Effect Of Column Orientation on Structural Performance of Irregular RC Building Using Pushover Analysis

This study evaluates the effect of rectangular column orientation on the structural performance and collapse mechanisms of reinforced concrete buildings with horizontal irregularities. The analysis used nonlinear static (pushover) analysis based on SNI 1726:2019 and ATC-40 on an eight-story office building model in Pejaten, South Jakarta, characterized by torsional irregularity, re-entrant corners, and diaphragm discontinuity. Three structural models were developed with different column orientations: Model I with the strong axis oriented in the Y-direction, Model II in the X-direction, and Model III with combined X and Y orientations. The results indicate that Model I provides the most balanced structural response, with displacement ranging from 0.498 mm to 3.959 mm, significantly lower than Model II, which reaches up to 74.417 mm, and Model III, which reaches up to 33.684 mm. Model I's inter-story drift ratio is approximately 0.2%, compared with 0.7% in Model III and 1.9% in Model II, indicating a substantial difference in structural performance. Model I achieves a beam-dominated collapse mechanism, while Models II and III exhibit column-sway or soft-story mechanisms. These findings confirm that column orientation significantly influences stiffness distribution and seismic performance in irregular buildings. Aligning the column strong axis with the structurally weaker direction is therefore recommended to improve structural stability, control lateral deformation, and achieve a more desirable collapse mechanism.