Effect of Shear Wall Configuration on Torsional Response and Seismic Performance of Irregular Buildings

[EN] Indonesia lies in a region of high seismic intensity, so earthquake-resistant design is essential for buildings in high-risk categories. This study evaluates the seismic performance of the Public Service Building (GLU) of Institut Teknologi Sumatera (ITERA), a seven-story reinforced concrete building with an irregular plan, classified as Risk Category IV, under five shear wall placement configurations: SWC-Full, CW-Only, SW-Only, SWC-Dist and SW-Multi. The structure was modeled in ETABS as a dual system and analyzed using response spectrum analysis in accordance with SNI 1726:2019 and nonlinear static pushover analysis based on FEMA 440. Seven parameters were assessed: structural period and modal response, inter-story drift, P-Delta stability, dual system effectiveness, element compliance with the Special Moment-Resisting Frame (SMRF) requirements of SNI 2847:2019, shear wall capacity, and pushover performance level. The results show that the centralized configuration (SWC-Full) produces a dominant torsional first mode (RZ), whereas the distributed configuration (SWC-Dist) produces a translational first mode (UX). The X-direction period ranges from 0.876 s (SWC-Dist) to 1.673 s (SW-Only). Only SWC-Full and SWC-Dist satisfy all seven evaluation criteria simultaneously, with drift-based performance levels between Immediate Occupancy (IO) and Life Safety (LS) and practically equivalent relative scores (0.92 and 0.90). Removing the core wall (SW-Only) causes drift and beam failures, including a 42% exceedance of beam flexural strength, and leaves the walls only 13% of the X-direction base shear. These findings indicate that, for irregular Risk Category IV buildings, the shear wall–core wall combination is the decisive factor in satisfying the seismic requirements.