Experimental and numerical study of strengthening non-ductile RC columns with and without lap splice by Carbon Fiber Reinforced Polymer (CFRP) jacketing

This paper presents an effective method for strengthening non-ductile reinforced concrete columns by applying an externally bonded Carbon Fiber Reinforced Polymer (CFRP) fabrics to enhance the shear capacity and confinement. Six rectangular reinforced concrete columns designed for gravity load only were tested under quasi-static cyclic loading. Three columns were provided with short lap-splice length of longitudinal reinforcements at the plastic hinge location to study the effect of lap splice. The experimental results indicate that, by means of CFRP jacketing, the shear strength under reversed cyclic loading is significantly improved as compared to the un-strengthened columns tested in the previous studies. In addition, owing to the confinement from CFRP, the columns exhibit a dramatically improved displacement capability. The nonlinear analysis of columns is also conducted by means of nonlinear fiber section frame element. The key attribute of the nonlinear analysis is to include the effect of lap splice of longitudinal reinforcement through the lap-spring spring model formulated according to the tri-uniform bond stress model. By combining the stress-strain models of concrete, steel reinforcement, lap-splice's bond model, anchorage bond slip and nonlinear shear spring into the fiber section frame element, the numerical results shows a good agreement with experimental ones.