Abstract
Superelastic shape memory alloy (SMA) is a potential candidate for use in structure damping devices due to its unique
mechanical properties. In order to mitigate the vibration of a structure subjected to earthquake tremors from different
directions, an innovative, multi-directional SMA-based damper is advanced. The damper, with two movable cylinders
attached to four groups of SMA strands arranged in a radial symmetry, can not only function in a plane, but also can
work vertically and rotationally. Based on experimentation, the Graesser model of superelastic SMA is determined. By
analyzing the damper's mechanism working in different directions, the corresponding theoretical models are developed.
Numerical simulations are conducted to attain the damper's hysteresis. Working in a plane, the damper, with a 3%
initial strain, provides a rectangular hysteresis with the maximum amount of damping. A rectangular flag hysteresis can
be supplied in the absence of a pre-stress in the wires, going through the origin with a moderate amount of energy
dissipation and higher force capacity. Moreover, the damper has better working capacities (i.e. force, stroke and energy
dissipation) if the deflection is parallel to the internal bisectors of the tension axes. Working vertically or rotationally,
similar triangular flag hysteresis is generated with small energy dissipation and a self-centering capacity. For a given
deflection, the initial strain (3%) increases the force of the damper, but decreases its stroke.
