Assessment of Debonding Load for RC Beam Strengthened with Pre-designed CFRP Strip Mechanism

Abstract

With passage of time, strengthening techniques have become more and more refined. Carbon fiber reinforced polymer (CFRP) and steel plates have been adopted since years as few of the popular materials for strengthening of structural elements such as beams and columns. A series of studies have been carried out in the past for shear strengthening of reinforced concrete beams using various mechanisms of strengthening, and response of such strengthened structural elements is found to be quite satisfactory as compared to non-strengthened structural elements. De-lamination/debonding is a major issue faced while strengthening any structural member using fiber reinforced polymer (FRP). Debonding occurs at regions of high stress concentration, which are often associated with material discontinuities and with presence of cracks. However, this can be avoided, if strengthening is done after proper understanding and analysis of the problem. Adaptation of proper guideline to overcome debonding plays a vital role in the resolution of debonding problem, however these guidelines are also limited. The increasing use of FRP in structural strengthening although has revoked a need for framing of guidelines in this segment, but eventually fails to address the debonding aspect to a larger extent. Also, the debonding load after strengthening remains unknown. The magnitude of this load, if known, can contribute to a much greater extent as long as FRP strengthening is concerned. This paper aims at highlighting the method for strengthening of reinforced concrete beam in flexure and shear using CFRP strip mechanism and thereby overcoming CFRP debonding problem in order to achieve enhanced performance in flexure and shear along with prevention of strengthened member failure against debonding.