| Abstract | Reinforced Concrete buildings are commonly built in urban areas. Due to rapid increase of population, lack of availability of land and urbanization, construction of mid-rise RC buildings is increasing in number. These buildings have brick infill walls as partition walls and exterior walls. These are considered as non-structural component and their effect is neglected during the process of designing. But, infill walls can increase the initial stiffness, strength to the structure which can alter dynamic behavior of the building. On the other hand, irregular distribution of these walls can cause torsional effect and soft storey effect in the building. The buildings can be vulnerable to earthquake due to the presence of infill walls. A mid-rise building having irregular distribution of infill walls is selected from seismically active zone in Nepal. Nonlinear modelling of the building is done in PERFORM-3D and subjected to various ground motions representing different earthquakes. Seismic performance of the building is done in terms of displacement, drift, base shear, overturning moment, plastic rotation and axial strain. The building showed an unacceptable performance for severe earthquake ground motions. Hence, in order to improve the seismic performance of the building, different retrofitting methods were used. Firstly, complete infill walls were added to improve the irregularity in plan and in turn eliminate torsional behavior of the building. The performance of the building is improved but, it is still in unacceptable level. Secondly, shear walls were added in the building maintaining symmetry as new method of retrofit. The performance of building is improved globally as well as locally, and the performance is under acceptable limit. But, new foundation has to be built and the dead weight of building will increase significantly on addition of shear walls. Hence, Buckling Restrained Braces were added as new method of retrofit. BRBs helped in achieving desired performance objective. Among three methods, BRBs serve as the most effective solution for seismic retrofitting of the building.
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