Seismic Performance of Piloti RC Structures under Full and Selective Lead-Rubber Bearing Isolation Based on Quasi-Static Analysis

Piloti reinforced concrete (RC) structures are prevalent in high-density urban environments due to the spatial efficiency of their open ground stories. However, including the 2017 Pohang earthquake, such seismic events have highlighted the acute vulnerability to soft-story mechanisms and devastating ground-level shear failures. Although conventional retrofits predominantly employ stiffening techniques, the implementation of base isolation via lead-rubber bearings (LRBs) remains largely underexplored due to the prohibitive installation and lifecycle maintenance costs. Based on the description above, this study evaluates the seismic performance of a typical Korean piloti RC structure through quasi-static analysis in SAP2000. Four distinct configurations are comparatively investigated: a conventional fixed-base structure (CASE-1), a fully isolated structure utilizing LRBs under all base columns (CASE-2), and two theoretically economical selective isolation schemes (CASE-3 and CASE-4) designed to protect specific core and non-core regions. By analyzing the state of plastic hinges, structural performance, and responses, including structural lateral displacement, drift, LRB behavior, story behavior, and cumulative energy dissipation, this study evaluates the mechanical efficacy of varying seismic isolation designs. The findings reveal that selective LRB configurations are inherently detrimental to the structural integrity of piloti buildings, contrary to the anticipated practical compromise. The analytical results note that the partial isolation exacerbates seismic vulnerability by reducing the number of vertical elements actively resisting lateral loads rather than achieving the intended mechanical decoupling, thereby amplifying the shear burden. This results in substantially higher base shear at equivalent lateral displacements, greater cumulative energy dissipation, and the premature progression of plastic hinges into the collapse (C) state. An analytical structural performance in this study demonstrates that full isolation (CASE-2) is optimal, followed by the conventional fixed-base structure (CASE-1), with the selective schemes ranking worst. In conclusion, this study serves as a valuable reference for the following research, proving that partial base isolation is flawed and underscoring the absolute necessity of full base isolation to ensure structural resilience.