Numerical Simulation And Engineering Application Of Self-centering SMA Dampers

For shape memory alloys (SMAs) in their austenitic state, stress induced martensitetransformation occurs upon loading, resulting in large deformations. Reverse transformationsfrom martensite to austenite occurs when withdrawing applied loads. This results in thealloys restoring their initial shape. This is called the super elastic effect of SMA. Manytypes of SMA based self-centering dampers were presented recently with using superelasticity,and some dampers were applied in the real conditions. When using the self-centering SMAdampers for vibration controlling during earthquake event, there are no needs for outer energyinputs and no residual interstorey drifts. This attracts more attentions of the engineers.To extend the applications of the SMA damper, this paper investigates the numeralsimulations of the mechanical behavior of the SMA damper by programing in MATLABenvironments based on the material constitutive models. Moreover, the vibration controleffects of the SMA damper are evaluated by time history analysis of passive structures. Theworks of this paper are listed in details as follows:1. The superelastic behavior of SMAs are introduced. The tensional experiments of1mm diameter NiTi SMA wires were conducted, and the effects of loading rate, strainamplitude and loading cycles on superelasticity are studied. The evolution process of severalphenomenologital constitutive models are introduced. Among these models, the Brinsonconstitutive model is selected to describe the strain-stress relationship of the superelastic SMAby programming in MATLAB environments. Good agreement between the experimental andnumerical results is observed.2. The configurations are introduced and summarized based on three types ofself-centering SMA dampers. These dampers consists of two functional groups, recentring andenergy dissipating groups. The damper working principle is studied by figuring out theinternal force changement with relative displacement of both ends of the damper. For theSMA damper with springs offering restore force and two groups of SMA wires dissipatingenergy, the force equilibrium equations are presented. With using the Brinson model, theforce-displacement relationships of the damper are described by programming in MATLABenvironments.3. For a three-storey steel frame equipped with the SMA damper, the structural responseis simulated by time history analysis program in MATLAB environments based on materialconstitutive model. The simulation is conducted as follows: The main frame is simplied as a inter-story shearing structure. Then, the mass, stiffness matrix together with the dampingmatrix of the main structure are presented. The dynamic equations with considering thecontrolling force offered by the SMA damper are founded. With using Wilson-θ method, theequations are solved and the structural responses are simulated by time history analysisprogram in MATLAB environments. The earthquake waves, such as El-Centro(NS)、Northridge(NS) and Taft waves, are selected as earthquake excitations, the structuralresponses including inter-storey drift, floor accelerations, inter-storey shear force withconsidering the damper effect are contrasted with those without the damper.4. To assess the vibration control effect of the SMA damper, the Benchmark structuresare analyzed as follows: For high, medium and lower Benchmark frames, the finite elementmodels are set up in SAP2000environments, the structural responses with equipped the SMAdamper and without the damper are contrasted. The vibration control effects of the damper areevaluated. In addition, the SMA dampers was applied to strengthen a6-storey frame. Thestructural vibration control effects are analyzed with considering the damper distributions...