Research On Hysteretic Behavior Of An Innovative Self-Centering Steel Brace

Prestressed wires and Shape Memory Alloys(SMA)are commonly used in existing selfcentering steel brace.When prestressed wires are used as the recovering components,the wires must be in the elastic state.However,the limited length of the brace leads to the limited axial deformation capacity.The huger axial deformation capacity can be achieved by using SMA as the re-centering component.In fact,the energy dissipation component has such full hysteretic characteristic that requires a large amount of SMA to reduce residual deformation.In this paper,a new type of Self-Centering Steel Brace(SC-SB)which use steel strips with pinching hysteresis characteristics and SMA is proposed.The brace uses two sets of steel strips to attain the characteristics of pinching hysteresis.Also,the steel strips provide axial bearing capacity,stiffness and energy.The new SC-SB achieves the re-centering function by winding SMA wire on the movable slider inside the brace.In this paper,theoretical analysis,experimental researches and numerical simulations are carried out on the hysteretic performance of the SC-SB.The contents are as follows:(1)The detailed structure of the new SC-SB brace is proposed.The axial bearing capacity,stiffness and energy dissipation of the tensile strips with significant pinch phenomenon are achieved.The SMA wire is always in tension and the strips only bears the tension.The working principle of the new SC-SB brace is analyzed in detail,and the moreover calculation formula of the bearing capacity of the new SC-SB brace is given.Based on the two-fold line model of the tensile steel strips and the superposition principle of SMA material,the restoring force model of the new SC-SB brace is constructed.(2)Five new SC-SB brace members only with energy dissipation steel strips were designed and manufactured in 1/3 scales.The hysteresis performance,energy dissipation capacity,maximum horizontal bearing capacity and lateral stiffness of the steel brace are emphatically studied.(3)The microfinite element model of the test specimen was established by ANSYS program and the cyclic loading analysis was carried out.The accuracy of ANSYS program analysis was verified by comparison between simulation results and test results.(4)The parameter finite element analysis of the brace is carried out by using the ANSYS program for the pure re-centering steel brace with SMA wire,the brace only with energy dissipation steel strips and the new SC-SB brace.The influence of the key design parameters such as type of SMA,size of SMA and size of steel plate on the steel brace hysteresis performance was studied.