Analytical Model for RC Beams with Externally Bonded Laminates Using Strut-and-Tie Method

Abstract

An analytical model for RC beam strengthened with externally bonded laminates based on the strut-and-tie method is reported herein for predicting the strength and mode of failure of the strengthened RC beam. From the proposed model, four inequality equations were derived corresponding to four possible modes of failure. These four inequality equations define a safe domain. When the loading path up to the ultimate flexural limit state of a beam is plotted on the same diagram, the mode of failure and strength of the beam can be identified. The possible modes of failure consist of both flexure-type and shear-type failures. Flexure-type failure is due to the yielding of internal longitudinal reinforcement or the yielding of externally bonded laminates, whereas shear-type failure is due to the crushing of the diagonal compressive concrete strut or the yielding of the shear reinforcement. The failure mode initiated by one flexure-type followed by another is possible. Mode of failure initiated by one flexure-type followed by a shear-type is also possible but not otherwise. In short, this model describes the mode of failure and the corresponding strength of an RC beam strengthened with externally bonded laminates, which can be used to verify the adequacy of design for beam strengthening.