Effect of Plan Inclination on Seismic Response on Residential RC Buildings

Abstract

In earthquake prone areas like Nepal, the plan irregularity significantly influences the seismic response of the buildings. This study analyses how progressive inclination of plan influences the seismic performance of the RC residential buildings. Seven analytical models were created: six irregular models with one wall inclined at 5°, 10°, 15°, 20°, 25°, and 30°, and one regular model with parallel lateral load resisting systems (0° inclination). ETABS 2022 was used to analyze all models in compliance with IS 875 for gravity loads and NBC 105:2020. Base shear, basic period, center of mass–center of rigidity eccentricities, story drift, displacement irregularity ratios, and internal forces (shear forces and bending moments) in beams are important response factors taken into account.
The findings indicate that while all storey drift ratios remain well within the Ultimate Limit State (ULS) and Serviceability Limit State (SLS) limits specified by NBC 105:2020, increasing inclination results in a slight increase in fundamental time period and base shear (less than 1% variation between 0° and 30°).The study comes to the conclusion that, when low-rise RC buildings are designed in accordance with NBC 105:2020, minor to moderate plan irregularity does not significantly affect global seismic stability; however, it does change local demand and detailing requirements close to irregular zones. Recommendations for mid- and high-rise buildings and other complex irregularities and nonlinear analysis are given.