FRAGILITY CURVE OF SCHOOL BUILDING IN PADANG CITY WITH AND WITHOUT RETROFITTING DUE TO EARTHQUAKE AND TSUNAMI LOADS

SMPN 25 building in Padang City is a junior high school building located in the high seismic zone and prone to tsunamis. Based on the initial analysis of the existing building using the current Indonesian building codes, this building has not been able to withstand the working earthquake and tsunami loads. In this study, the retrofitting of the building was designed using concrete jacketing that is with additional dimensions and reinforcement, aimed at making the building function as a vertical evacuation structure. The structural fragility curve of the building is determined before and after retrofitting for both earthquake and tsunami loads. The fragility curve is determined from the ductility of the building for each variation of earthquake acceleration based on the Hazus standard. The first yield displacement was determined from the pushover analysis, and the ultimate displacement was determined from the time history analysis. The earthquake acceleration records used were the El-Centro earthquake, the Northridge earthquake, the Kobe earthquake, and the Padang earthquake. The results of the analysis show that the retrofit of the building structure using concrete jacketing reduces the probability of damage to the building structure due to earthquake loads by 42.06% at the level of extensive damage and by 4.42% at the level of complete damage at PGA 0.6g, while, it reduces the probability of building damage due to tsunami loads by 45.53% at the level of extensive damage and by 26.32% at the level of complete damage at a tsunami inundation depth of 4.5m.