Proposed SMA Tension Sling Damper for Passive Seismic Control of Building

Passive Shape Memory Alloy (SMA) based Tension Sling Damper (TSD) is proposed to control seismic response of building represented as dynamic SDOF system. Non-linear hysteretic behavior of SMA is characterized by Tanaka model with seismic excitations as input. It is converted to equivalent piece-wise linear elastic viscous damping model described by stiffness constant 'k(eff)'and damping constant 'c(eff)' to implement it with linear dynamic system. Damping constant 'c(eff)' is evaluated for TSD for given seismic excitation at each instance of time defined as instantaneous damping, unlike constant damping used in other studies, to derive accurate seismic response of the dynamic system. Seismic response control parameters - peak and rms performance indices (PI) for displacement and acceleration, peak damper force, maximum damping ratio are evaluated for flexible, moderately stiff and stiff dynamic systems fitted with TSD under pulse and strong ground motion type seismic excitations with varied PGA. Substantial reduction in PI is observed for controlled systems through varying design parameters of TSD - cross-sectional area and length of SMA sling. TSD yields better seismic response control for moderately stiff and flexible system due to super-elastic properties of SMA. Further, it works efficiently for seismic excitations with low to moderate PGA.