Experimental and analytical investigation into the flexural performance of RC beams with partially and fully bonded NSM FRP bars/strips

Flexural behavior of RC beams strengthened by NSM GFRP Bars having different end conditions

“…Some of these techniques needed to drill deep holes in the beams to insert the spikes [29], or side planted bolts [30] or steel connectors [1]. Although steel rebar has ribs that bind it mechanically to concrete, it can still pulled out from concrete under high stresses, an occurrence that often accompanies a larger-scale collapse of the structure.…”

“…Although the use of EB technique increases the load carrying capacity of the RC strengthened members, the NSM FRP strengthening technique offers many advantages over EB. These advantages include increasing bond capacity due to larger bonded surface area and make a protection against external damage results from external impacts, since the bar is embedded in the concrete cover [1,2]. Although the researches indicated that the EB and NSM techniques are effective techniques for increasing both flexural and shear capacity of structural members [3][4][5][6], the failure due to debonding of FRP reinforcement is still the most common failure mode [7][8][9][10].…”

“…Several researchers [1,[29][30][31][32] used novel self-anchored fiber-reinforced polymer bars to delay the onset of debonding and to ensure that the NSM FRP reinforcement continues to contribute to member strength after partial debonding. Some of these techniques needed to drill deep holes in the beams to insert the spikes [29], or side planted bolts [30] or steel connectors [1].…”

Load-bearing capacity of flexural reinforced concrete members strengthened with fiber-reinforced polymer in fracture stage

“…The experimental results are collected from different scientific publications. 19,20,[22][23][24][25][26][27] A focus is made on the assessment of crack depth of critical normal section and evaluation of FRP strainstress relationship. The stiffness of strengthened flexural RC members is reduced because of the slippage between concrete and FRP.…”

“…Generally, we can classify FRP systems into two categories: externally bonded reinforcement (EBR), when FRP sheets, plates, or strips are bonded to the surface of the concrete; and near-surfacemounted (NSM), when circular or rectangular FRP bars or strips are installed and bonded in the grooves of the concrete surface. [19][20][21][22][23][24][25][26][27][28][29][30] Seven typical failure modes could be distinguished for RC structures strengthened with FRP: 18 (1) flexural failure caused by FRP rupture, (2) flexural failure caused by crushing of compressive concrete, (3) shear failure, (4) separation of concrete cover of tensile reinforcement, (5) interfacial debonding in FRP plate end, (6) interfacial debonding caused by flexural crack in midspan of the beam, and (7) interfacial debonding caused by intermediate flexural shear crack. Failure mode caused by FRP rupture (mode 1) is appreciated, because, in such case, the full strength of FRP would be used.…”