Flexural strengthening of reinforced concrete beams using hybrid near-surface embedded/externally bonded fabric-reinforced cementitious matrix

Abstract

The efficacy of hybrid near-surface embedded/externally bonded (NSE/EB) fabric-reinforced cementitious matrix (FRCM) for flexural strengthening of reinforced concrete (RC) beams was assessed experimentally. Bending tests were conducted on eight RC beams: 6 strengthened and two reference beams. The test parameters were (a) the internal tensile reinforcement ratio and (b) the FRCM fabric type (glass, polyparaphenylene benzobisoxazole (PBO), and carbon). The experimental results revealed that the hybrid NSE/EB-FRCM could effectively be used for the flexural strengthening of RC beams based on the test parameters. The strengthened beams exhibited an enhanced flexural behavior as evidenced by their increased load-carrying capacity (Pu) that ranged between 24.7% and 109%. The maximum enhancement in the load-carrying capacity was measured in carbon FRCM strengthened beams owing to the higher axial stiffness of carbon FRCM relative to PBO and glass FRCM. The strengthening efficacy of the FRCM was increased with an increase in the FRCM axial stiffness. An increase in the internal tensile reinforcement ratio showed an adverse effect on the gain in Pu. The stiffness factor (βf) was used to study the combined effect of the test parameters. An almost linear relationship was observed between the increase in Pu and βf with a good coefficient of correlation of 97%. Moreover, the strengthening system has increased the post-crack stiffness of the beam with an average increase of 52%. Finally, the prediction of the ACI 549 provisions was examined and compared with the experimental results.