INVESTIGATION OF SPECIFIC RETROFITTING TECHNIQUES FOR MASONRY SCHOOL BUILDINGS IN NEPAL

Abstract

The 7.8 Mw earthquake that occurred on April 25, 2015 caused a significant damage on the most of the school buildings. The earthquake and its aftershocks had a significant negative impact on the education system of Nepal. Vast majority of damaged school buildings were unreinforced masonry. Many of them were partially damaged. Such buildings are deficient in seismic load carrying capacity. Due to this, retrofitting is necessary to upgrade its capacity. Splint and bandage and Reinforced concrete jacketing are two popular methods of retrofitting used for school buildings in Nepal. However, their appropriateness in the building type is still under discussion. This study aims to investigate these retrofitting technique to discuss its suitability for masonry school buildings. Five types of school buildings with different aspect ratio and storey were selected for this study. The masonry school buildings are analyzed for before and after retrofitting condition. Splint bandage and reinforced concrete jacketing was used for retrofitting masonry school buildings. Only brick masonry with cement mortar school buildings were studied. Linear analysis was performed in SAP2000 and nonlinear analysis was performed in DIANA FEA for all five type of buildings. Shell elements were used in SAP2000 and solid elements were using in DIANA FEA. This study showed that the stresses in masonry can be reduced by providing reinforced concrete jacketing at critical location. Due to this, drastic increase in the capacity of masonry buildings is observed. The ultimate load carrying capacity is increased by as high as 764.03% in some buildings. Ductility is also increased by 4.16% to 86.77% of the original building. Tentative cost analysis of superstructure of one of the building also shows that the cost is around 30% of reconstruction cost and hence economically viable. These enhancements in performance and economic viability show that these retrofitting techniques can be applied for masonry school buildings.