Comparison of Non-Isolated and Base-Isolated RCC Moment Resisting Framed High-Rise Buildings

Seismic isolation has emerged as an effective strategy for improving the earthquake resilience of high-rise buildings, particularly in seismically active regions such as Nepal. This study investigates the influence of lead rubber bearing (LRB) base-isolation systems on the seismic performance of a fourteen-story reinforced concrete moment-resisting frame by comparing a conventional fixed-base model with a base-isolated model designed and analyzed in ETABS 2021 in accordance with IS 1893:2016, IS 456:2000, and IS 875 using response spectrum analysis. Key seismic response parameters, including the fundamental time period, base shear, lateral displacement, inter-story drift, and floor acceleration, were evaluated, and the results revealed a significant enhancement in the seismic performance owing to base isolation. The incorporation of LRBs increased the fundamental time period by approximately 2.5 times, thereby shifting the structural response away from the dominant ground motion frequencies, which led to a reduction in the base shear of nearly 70%, along with substantial decreases in inter-story drifts, floor accelerations, and top-story displacements. Furthermore, the base-isolated structure requires smaller structural member sizes, indicating improved structural efficiency and effective energy dissipation with controlled flexibility. These findings confirm that LRB base-isolation systems significantly reduce both structural and nonstructural damage during earthquakes and represent a reliable, high-performance seismic mitigation strategy for high-rise buildings, particularly for critical infrastructure and densely populated commercial buildings, where safety and post-earthquake functionality are essential.