Seismic vulnerability assessment and retrofitting of code non-compliant mixed masonry-RC residential building

Abstract

In seismically active zones like Nepal, it is utmost for the structures to be designed by following proper seismic design criteria. However, the majority of older unreinforced buildings in Nepal are non-engineered or semi-engineered constructions with inadequate seismic detailing. A detailed visual assessment of the Panauti municipality area, led to the identification of a unique building typology which belonged to “non-code compliant mixed Masonry-RC” typology. Finite element (FE) model and pushover analysis was performed for the building, followed by generation of fragility curves and sensitivity analysis. Since the building exhibited vulnerability against the seismic forces, four different retrofitting measures were considered to assess their effectiveness. The result revealed that a combination of full splint and bandage system provides highest strengthening (85% base shear enhancement) and energy absorption capacity (33% greater), while diagonal splint + bandage system provides highest ductility (increment by 174%), whereas splint only retrofit scheme provides highest base shear enhancement per USD (57% per 1000 USD). The research concluded that diagonal splint + bandage is an optimal retrofitting scheme that provide balance on strength, ductility, and economy of the project. The study demonstrated the efficacy of ferrocement bands as a cost-effective strengthening solution for unreinforced masonry buildings in seismically active regions. The findings provide valuable insights for choosing effective retrofitting strategy considering seismicity and economy of the project and the strength, ductility and energy absorption of splint & bandage retrofitting arrangement.