Seismic Performance of a Heritage School Building Retrofitted with Various Techniques

This study focuses on evaluating the performance of an aged heritage building made of unreinforced brick masonry under seismic conditions, both with and without retrofitting. To achieve this, an experimental examination was conducted using a scaled-down model of a single-story unreinforced building, constructed on a shake table at a 1:4 geometric scale. The responses of this model were recorded at the roof level, primarily in the form of displacements. Subsequently, the same scaled model was replicated in SAP2000 finite element (FE) software. The results obtained from the FE model closely matched the experimental findings, validating the computational approach. Following this validation, an existing masonry heritage school building situated at Aligarh Muslim University, Aligarh, was chosen for further investigation. In this subsequent analysis, natural frequencies and mode shapes were computed through model analysis, revealing closely spaced natural frequencies. To assess the seismic performance of the heritage building, a nonlinear time history analysis was conducted using actual ground motion data from the Koyna earthquake. The maximum compressive and tensile stresses generated numerically under both gravity and earthquake loading conditions were compared with permissible stresses in accordance with Indian masonry standard codes. The finite element model demonstrated that the building remains structurally sound under gravity loading, although some vulnerable areas were identified under earthquake loading conditions. To mitigate the stresses in these vulnerable zones, various retrofitting techniques were explored. Notably, the application of steel flats on floors and walls, along with GFRP sheeting, proved to be an effective solution, reducing stress levels by up to 90%.