Seismic Strengthening of Reinforced Concrete Columns by Banding Reinforcement of Steel Flat Bar

Abstract

Thailand is prone to higher level of earthquake risk. There is a concern that the columns of reinforced concrete buildings constructed before the enforced regulation of seismic force have insufficient strength to withstand earthquakes or shear failure characteristic that does not dissipate energy well. Therefore, the columns of buildings located in risky areas should be properly strengthening to increase the capacity and ductility. This study proposes a method of banding reinforcement of steel flat bar to increase shear strength and prevent longitudinal buckling of longitudinal rebar. Efficiency determination of strengthening is made by testing reinforced concrete columns with a cross-sectional size of 200x300 mm2 and 1.25 m high under compressive and cyclic lateral loads. Test results show that steel flat bar strapping can change the failure mode from shear failure to flexural failure. The banding is not only increased higher lateral capacity but also significantly improved ductility and energy dissipation. Therefore, the proposed steel flat bar strapping is another option for seismic strengthening of RC columns of buildings that are not earthquake designed in Thailand.