Seismic Fragility Characterization of Grid-Like Frame Structures

Abstract

Historically, the design of reinforced concrete (RC) moment-resisting frames in regions of moderate seismicity, such as Malaysia, has been predominantly governed by gravity load requirements, which renders a considerable portion of the existing building stock vulnerable to earthquake-related risks. This study presents a parametric seismic fragility assessment of low-rise reinforced concrete (RC) grid-like frames, representative of structures in Malaysia where design has traditionally emphasized gravity loads. A suite of building archetypes was developed to capture systematic variations in key structural and geometric parameters, including plan configuration, story height, bay aspect ratio, column and beam cross-sectional area. Each archetype was subjected to Incremental Dynamic Analysis (IDA) using nine ground motion records from the PEER NGA-West2 database. Peak Ground Acceleration (PGA) was employed as the intensity measure, and maximum interstory drift ratio (MaxIDR) was adopted as the engineering demand parameter. Fragility functions were constructed for five predefined damage states specified by international seismic performance guidelines, ranging from Slight Damage to Collapse. Results indicate that archetypes with smaller member sizes and more rectangular bay layouts (lower aspect ratios) exhibit a significantly higher probability of extensive damage at lower shaking intensities. The proposed framework which comprises a fragility catalog for detailed risk evaluation and a computationally efficient regression model for rapid vulnerability screening—provides a valuable tool for seismic risk assessment, disaster mitigation planning, and prioritization of retrofitting strategies in Malaysia and similar regions.