Investigating the Influence of Vertical Irregularities on Structural Integrity

Abstract

Earthquakes are among the most destructive natural hazards, and structural failures during strong seismic events have demonstrated the vulnerability of buildings with irregularities. This research investigates the influence of vertical irregularities on reinforced concrete (RC) buildings, including stiffness irregularities (soft storey), vertical geometric irregularities (setbacks), mass irregularities, and combined irregularities. Using SAP2000, a series of 19 models—both with and without infill walls—were developed and analyzed under seismic loads following IS 1893 (Part 1):2002 and IS 456:2000. The study applies linear static analysis, nonlinear static pushover analysis, and linear dynamic response spectrum analysis to evaluate seismic performance. Results highlight the critical impact of soft storey and setback irregularities on displacement, base shear, and hinge formation, while infill walls are found to significantly enhance performance. The findings emphasize the need for careful consideration of vertical irregularities in seismic design and suggest directions for improving resilience in earthquake-prone regions.