The impact of plan irregularity on multistory building response: A pushover analysis

Abstract

Structural irregularity often stems from a combination of plan and elevation irregularities, as perfect regularity is seldom achieved in real structures. Defining structural irregularities is challenging due to their varying nature. While scientific literature tends to separate plan and elevation irregularities, there's a need to understand the behavior of real structures that possess plan irregularities. This paper investigates the impact of plan irregularities on multi-story building responses through pushover analysis. The study aims to evaluate various parameters such as capacity curves, performance levels, story drifts, and displacements for irregular building models compared to regular ones. Four and eight-story buildings are designed according to Indian standards, and nonlinear static analysis is conducted using a plastic hinge model. Plastic hinges are assigned at possible failure locations, and pushover analysis is performed. Eccentricity is incorporated by shifting the position of live loads and adjusting column dimensions on both sides of the axis of symmetry at eccentricity values of 10%, 20%, 30%, and 40%. Displacement-controlled pushover analysis is conducted, and pushover curves are obtained in the X direction. The performance of building models is compared with a regular reference frame. Capacity curves, performance points, and story response plots are analyzed using ETABS 9.7.0. The results indicate a reduction in base shear capacity with increasing irregularity, with eccentricity showing a greater effect than soft story irregularity. Irregularity also influences the height-wise variation of story drifts differently.