SUMMARY
One of the best ways of achieving sustainability is to prolong the life span of existing structures instead of the “demolish and rebuild” option. Structure rehabilitation reduces construction waste, conserves natural resources, reduces negative environmental consequences, saves time, and saves cost, etc. Two main categories can be noticed in rehabilitation: repairing and strengthening. This study will focus on the strengthening category. The seismic analysis of existing reinforced concrete buildings before and after strengthening their columns is considered in this study. Three strengthening techniques (Ferro-cement jacket, steel jacket and Carbon fiber reinforced polymer jacket) are used to strengthen the reinforced concrete columns. The building is considered to be subjected to El Centro earthquake in two horizontal directions. The main objective is to investigate the optimum number and locations of the columns required to be strengthened so that the strengthened building satisfies the performance level. Four states of the building are considered; the original building and three strengthened buildings. The strengthening of a part of column height (only one meter along the potential plastic hinge) is considered. The results show that all three strengthening techniques are efficient to resist the seismic loads. This study helps engineers to select suitable, feasible and efficient strengthening techniques for structural members in existing buildings.