Exploring seismic resilience of multi-story isolated structures: A comparative analysis of triple and quintuple friction pendulum isolators

This study conducts a 3D comparison of Triple (TFPI) and Quintuple (QFPI) Friction Pendulum isolators for a six story steel building. Its key innovations are two-fold: first, a performance comparison based on optimally designed isolators with closely matched parameters (such as effective period, effective stiffness, etc.); and second, the novel use of a hybrid design method integrating Capacity Spectrum Analysis with the Equivalent Lateral Force (ELF) procedure for the isolator design. The superstructure was designed in accordance with ASCE/SEI 7-2016 and models developed in SAP2000 were validated against OpenSees and literature. Analysis under seven bidirectional far-field records on stiff soil showed QFPI’s superiority, reducing story acceleration and shear by an additional 34% and 30% versus TFPI. While both isolators controlled drift comparably, QFPI achieved this with a 3.5 times more compact design and fewer constraints, demonstrating greater efficiency and practicality.