Fragility Assessment of Base-Isolated Structures With Lead Rubber Bearings and Natural Rubber Bearings Equipped With Shape Memory Alloy

Seismic isolators and Shape Memory Alloys (SMAs) are respectively examples of successful passive systems and desirable materials in control systems which improve the performance of stuctures. SMAs have some features such as the ability to withstand large strains without much leaving residual strains, high fatigue and corrosion resistance, and high energy dissipation. These properties makes this material appropriate for utilizing in isolators. The aim of this study is to evaluate the effect of using SMA wires or cables in improving the efficiency of Natural Rubber Bearings(NRB). Initially, 3 groups of steel SMRF structures, 3,6,9-story buildings, isolated with Lead Rubber Bearings(LRB) have been designed. Subsequently, their isolators were replaced with NRB isolators equipped with SMA Cables in shear deformation, and buildings are analyzed under sensitivity analyses with the participation of different stiffness values of isolators components. Results indicate the fact that performance indices have been improved with participation of SMAs in NRB isolators. Then, the participations of SMAs in NRB isolator were optimized. Finally, structures with the aforementioned isolator and the LRB isolator have been analyzed under incremental dynamic analysis and compared according to the fragility curves. These results reveal the better performance of isolator equipped with SMAs in reducing the probability of the superstructure failure in minor to extensive damage states. The introduced isolator has performed slightly weaker in controlling isolation damage states in comparison with conventional LRB isolators. However, the overall performance is Justified due to it s self-centering property.

Keywords:

Base-isolation system , Shape memory alloy , Fragility curve