Seismic Vulnerability Assessment of Old City Hall Annex Building located at Brgy. Isabang, Lucena City

Due to the Philippines' location within the pacific Ring of Fire, most of its structures are susceptible to earthquakes. Especially those old-age structures that existed way before the seismic code of the Philippines in the NSCP was established. The Annex building was constructed in the year 1995 before the NSCP seismic code was established in 2001. In line with this, seismic assessment is essential for this building due to to it currently being used as an educational establishment of Dalubhasaang Lungsod ng Lucena, for the safety the occupants dwelling in the structure, also it is great help to the national government, community, and people living in and near the locale. The study utilized SAP 2000 and the data for peak ground acceleration gathered from IRIS, the study is done by utilizing a simulation using SAP2000 and initializing pushover analysis, and response spectrum, which results in the creation of a capacity spectrum. In the simulation, the structure was subjected to 20 earthquakes, 10 international, and 10 local. The final output of this study is the probability of occurence per damage state of the structure relates to the ground motion the structure was subjected to in the simulation. The National Structural Code of the Philippines states that structures are designed to withstand a peak ground acceleration of 0.4g. Based on the probability of occurence obtained in this study the annex building is adequate to resist the 0.4g 60%, 5%, and 35% for slight, moderate, and extensive damage respectively having slight damage the most probability compared to the moderate, extensive, and complete damage however, the x-direction is not adequate to resist 0.4g with the probability of occurrence of 20%, 20%, and 60% for slight damage, moderate damage, and extensive damage respectively, slight damage not having the most percentage compared to the moderate, and extensive. The structure, however, may experience severe or complete damage at 2.2g peak ground acceleration. This study provides information on what the structure is lacking in terms of resisting earthquakes in a direction that can help with the retrofitting methods that can be used to improve the structure.