<![CDATA[Structural irregularities significantly affect the seismic performance of buildings, especially in high-risk earthquake zones. This study aims to analyse the influence of plan and vertical irregularities on structural response parameters, including lateral forces, shear forces, overturning moments, inter-story drifts, and fundamental periods. The object of study is a ten-story U-shaped reinforced concrete office building, modelled using ETABS software. Two structural systems are compared: the Special Moment Resisting Frame (SMRF) and the Dual System (a combination of SMRF and shear walls). The analysis follows the linear response spectrum method based on the Indonesian seismic code SNI 1726:2019. The results indicate that structural irregularities increase the concentration of internal forces and displacements in critical structural components, raising the potential for localized failure. The Dual System demonstrates better performance in controlling deformation and distributing seismic loads more evenly compared to the SMRF system is 20 percent. These findings highlight the importance of selecting an appropriate structural system and accounting for irregularities early in the design process to enhance seismic resilience.]]>
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