Assessing the Seismic Vulnerability of Buildings in Patan Area, Nepal

This study presents a comprehensive seismic vulnerability assessment of diverse building typologies in Patan, Nepal, a region characterized by high seismicity and significant architectural heritage. The investigation focused on Reinforced Concrete (RCC) residential and commercial structures, traditional brick masonry buildings, and a monumental heritage structure (Vishwanath Temple). A hybrid methodology was employed, integrating advanced numerical modeling techniques (ETABS for RCC, DIANA FEA for masonry) with empirical material testing and a heuristic approach for the monumental building. Nonlinear static (pushover) analyses were performed to determine structural capacity, identify failure mechanisms, and evaluate performance points under incremental lateral loading. Fragility curves were subsequently developed using HAZUS guidelines to quantify the probability of exceeding specific damage states (slight, moderate, extensive, and collapse) across varying seismic intensities. Findings indicate that RCC structures generally exhibit ductile behavior, though the commercial building showed higher strength with yielding at larger displacements compared to its residential counterpart, and demonstrated potential for extensive damage or collapse at moderate-to-high PGA values (performance near collapse around 0.18g PGA). Traditional brick masonry buildings displayed characteristic brittle behavior, marked by limited displacement capacity and significant post-yield strength degradation, particularly in the X-direction. This typology exhibited high vulnerability, with probable collapse under seismic events exceeding 0.21g PGA. The heuristic assessment of the monumental heritage structure also revealed high vulnerability, with a significant likelihood of slight damage at low PGA levels and substantial damage at moderate to high PGAs. This research provides critical, typology specific seismic vulnerability data, offering valuable insights for informing risk-sensitive urban development, retrofitting prioritization, and disaster preparedness strategies in Patan.