Abstract
Structural irregularity is a factor that can significantly affect a building's response to seismic loads. Therefore, an analysis that more realistically represents structural behavior under earthquake excitation is required. This study aims to analyze the irregularity of a reinforced concrete structure in an eleven-story hotel building with a height of 48 m located in Pontianak City using the linear time-history analysis method. The earthquake ground motion records employed in this study were obtained from the Imperial Valley, Morgan Hill, Whittier Narrows, and Chichi earthquakes. Structural modeling and analysis were performed using RSAP (Robot Structural Analysis Professional) 2024 and SeismoMatch in accordance with SNI 1726:2019 and SNI 2847:2019. The structure uses a reinforced concrete Special Moment-Resisting Frame (SMRF) system and considers Site Class SE and seismic design parameters of SDS = 0.281 g and SD1 = 0.143 g. The maximum interstory drift was found to be 44.836 mm under the Morgan Hill Y (-) case, corresponding to a base shear of 813.887 kN. The structure exhibited Horizontal Irregularity Types 1a and 1b, with the most critical condition caused by the Chichi X (+Y) case. The minimum ratio of story lateral strength was found to be 99.369% on the 10th floor; therefore, the structure does not exhibit Vertical Irregularity Type 5b. The results indicate that structural irregularities significantly influence the seismic performance of the building and should be carefully considered in the design and evaluation of reinforced concrete structures subjected to earthquake loads.