New SMA Damper And Application For Seismic Reduction And Control Of Structures

The damper's damping performance is the most important factor. In order to get a good seismic control device for structure, Shape memory alloy is studied. Fist, Experiments on the mechanical behaviors of super elastic NiTi shape memory alloy wires have been finished in this paper. Second, based on the material experiments, a new damper, which stiffness and damp can alter, is developed. Last, the simulation analysis on seismic response of three-floor frame and long-span bridge with SMA damper, results show that this kind of SMA damper can availably suppress the seismic responses of structure. The main contents and achievements in this paper are as follows.(1) Experiments on the mechanical behaviors of super elastic NiTi shape memory alloy (SMA) wires have been finished in this paper. Temperature, strain rate, strain amplitude, cyclic number and pre-strain were considered as loading conditions to investigate the effects of them on the mechanical parameters of SMA such as phase transformation stress, energy dissipation and effective stiffness. Based on the above experimental results and the general SMA constitutive models, a simplified constitutive model has been set up. Using the model to simulate the tension behaviors of super elastic SMA, the results match well with experimental results.(2) Based on the simplified constitutive model and the behavior of shape memory alloy, the relations between energy dissipation and pre-strain, maximum strain, stiffness and length of SMA were studied. The results obtained are important for us to design SMA damper.(3) A new SMA damper, which stiffness and damp can alter, is developed. Experiments on the SMA damper have been finished. Strain rate and strain amplitude were studied to investigate the effects of them on the mechanical parameters of SMA such as damper stiffness, output control force and energy dissipation. Based on experimental results of SMA damper, a mechanical model has been set up. Some key parameters'expressions are also presented.(4) A fuzzy controller is designed in this paper. The damper stiffness and damp are altered through the fuzzy controller. The input-output results of fuzzy controller show that the fuzzy controller can availably and accurately determine the number of working groups of SMA wires.(5) The simulation model is built by using the fuzzy control toolbox and the Simulink block in MATLAB, and the seismic responses of a three-story frame structure in the case of fuzzy control are carried out. The results show that the SMA damper with fuzzy controller can availably suppress the displacement, velocity and acceleration of structure. The control effect is closed with active control effect. So the fuzzy control system with SMA damper is a reliable smart control system.(6) The simulation analysis on seismic response of seven continuous rigid-framed bridges at the two states of SMA dampers control, restrainer control, was carried out. The results show that this kind of SMA damper can availably control the seismic displacement of bridge, whose control effect for expansion joint's displacement is better than steel restrainer.