Experimental and Analytical Investigations of the Use of Groove-Epoxy Anchorage System for Shear Strengthening of RC Beams Using CFRP Laminates

Reinforced concrete (RC) beams strengthened in shear with carbon fiber reinforced polymer (CFRP) laminates as externally bonded reinforcement (EBR) usually fail due to debonding. This paper presents an experimental and analytical investigation on the use of groove-epoxy as an anchorage system for CFRP plates and sheets bonded on both sides of shear deficient RC beams. The aim of this study is to assess the effectiveness of using groove-epoxy in enhancing the shear capacity of RC beams. Nine rectangular RC beams were strengthened with CFRP plates and sheets with groove-epoxy anchorage systems of different groove widths and tested under four point bending. It is observed that the RC beams strengthened with the groove-epoxy anchorage system showed an increase in the shear-strength over the unstrengthened control beam up to 112 and 141% for plates and sheets, respectively. Also, the increase of shear-strength contribution of the groove-epoxy system to that of CFRP without grooves ranged between 30–190% for CFRP plates and between 40–100% for CFRP sheets. Generally, the contributions of groove-epoxy on shear-strength decreased with the increase of groove width. Moreover, shear strength prediction models, based on modifications of the ACI440.2R-17 shear model, were developed by incorporating groove factors as a modifier to the FRP shear-strength contribution. The developed models predicted the experimental shear-strength of the tested RC beams with a good level of accuracy, with an average mean absolute percent error (MAPE) = 3.31% and 6.68%, normalized mean square error (NMSE) = 0.072, 0.523, and coefficient of determination R(2) = 0.964, 0.691, for plates and sheets, respectively.