Seismic Vulnerability Assessment of Existing Buildings: A case study of Senate Building in Makerere University

This study evaluated the seismic vulnerability of existing buildings at Makerere University with focus on Senate Building as a representative structure for mid-rise buildings in the University. Despite Uganda’s classification as a low seismic zone, historical earthquakes have exposed significant infrastructure vulnerabilities particularly in educational institutions. The lack of specific locally calibrated models for assessing seismic risk, coupled with the varied and often vulnerable nature of existing construction and limited seismic data in Uganda, makes predicting the seismic vulnerability of existing buildings challenging thereby creating a critical gap in disaster preparedness. The research employed a quantitative methodology combining building inventory classification, structural modeling and fragility curve development. Nonlinear static pushover analysis using SeismoStruct assessed structural capacity and also produced eigenvalue results which enabled identification of ductility limitations. Ground motions from the PEER NGA database were scaled to a target spectrum for Kampala from the GEM framework. Fragility curves were developed using the Capacity Spectrum Method and they quantified the probability of exceeding limit states. Results indicate that Senate building has a total base shear of 4800 kN thereby resisting more lateral force before failure than high rise buildings. However, Senate building reaches the Significant Damage limit state at lower drift values when compared to high rise buildings thereby suggesting brittle behavior. Results also indicate that Senate Building showed moderate resilience reaching the Near Collapse limit state at 0.56g. These findings highlight the urgent need for retrofitting existing buildings in Makerere University particularly for mid-rise buildings and advocate for updating the current seismic code to address seismic vulnerability assessment of existing buildings. This research provides a framework for seismic risk analysis in Ugandan thereby informing retrofitting strategies, policy development, and emergency planning for existing buildings. It bridges a critical gap in regional seismic vulnerability assessments and contributes to global earthquake engineering practices by highlighting the importance of tailored vulnerability evaluations for older building stocks. Keywords: Seismic Vulnerability, Capacity curves, Fragility Curves