An investigation on shear strength of reinforced concrete columns strengthened by concrete jacketing

Abstract

The existing reinforced concrete buildings may need to be strengthened to reduce damages during upcoming earthquakes. The study reported in this paper is on strengthening of columns which are deficient in resisting shear during an earthquake, adopting concrete jacketing technique. Based on the previous studies, a need to develop a method to predict shear strength of jacketed columns, and to study the parameters affecting the strength was identified. To fulfil these objectives, experimental and analytical studies were conducted on shear-critical concrete jacketed specimens. Thirty eight beam-column specimens were designed, prepared and tested, based on the selected parameters affecting shear strength. The parameters considered were, compressive strength of jacket concrete, amounts of longitudinal and transverse reinforcement of jacket, thickness of jacket and level of axial compression. All the specimens were designed to fail in shear. A method to compute the shear strength of a jacketed member, by extending the equations available for a monolithic section in selected standards is demonstrated. The method was validated using the test results. Next, the effects of the variations of the parameters on shear strengths of the jacketed members are illustrated. Finally, an overview on the improvement in strength and behaviour due to jacketing is presented.