Comparative quasi-static analysis of the seismic performance of Piloti-type RC structures with and without seismic isolation

As the state-of-the-art in seismic resilience evolves from basic life-safety toward damage mitigation and continuous functionality, piloti-type reinforced concrete (RC) buildings remain a critical vulnerability due to their inherent vertical irregularities. While extensive literature addresses general soft-story retrofits, few studies detail the specific plastic hinge evolution and directional isolator–column interactions required to optimize isolation strategies. To bridge this gap, this study evaluates a representative piloti-type RC prototype (Ministry of Land, Infrastructure and Transport, R.O.K.), explicitly selected because its mid-rise height, asymmetric wall layout, and column dimensions accurately represent the broader stock of vulnerable piloti structures. To ensure strict methodological reproducibility, including ASCE-41 plastic-hinge definitions, material nonlinearity parameters, and effective section properties, all modeling choices are comprehensively detailed in SAP2000. Also, distinct from dynamic earthquake simulations, this study employs displacement-controlled quasi-static analyses to systematically map capacity and collapse progression without ground motion variability. Comparative analyses in both principal directions for non-isolated and base-isolated (lead-rubber bearing) configurations reveal that the non-isolated frame develops collapse-level softstory hinges at low displacements. On the other hand, the base-isolated model completes the prescribed displacement history without collapse by dissipating input energy through isolator hysteresis, dramatically reducing superstructure hinge demand and standardizing the inter-story drift profile. Differentiating this work from prior research, the results highlight that directional stiffness disparities and column sizing dictate energy absorption pathways as larger column sections and higher-stiffness axes significantly enhance isolator efficiency. The findings in this study provide novel, reproducible insights into typical piloti-type RC structural interactions, offering practical guidance for performancebased design in high-density urban seismic regions.