Flexural Strengthening of Reinforced Concrete Beams by Different FRP Products Using Near-Surface Mounted Technique

Abstract An experimental study was performed on reinforced concrete (RC) beams enhanced in flexural capacity using the Near Surface Mounted Fiber Reinforced Polymers (NSM-FRPs) method. This study evaluated the efficacy of various FRP application processes and provided quantitative data on the bonding behavior between FRP and concrete. Effects of FRP type and shape, with equivalent area, on load-bearing capacity, midspan deflection, and failure mode of RC rectangular beams were tested under simply supported conditions with two-point loading up to failure. Beam dimensions are 150 mm × 200 mm × 1700 mm with flexural reinforcement (2ϕ10 at top and 3ϕ12 at bottom) and shear reinforcement (ϕ8@70 mm stirrups). Variables expected to affect strengthening system efficacy are discussed, specifically the type of fibers (carbon, glass, and basalt) and shape of elements (sheet, bar). Using different fiber types is an efficient method to enhance flexural strength of RC beams; capacity increased by 19.6% for NSM-FRP sheets and up to 107.6% for NSM-FRP bars. Strengthening with basalt, glass, and carbon NSM-FRP bars increased ultimate load by approximately 92.9%, 75.6%, and 107.6%, respectively, compared with the control beam. In contrast, NSM basalt, glass, and carbon sheets showed lower increases in ultimate load (about 11%, 16.3%, and 19.6%), respectively.