Optimal seismic retrofit method for reinforced concrete columns with wing walls

Seismic retrofit of reinforced concrete (RC) columns using wing walls can be used to improve the shear and flexural strength of the column through a relatively simple process. However, the feasibility and efficiency of the seismic retrofitting of RC frames with wing walls heavily depends on the selection of number of columns to be retrofitted, the cross-sectional dimensions of wing walls, and the quantity of re-bars of the wing wall. In this study, an optimal seismic retrofit design method is proposed to minimize not only the initial retrofit cost but also the earthquake-induced damage expected during the life cycle of the building. The seismic performance of structures before and after the application of the retrofit has been verified with the comparison of four response parameters: pushover curves, the inter-storey drift ratios, the energy dissipation capacities, and failure modes. The proposed retrofit method is applied to seismic retrofit of a six-storey RC building example and an actual RC building structure in use. For the retrofit of actual building structure, with an initial retrofit weight of 70.85 kN, which corresponds to 1.85% of the weight of the non-retrofitted building, the energy dissipation capacity was increase by 3.02 times and the life cycle cost (LCC) of the retrofit was reduced to 69.47% of the required LCC for the non-retrofitted building. In addition, it has been confirmed that no storey collapse occurred in collapse prevention level, which indicates the most severe failure mechanism of a structure due to an earthquake.