EVALUATION AND RETROFITTING OF EXISTING RC BUILDING

Abstract

Retrofitting of buildings has become vital to strengthen structures that have outlived their design life or for buildings whose structural capacity has considerably deteriorated during natural calamities. Deficient buildings are highly vulnerable to seismic events, resulting in fatalities and massive economic losses. The non-engineered buildings and buildings with irregularities like soft storey buildings in high seismic zones pose an enormous threat to the people living in those buildings. This study considers a deficient building from Dimapur in Nagaland, located at the Indian seismic zone-V. A significant percentage of the medium and low-rise buildings in this region are constructed to withstand gravity loads, not much emphasis has been given to resisting seismic loads. Local retrofitting techniques such as GFRP wrapping, CFRP wrapping and Concrete Jacketing have been implemented on the columns of the model, nonlinear static and dynamic analysis was performed for the models, and performance comparisons of all the building models have been made. The study also focuses on the behaviour of Open Ground Storey (OGS) buildings where the soft storey mechanism is experienced. These buildings are mainly constructed to provide open parking spaces at the ground story level in densely populated urban areas; however, past earthquakes have shown these buildings as extremely vulnerable. After the 2001 Bhuj earthquake, improvements were made to the existing Indian seismic design code, and design provisions for soft storey structures were formulated in IS:1893-1 (2002) and updated in 2016. The behaviour of OGS buildings during seismic events and their performance after implementing the global retrofit technique by adding concentric steel braces on the ground storey frames have been studied, study was also carried out for the buildings designed with a multiplication factor of 2.5 as per Indian Standards. The findings from the study discourage the construction practice of OGS buildings in reigons of high seismic zones.