Near-Fault Ground Motions and Structural Fragility: Insights into Damage Progression and Collapse Prevention

Abstract

This study investigated the seismic performance of reinforced concrete (RC) structures under near-fault and long-duration ground motions using a performance-based evaluation framework. Numerical analyses were conducted to quantify structural responses, including inter-story drift ratios, plastic hinge formation, residual deformations, and performance-level exceedances at Immediate Occupancy, Life Safety, and Collapse Prevention levels. Near-fault ground motions were found to produce the highest peak drifts and the largest number of plastic hinges, particularly in lower stories, indicating significant damage concentration and reduced post-earthquake functionality. Long-duration motions generated moderate peak responses but caused cumulative inelastic deformation, demonstrating that extended shaking duration can substantially affect residual drifts and long-term structural resilience. Far-field motions produced the lowest response demands, suggesting that conventional code-based design spectra may underestimate structural vulnerability in near-fault regions. Residual drift analysis revealed that even when collapse was avoided, near-fault and long-duration excitations could cause irreparable damage, emphasizing the importance of evaluating post-earthquake usability. Performance-level exceedance analysis further confirmed that near-fault motions considerably increased the probability of surpassing Life Safety and Collapse Prevention thresholds. The findings highlight the necessity of incorporating near-fault characteristics, duration effects, and performance-based assessment in seismic design to ensure damage control, resilience, and occupant safety. These results provide critical guidance for engineers and policymakers in enhancing the seismic robustness of RC structures in earthquake-prone regions.