Study On Perfornance Of SMA Spring-friction Bearing For Isolation Control Of Space Grid Structures

With the improvement of comprehensive national strength and economic level, the number of large space or large span structures in our country is growing up. Space structures are flexible and have low damping ratio. As a result, the structural system will produce signicicant disturbance and vibration under dynamic load including seismic load and wind load. However, traditional seismic resistance technology is usually difficult to solve such problems. At present, vibration control technology is becoming an effective method for seismic prevention of engineering structures.In structural vibration control, the most widely used isolator are the laminated rubber isolation, the pure friction isolation device, friction pendulum bearing. Due to the low energy dissipation capability of laminated rubber bearing, the produced large horizontal shear deformation easily lead to bearing failure.The pure friction isolation devices have flat sliding surface without re-centering mechanism. Friction pendulum isolation device can provide the re-centering performance, but the residual displacement of such bearings is relatively large. In this thesis, the superelastic property of SMA and friction energy dissipation are considered, and friction bearing conbined with large size SMA coil springs is put forward to form a new type of isolator, which can provide large horizontal shear deformation and dissipate seismic energy.This thesis proposes the SMA spring-friction bearing(SFB) and systematically studies its seismic isolation performance in long span and space grid structures.The study can be employed to provide scientific basis and reference for practical application, which have important theoretical meaning and engineering value. The main contents and results are as follows:(1)The superelastic SMA bar with different ratio between Ni and Ti is studied through mechnical performance test under various working conditions. The optimal ratio between Ni and Ti for superelastic SMA and processing method of SMA bars are obtained. Experimental result (stress-strain curve, phase transformation stress, energy dissipation per cycle, equivalent stiffness, equivalent damping ratio and residual deformation) show that the large diameter SMA materials are suitable for making vibration reduction device with re-centering function.(2)The mechanical performance tests are carried out to study the superelastic behavior of SMA coil spring. The results indicate that such SMA coil springs can be applied to the damper for re-centering control and vibration reduction.(3)From Liang-Rogers classic SMA constitutive model, a new mechanical model of superelastic SMA coil spring is established. The accuracy and reliability of the proposed model are verified in this thesis.(4)The numerical simulation of seismic response of SFB isolation system are performed, and the result show that SFB isolation device between the superstructure and substructure has good acceleration reduction effect. Meantime, the developed seismic isolation device can be used to effectivelly reduce the peak displacement of isolation layer and residual displacement of individual bearing.(5)SFB isolation devices are applied to space grid structure, and the numerical simulation results show that the proposed devices have excellent isolation and control performance.