,horizontal force,section size,concrete strength and so on.Firstly,mechanics performance Study of SMA.Heat treatment to SMA material,to change the temperature of phase change of the SMA material,make it has good material properties.Then the heat treated SMA materials by differential scanning calorimeter test,so as to determine the temperature of phase change of materials.On this basis,the tensile test of SMA bolt,understand the mechanics properties of SMA bolt shear connector.Secondly,study on the drawing of the SMA bolt considering the influence of the bond force.By test,get test specimens load-slip curves,and the ultimate load was 8.6kN,and the limit displacement was 1.15mm.Bond strength between the SMA bolts and concrete is mainly made by chemical glue focus,friction and thread and Mechanical bite force between thread and concrete.In different stages of force,the role of the various components is not the same.Once again,comparison of the performance of the SMA bolt and the ordinary bolt shear connectors under the repeated load.At the initial stage of loading,the displacement of SMA shear connectors is smaller than that of the ordinary bolt shear connectors,and the displacement of the load is zero,the residual deformation is small,and the elastic stiffness is bigger than the ordinary bolt shear connector.The ductility factor of SMA bolt connection and the plastic deformation ability are bigger,the strength or the bearing capacity of the bolt is slow,and the seismic energy can be absorbed and dissipated more than the common bolts.Simultaneously,SMA stud shear connectors of hysteresis loop of plumpness to far greater than ordinary shear connectors,that the energy dissipation ability is stronger than the common shear connectors.Finally,considering the influence of horizontal force,bolt size,concrete strength and reinforcement cage layout on SMA shear connectors.Through the experiment,we can get the following conclusions:the level of the test piece is affected by the level force,the greater the level force,the smaller the bearing capacity of the specimen,the smaller the displacement quantity,the more brittle failure.Increasing the size of the SMA bolt shear connector can effectively improve the ultimate bearing capacity and ultimate displacement of the test pieces,while improving the effect is more significant.The higher the concrete strength grade,the greater the ultimate bearing capacity of the SMA connector,the smaller the ultimate displacement.