Prediction of the post-peak behavior of reinforced concrete columns with and without FRP-jacketing

A new method to predict load–deformation envelope responses of reinforced concrete (RC) columns both with and without fiber reinforced polymer (FRP) jacketing under seismic loading is presented. This flexure–shear interaction (FSI) analytical method for both strength and deformation includes (i) a shear strength model representing degradation of shear strength in post-peak region, (ii) a shear deformation model in the plastic hinge zone in the post-peak region, (iii) a flexural strength model considering confinement effects of transverse reinforcement and jacket, and (iv) a flexural deformation model. The interactions include (i) neutral axis depth reduction due to shear cracking, (ii) flexural reinforcement stress increase due to shear cracking (tension shift effect), (iii) effects of yielding of flexural reinforcement on shear strength, and (iv) effect of concrete compression softening on shear strength. The proposed analytical approach is verified by means of a series of experiments on square columns strengthened with and without FRP-jacketing tested under reversed cyclic loading; parameters such as steel reinforcement and fiber ratio were varied. The proposed analytical method is demonstrated to predict accurately the pre-peak and post-peak load–deformation response, including the strain response of shear reinforcement until the ultimate point of the rupture of non- and FRP-jacketed RC columns, and can be concluded that fibers with high fracture strain can provide good ultimate ductility.