Abstract Despite the enhancement in the flexural capacity of reinforced concrete (RC) members externally strengthened with fiber reinforced polymer (FRP) composites, debonding of the FRP from the concrete substrate at its ends is a major concern. This premature failure mostly occurs at a low fraction of the FRP rupture strain, thus compromises the effectiveness of FRP-strengthening. This paper presents a review on plate-end (PE) debonding as a critical failure mode in FRP-strengthened beams. The available models for predicting this mode of failure are also presented and assessed against experimental database established from previous studies. The precautions recommended by the relevant design codes to prevent PE debonding are also discussed and assessed. Based on the assessment, several conclusions are emphasized, including the inaccuracy in predictions of PE debonding given by most available models when compared with the experimental database and the inconsistency among these models. The assessment also revealed that the precautions recommended by most of the design codes are not adequate to prevent PE debonding.

Reinforced concrete wide shallow beams (WSBs) are commonly used in the joist flooring systems. The structural behavior of WSBs strengthened with carbon fiber reinforced polymer (CFRP) reinforcement was studied on isolated beams and as part of full-scale building. The effect of structural damage on the performance of WSBs flexurally strengthened with CFRP plates was investigated and presented in this paper. Eight full-scale WSBs were tested under four-point bending up to failure. Seven beams were strengthened with CFRP plates bonded to the soffit of the beams and one beam was unstrengthened serving as control. Prior to strengthening, the beams were subjected to different levels of damaging by preloading to 30-95% of the beams' flexural capacity. One beam was fully damaged by preloading to failure and repaired before strengthening by replacing the crushed concrete. The data showed that the pre-damaged strengthened beams exhibited ultimate capacities up to 8% lower than those of the undamaged strengthened beams. However, the load carrying capacities of pre-damaged strengthened beams were more than those predicted by ACI 440 design guide, fib Bulletin 14, and JSCE design recommendations. Both fib Bulletin 14 and JSCE design recommendations gave very conservative predictions with average ratios of experimental to predicted ultimate capacity of 2.02 and 2.35, respectively. More accurate predictions were obtained by ACI 440 design guide as the corresponding ratio was 1.24. These results indicate that strong confidence and reliability can be placed in applying CFRP strengthening to structurally damaged WSBs.

Corrosion of steel reinforcement is one of the major problems that shorten the service life of reinforced concrete (RC) structures. Steel stirrups, due to their location as an outer reinforcement, are more susceptible to corrosion problems and damage. However, there is limited research work in the literature on the effects of stirrup corrosion on the shear strength of RC beams. This paper attempts to evaluate analytically the residual shear strength of RC short beams with corrosion-damaged stirrups. The shear strength of short or deep beams are generally determined using the strut and tie model. The corrosion effects were implemented in the model to make it capable of predicting the residual shear capacity of RC beams with corroded stirrups. The effect of corrosion is implemented considering the reduction in geometry of the concrete cross section due to spalling and reduction in effective compressive strength of concrete due to corrosion cracks. The proposed strut and tie model which accounts for the corrosion effects was verified using the experimental data available in the literature, and good agreement was found.