Improving the flexural behavior of RC beams strengthening by near-surface mounting

This article presents the experimental investigations undertaken to evaluate the strengthening and enhancement characteristics of near-surface mounted (NSM) devices using different types of bars. A total of 4 concrete beams (150 mm x 300 mm x 1,500 mm) were reinforced in flexure. Three beams strengthened with different embedments of NSM (carbon fiber-reinforced polymer [CFRP], Glass fiber-reinforced polymer [GFRP], and steel) bars, and one unstrengthened beam used as a control beam were tested under monotonic static loading to determine the enhancing influence of the fiber-reinforced polymer (FRP) reinforcement. The performance of different bars used to establish the concrete is examined. A general methodology to evaluate the improving flexural behavior of RC beams strengthened with NSM-FRP bars is presented. A quantitative criterion governing debonding failure is established. The proposed bond model assumes linear elastic behavior for the concrete, adhesive, and NSM-FRP bars, following the same philosophy as the American concrete institute [ACI] provisions for bond analysis and design to control the cracks. So FRP reinforcements show substantial deformation before failure when the cross-sectional area is based on a permissible strain during service, so there is no need to check the deformability. The results of the tests show that using NSM-CFRP bars improves the flexural capacity and stiffness of the strengthened concrete beams of other types.