Comparative Seismic Analysis of Multi-Story RC Buildings under the Indonesian Seismic Code Using Static Equivalent and Response Spectrum Methods

Indonesia’s geographic position along the Pacific Ring of Fire exposes it to frequent and potentially devastating seismic events, necessitating reliable analytical methods for earthquake-resistant structural designs. While seismic design codes such as the Indonesian Seismic Code permit both linear static and dynamic analyses, the practical differences between the Static Equivalent Method (SEM) and Response Spectrum Analysis (RSA) remain insufficiently explored for multi-story Reinforced Concrete (RC) buildings. This study addresses this gap by comparing the seismic responses predicted by SEM and RSA for regular RC moment-resisting frame structures with two, four, six, and eight stories. Structural modeling and analysis were conducted using ETABS, and the evaluation focused on the key response parameters, including the total base shear and story-level seismic force distribution. The results indicate that RSA consistently predicts a higher base shear than SEM, with the discrepancy increasing as the building height increases. Additionally, the RSA captures a more dynamic and non-uniform seismic force distribution along the height, particularly in mid-level stories where the higher-mode effects become significant. These findings highlight the limitations of SEM in representing the dynamic behavior of taller structures and emphasize the suitability of RSA for more accurate seismic demand estimation in the performance-based design of mid- to high-rise RC buildings in seismically active regions.