Finite element modeling of debonding mechanisms in carbon fiber reinforced polymer‐strengthened reinforced concrete continuous beams

Abstract

This paper presents three‐dimensional (3D) and two‐dimensional (2D) finite element models to analyze strengthened reinforced concrete (RC) continuous beams with carbon fiber reinforced polymer (CFRP) which has become familiar technique in the last decade. Experimental results in the literature showed that two different debonding failure modes, either by interfacial debonding of fiber reinforced polymer (FRP) or by concrete cover separation may occur. This study takes the two possible debonding failure modes into account by considering two cohesive surfaces; the first is inserted in the adhesive layer, whereas the second is inserted between the reinforcing steel and the concrete cover. The proposed cohesive surfaces take the slippage into account considering the cohesive surface fracture energy. The numerical models are verified utilizing five symmetrical RC continuous beams available in the literature. The numerical results of 3D and 2D models for the plated beams (beams strengthened with FRP plates) agreed well with the experimental results. Additionally, the effect of the CFRP plate length, and the parameters of the cohesive surfaces on the behavior and debonding failure modes (in the adhesive layer and between the reinforcing steel and the concrete cover) of CFRP‐strengthened RC continuous beams are investigated.

Shear strengthening of reinforced concrete beams using prefabricated ultra‐high performance fiber reinforced concrete plates: Experimental and numerical investigation

“…To the authors' best knowledge most of researchers who studied strengthening of RC beams using UHPFRC material numerically assumed perfect bond between RC beam surface and UHPFRC layers or plates which neglect the slippage between concrete and UHPFRC and cannot capture the debonding failure mode. Herein, the cohesive surface model proposed by Sakr was used to model the adhesive surface behavior, in the following section there is a brief discussion explaining the cohesive surface model.…”

“…A lot more researchers in the last decade studied, experimentally and numerically, the effectiveness of using carbon fiber reinforced polymer (CFRP) as a strengthening material . They concluded that the use of CFRP plates/sheets to strengthen RC beams was effective for reducing deflections and for increasing their load carrying capacity.…”

“…A lot more researchers in the last decade studied, experimentally and numerically, the effectiveness of using carbon fiber reinforced polymer (CFRP) as a strengthening material. [2][3][4][5][6][7] They concluded that the use of CFRP plates/sheets to strengthen RC beams was effective for reducing deflections and for increasing their load carrying capacity. However, they showed that the most common failure mode of CFRP strengthened RC beams is debonding of the composite within a thin layer of concrete.…”

Life cycle reliability assessment of reinforced concrete beams shear‐strengthened with carbon fiber reinforced polymer strips in accordance with fib bulletin 14

“…In many unanchored U‐shaped CFRP beams, the actual failure mechanism is governed by sequential debonding, starting from the most vulnerable strip and continuing by propagation of critical diagonal shear cracking combined with the shear fracture of the beam in other strips . The occurrence of preliminary debonding of the FRP strips does not imply that the beam is not able to survive against existing load effects .…”

“…In many unanchored U-shaped CFRP beams, the actual failure mechanism is governed by sequential debonding, starting from the most vulnerable strip and continuing by propagation of critical diagonal shear cracking combined with the shear fracture of the beam in other strips. 27,54 The occurrence of preliminary debonding of the FRP strips does not imply that the beam is not able to survive against existing load effects. 55 It is important to note that even the occurrence of preliminary debonding may impose a direct adverse effect on the serviceability, durability and subsequently load-carrying capacity of the beam, especially when the strengthened beam is exposed to wetting and drying cycles near seawater (extremely corrosive and Highly degradable, i.e., EH condition) over the longterm operation.…”