SEISMIC ANALYSIS OF DAMAGED BUILDINGS BASED ON POST-EARTHQUAKE INVESTIGATION OF THE 2018 PALU EARTHQUAKE

On September 28, 2018, Palu city in the Central Sulawesi area, suffered the M7.5 earthquake. An epicenter of its earthquake located 77 km from the capital of Central Sulawesi Province, Palu city. The main earthquake, followed by a localized 4 to 7 meters high tsunami, which swept shore-lying houses and buildings on its way. A large number of damages on reinforced concrete (RC) buildings, houses, and soil liquefaction spread in Palu city were observed after the earthquake. The post-earthquake observation, as is reported in this paper, was conducted in order to define the typical pattern of the buildings' damages. The field investigation was focused on the damaged RC frame of buildings' structures. Several types of damage were detected on RC structures such as collapse due to the soft story, damage to beam-column joint, failure of short column, shear failure of the column, and collapsed of brick masonry infills. Two damaged RC frame buildings, i.e., one was severely damaged and the other in totally collapsed, were furthermore analyzed to define their seismic capacity based on Japanese standard. According to the analyses of the first story in these buildings, the distinct difference of seismic performance of both buildings was discovered. The severely damaged building had a higher lateral strength index when compared to the collapsed building because of its structure able to maintain the lateral strength within large deformation.