Influence of Mass Irregularities on the Seismic Behavior of Multi-Storied Using STAAD.Pro Connect Edition

The seismic behavior of multi-story buildings is greatly influenced by their structural configuration. Irregularities in plan or elevation, particularly mass irregularities, are critical factors contributing to structural failure during earthquakes. Proper identification and management of such irregularities are essential to optimize a building's functionality and aesthetics. This study examines the seismic response of a G+14 reinforced concrete (RC) frame structure with and without mass irregularity. The analysis focuses on storey drift, storey displacement, lateral loads, maximum bending moments, and shear forces. A swimming pool placed on the 7th floor introduces a heavy mass, creating mass irregularity as per IS 1893 (Part 1):2016, where a floor’s seismic weight exceeds 150% of the floors above and below. Using STAAD.Pro Connect Edition software, the structures are analysed through dynamic response spectrum analysis. The residential building, with dimensions of 35.45 m × 30.56 m, is subjected to seismic loads according to IS code standards. Results indicate that the inclusion of mass irregularity significantly impacts the seismic response, leading to notable variations in drift, displacement, and internal force distribution. This study highlights the importance of addressing mass irregularities in seismic design to ensure structural safety and performance in earthquake-prone areas. Keywords: Mass irregularity, seismic response, RC frame, STAAD.Pro, storey drift, response spectrum, IS 1893:2016, dynamic analysis.