Comparative analysis of response of BI building with varying post yield stiffness ratio under NF and FF ground motion

Abstract

This study aims to examine the performance a base-isolated (BI) building with varying post-yield stiffness ratio (PYSR) to near-field (NF) and far-field (FF) ground motion in scaled and unscaled forms. The PYSR was varied as 0.05, 0.10, 0.15, 0.20, and 0.20. The ground motions were scaled to Zone IV as per IS 1893: 2016 (Part 1). Time history analysis was performed for various cases of the building and responses- storey displacement, IDR, storey acceleration and base shear were determined. It was found in the study that Lower PYSR (0.05) provides maximum isolation efficiency with minimum base shear and IDR and higher energy dissipation, but results in greater displacement demand. Higher PYSR values (0.20–0.25) increase force transmission with only marginal improvement in acceleration control, showing diminishing benefits beyond PYSR 0.15–0.20. NF ground motions produced higher force, and displacement demands due to pulse-type effects, making them critical for displacement-based design, whereas FF motions exhibited smoother responses and greater sensitivity to PYSR variation. An optimal PYSR range of 0.10–0.15 was found for NF ground motions while 0.10–0.20 was found to be suitable for FF ground motions, ensuring a balanced displacement control, force reduction, and energy dissipation.