Seismic retrofitting of masonry infilled RC buildings in low-to moderate-seismic regions: case study of typical Sri Lankan school buildings

Seismic retrofitting solutions for reinforced concrete (RC) school building types in high-seismic regions are extensively reported in the state-of-the-art. Conversely, limited studies have focused on the extent of retrofitting needed for RC school buildings in low- to moderate-seismic regions. To explore this aspect, seismic retrofitting options for RC school buildings in Sri Lanka are investigated. Three retrofitting options are examined: (1) adding/altering masonry infill walls (MI walls) to reduce irregularity in buildings, (2) RC jacketing of columns and (3) a combination of adding/altering MI walls and RC jacketing. These retrofit options are applied to a common typology of Sri Lankan MI-RC school buildings, considering two and three storey height variations. A simplified numerical modelling approach that accounts for the contribution of MIs, the shear failure of RC column and torsional effects is adopted to analyse the performance of the school buildings with and without retrofit. Based on the analyses, three damage states are defined: damage limitation (DL), significant damage (SD) and near collapse (NC). Finally, a multi-criteria decision making (MCDM) method is used to determine the optimal retrofitting option for the considered school building typology, considering engineering and economic parameters. The optimal retrofit solution for the three-storey MI-RC school building is found to be jacketing of ground floor columns. Conversely, for the two-storey MI-RC school building, alteration of infill walls (MI walls) is deemed optimal. Finally, a sensitivity analysis is carried out on the MCDM method.