Seismic Performance of Reinforced Concrete Buildings in the 2021 Mamuju-Majene Earthquake Mw. 6.2, Sulawesi Indonesia

Abstract The seismic performance of RC buildings in Mamuju in West Sulawesi of Indonesia during the 2021 Mamuju-Majene earthquake is examined. Despite the earthquake's recorded acceleration being just 0.26 g, or 25% of the predicted acceleration (1.027 g), it has resulted in the collapse of many RC buildings across the city of Mamuju. We conducted a post-earthquake investigation to uncover the mechanism of collapsing RC buildings, with the aim of learning lessons and gaining insights for improvement in RC building design. Extensive geotechnical and geophysical investigations reveal the ground motion in the city reached 0.68 g, or about 66% of the anticipated ground motion specified for the city of Mamuju on the provision of the Indonesia Code (SNI 1726-2019). This observation suggests that the traditional design of the current RC buildings may perform seismically poorly. Therefore, elastic linear modal analysis and non-linear static and dynamic analysis were conducted to uncover the failure process of the RC building during the earthquake. The results reveal that the collapse of the RC building starts with the formation of plastic hinges at the column members on the ground floor, whereas the column members on the first and second levels remain in an elastic state. Under these circumstances, the RC building's roof displacement exceeded the critical displacement for collapse prevention. For future prevention, a revised structural design has been suggested to enhance the seismic resistance of the RC building with target performance following the Indonesia Code SNI 1726-2019. Increasing the cross-section area of the column members of RC building over a fixed base foundation can result in a more rigid structure and a lower inter-story drift ratio.