RETROFITTING OF ULAK KARANG SHELTER BUILDING IN PADANG CITY, INDONESIA, USING CONCRETE JACKETING

Abstract

Padang City is highly vulnerable to earthquake and tsunami hazards due to its location along the subduction zone of the Indian and Eurasian plates. To address evacuation challenges, the government constructed the Ulak Karang Shelter as a vertical tsunami evacuation facility. However, this structure was not originally designed to withstand tsunami loads. This study evaluates the structural performance of the shelter and proposes retrofitting using the concrete jacketing method. The research involved field surveys, collection of technical data, and structural modeling using ETABS v22. The analysis was based on Indonesian building codes (SNI 1726:2019, SNI 2847:2019, and SNI 1727:2020) and FEMA P-646 tsunami guidelines. The results of the structural analysis revealed that some columns and beams lacked sufficient capacity to withstand the combined loads of earthquakes and tsunamis, indicating critical structural weaknesses. After retrofitting with concrete jacketing, the moment capacity of the columns improved by 151%, axial capacity by 106%, and shear capacity by 45%, while beam strength increased by 181% in flexure and 68% in shear. Furthermore, structural displacement was reduced by up to 36% in the X direction and 22% in the Y direction. These findings confirm that concrete jacketing is an effective retrofitting method, enabling the Ulak Karang Shelter to function safely as a vertical tsunami evacuation facility.