Journal of Composites for Construction

Strengthening of RC structures using fiber-reinforced polymer (FRP) systems is a popular rehabilitation technique because of its ease of installation and reduced construction time compared with other methods. Fabric-reinforced cementitious mortar (FRCM) is a new alternative strengthening system with additional advantages including excellent compatibility with concrete substrate and easier postrepair inspection of repaired structures. This paper presents the results of an experimental study on the behavior of shear-critical RC beams strengthened with carbon FRCM (CFRCM) composite systems. Six large-scale shear-critical RC beams were tested. The test variables included the amount of internal transverse reinforcement and CFRCM strengthening. The test results indicated that CFRCM strengthening is effective in enhancing the load-carrying capacity of shear-critical RC beams. However, the effectiveness of CFRCM strengthening decreased with the presence of stirrups and slightly reduced the shear-strength contribution from internal stirrups. The experimental shear-strength contributions were also compared with theoretical predictions using new guidelines from the American Concrete Institute. Finally, the shear transfer mechanism in the CFRCM layer was discussed.

This paper presents test results carried out to investigate the mechanical properties of E-glass fiber-reinforced polymer (E-GFRP) bars with four different diameters (6, 8, 10, and 14 mm) after these bars were subjected to sequential exposure to ultraviolet (UV) radiation and water vapor condensation for different time periods (1,000, 2,000, and 3,000 h) and elevated temperatures (15–300°C). The mechanical properties of the GFRP bars were evaluated with tensile, flexural, short beam (shear), and low-cyclic fatigue tests conducted on 150 specimens after exposure conditions. A scanning electron microscope (SEM) was used to investigate the degradation mechanism of the bars subjected to UV radiation and water vapor condensation. The results showed that, generally, with increases in exposure time and temperature the mechanical properties of the bars decreased. UV radiation and water vapor condensation conditions did not show a significant effect on direct tensile tests, in comparison with flexural and short beam tests. Furthermore, GFRP bars lost up to 45% of their tensile strength at elevated temperatures.

The bond behavior of fiber-reinforced cementitious matrix (FRCM) composites applied as externally bonded reinforcement is the most critical concern in this type of application. FRCM–concrete joints are generally reported to fail because of debonding (slippage) of the fibers from the embedding matrix. However, depending on the characteristics of the composite and substrate used, failure may also occur as a result of detachment of the composite strip at the FRCM–support interface, interlaminar failure (delamination) of the matrix, or tensile failure of the fibers. In this paper, a three-dimensional (3D) numerical model is developed to reproduce the behavior of polyparaphenylene benzo-bisoxazole (PBO) FRCM–concrete joints. The numerical model accounts for the fracture mechanics mixed Mode-I and Mode-II loading condition observed in single-lap direct shear tests by means of nonlinear damaged contact law associated with different interfaces considered in the analysis. The numerical results obtained are compared with those obtained by experimental tests of PBO FRCM–concrete joints. The model is capable of predicting the different failure modes, and it correctly reproduces the experimental load responses including the contribution of friction to the applied stress.