A Modified Framework for Seismic Fragility Assessment of School Buildings in High-Intensity Seismic Zones of Pakistan

Abstract

The current research is targeted to develop analytical fragility curves for school buildings in seismic zone 4 of Pakistan. Data was collected from Muzaffarabad, Poonch, and Neelam Districts from Azad & Jammu Kashmir region that has been categorized as high-intensity seismic zone in Building Code of Pakistan. 2417 schools were visited and three building typologies; Reinforced Concrete (RC) schools, Stone Masonry schools, and Brick Masonry schools, were defined accordingly. RC schools comprised 79% of total school building stock in considered districts. On the other hand, stone masonry schools were mostly found to be abandoned, while brick masonry schools were mostly opened in houses by small-scale investors, lacking spirit of an educational facility. A new framework has been proposed and demonstrated in current research for assessing seismic fragility of RC school buildings. Developed methodology considers uncoupled modes of structure, employing nonlinear single degree of freedom structures and defines distinct limit states for each mode separately. By using presented methodology, response of higher modes was incorporated in fragility curves. For elucidation, a two-story RC school building structure was selected from seismic zone 4 of Pakistan. Presented methodology reduced computational time required for developing fragility curves of considered school building, using a regular computer. Presented methodology had been validated for its efficacy by applying it to two other case studies; a benchmark structure, developed by Pacific Earthquake Engineering Research Center, and a high-rise building with substantial modal contribution from higher modes. It has been inferred that established methodology is generic and can be conveniently employed to assess structural vulnerabilities of all sorts of RC buildings, subjected to any mixed use. Presented methodology inherently considers the effect of higher building modes in structural response and utilizes Uncoupled Modal Response History Analysis. For determining seismic fragility of stone and brick masonry schools, conventional methodology has been followed that focuses on response of fundamental mode only. Obtained results from proposed methodology prove effectiveness and simplicity of established methodology for determining seismic vulnerability with accuracy.