Parameter Analysis Of SMA Spring-Friction Bearing In Isolation Control Of Lattice Shell Structure

With thirty years of China’s economy booming,the large scale engineering structures have been developed remarkably.At the same time,large span buildings continue to emerge,and most of these buildings have large volume and complexity of spatial mechanical behavior.When an earthquake occurs,the seismic performance of these buildings becomes extremely important.Currently people turning light to the theory of isolation control to improve seismic performance of space structures,and the new seismic isolation technology for such structures has been began to developed at home and abroad.The shape memory alloy because of its super elastic properties,durability,corrosion resistance and other excellent features,is gradually obtained research and application in the field of engineering.At present,large size SMA research on seismic isolation devices is still immature.In this paper a new type of isolation device consisting of a flat sliding bearing and several superelastic helical springs entitled as SMA spring-friction bearing(SFB)is proposed.In this study,mechanical experiments and theoretical analysis have been conducted on the proposed SFB device.The main contents and achievements are as follows.(1)Taking the advantage of super elastic properties of shape memory alloy,a unidirectional superelastic SMA spring-friction bearing combining a flat sliding bearing with SMA helical springs is developed.According to the principle of the SFB,the theoretical model of the SFB isolator is established,and the configuration design and parameter analysis is conducted.(2)The unidirectional SMA spring-friction bearing is manufactured,and the experiment is carried out to investigate the bearing’s mechanical properties under complex process of dynamic loading,including simple harmonic and earthquake excitations.According to the test results,the restoring force-displacement curves,isolation and energy dissipation properties of the bearing are analyzed.Studies have shown that the SMA helical springs exhibit stable hysteretic behavior,excellent re-centering performance and large deformation capacity.Under the displacement amplitude,SFB can display stable respond under different seismic waves and provide excellent energy dissipation ability.(3)Based on the theoretical model of the SFB,hysteretic behaviors of SFB is numerically simulated by using the finite element(FE)software ABAQUS.The results shown that the simulation results of hysteresis curves can reproduce the characteristics of test results.Through the comparison and analysis of the equivalent stiffness,cycle energy consumption and equivalent damping ratio,a good agreement is obtained.The main reasons of the differences are also analyzed.(4)The SMA helical springs are applied to seismic isolation and passive control of space structures.A multidimensional SMA spring-friction bearing(MSFB)is proposed.A passively controlled system of spherical lattice shell structure with MSFB is established.Computational models of two lattice shell structure are established with ABAQUS software.Seismic nonlinear history analysis and parameter analysis have been carried out,and the results indicate that the friction coefficient of SFB device has a significant impact on isolation effect.When the friction coefficient select at an appropriate value,the proposed bearing possess good performance.To ensure the isolation effect of lattice shell structure,use of more SMA coil springs can effectively control the peak displacement and residual displacement of MSFB.