Nonlinear High-Order Analysis of Cracked RC Beams Strengthened with FRP Strips

Abstract

A nonlinear analysis, based on the closed-form high-order approach, for the behavior of cracked reinforced concrete beams, retrofitted with externally bonded fiber-reinforced plastic (FRP) strips, is presented. The model is based on equilibrium, compatibility of deformations, and the nonlinear constitutive relations of the various materials. The nonlinear implicit governing equations are derived and are solved through an iterative linearized procedure. Verification of the nonlinear model is achieved through comparison of the load-deflection response with the experimental result. The results of the proposed analysis include global effects such as load-deflection response and the development of the tensile stresses in the FRP strip and localized effects such as the shear and peeling stresses near the edge of the strip. The study reveals that the extreme values of the stresses at the edge region and the in-plane stress resultant in the strip exhibits nonlinear dependence on the imposed load, which the linear approach is incapable of predicting. Thus, the use of linear analysis for cracked concrete beams underestimates the stresses in the FRP strip and in the adhesive layer. Prestressing of the FRP strip is investigated, revealing that the strip must be properly anchored to exploit its advantages. This paper ends with a summary and conclusions.