This paper presents the current code provisions on strut-and-tie analysis and design of disturbed regions of deep concrete beams reinforced with fiber-reinforced polymer reinforcing (FRP) bars. A literature review of the large-scale experiments published to date is included with a comparison of their results to strut-and-tie predictions. Several published works have recommended modifications to strut-and-tie provisions for FRP reinforced deep beams, and those modifications are summarized within this paper.

The study delves into modeling the interface between Fiber-Reinforced Polymer (FRP) and concrete, with a specific emphasis on simulating the gradual deterioration of bond strength. A model rooted in continuum damage mechanics is integrated with an empirically derived relationship to address interfacial shear failure. Material models are defined for the concrete, the externally bonded FRP reinforcement, and the adhesive layer. These material models are implemented in finite element simulations, replicating experimental setups widely used to investigate the FRP-concrete interface. Key results are reported and discussed. More precisely, the numerically obtained load-slip relationships for the interface and visualizations of the damaged zones in concrete are provided. The numerical results are in close agreement with existing experimental data. The finite element analyses suggest that concrete degradation is not limited to the areas near the adhesive joint. This implies that the adhesive joint could influence the overall behavior of the structural elements, even when debonding failures are prevented by anchorage devices.

This paper presents a new methodology for characterizing the failure mode of structural walls reinforced with glass fiber reinforced polymer (GFRP) bars. An analytical model is used to derive a non-dimensional failure determinant function, which is validated against existing test results. The function involves geometric attributes (wall length, wall height, and boundary element size), reinforcement ratios (horizontal and vertical), and material properties (compressive strength of concrete and tensile strength of GFRP bars). According to the determinant function, structural walls fail in flexure when a high aspect ratio is associated with a relatively low reinforcement ratio in the boundary element. The proposed methodology and design recommendations provide valuable guidance for practitioners dealing with GFRP-reinforced concrete walls.

This paper presents an indeterminate strut-and-tie (IST) method to analyze concrete deep members reinforced with fibre-reinforced polymer (FRP) bars. Because FRP bars are linear-elastic and brittle at failure, the classical ST method based on steel yielding cannot be used to analyze FRP-reinforced concrete deep beams, and current code provisions lack guidance on such designs. Thus, the IST method is proposed for the analysis. This work addresses the details of using the proposed IST method to analyze FRP-reinforced concrete deep beams, including how to size the struts and nodes without assuming steel yielding, how to model the compressive behaviour of concrete struts reasonably, and how to construct and analyze statically indeterminate ST models. Six FRP-reinforced concrete deep beams with stirrups and six beams without stirrups are analyzed in this work, and it is found that the proposed method works well to predict the shear strength of FRP-reinforced concrete deep beams by comparing the analytical results with the test results.

This study evaluates the bond performance of concrete epoxy bonds using an image segmentation-based image processing technique. The Concrete Epoxy Interface (CEI) plays a crucial role in the structural performance of FRP-repaired concrete as it transfers stresses from the concrete to the epoxy. By employing the image segmentation technique, the performance of the CEI is assessed through the ratio of Interfacial Failure (IF) to other failure types, namely cohesive failure in Epoxy (CE) and Cohesive cracks in Concrete (CC). The effects of sustained loading duration on CEI bond performance are quantitatively analyzed using 21 single-lap shear (SLS) specimens and 28 notched 3-Point Bending (3PB) specimens. The findings highlight vital conclusions: CE is the least failure mode in SLS and 3PB specimens. In contrast, CC is the predominant failure mode, indicating the susceptibility of the concrete substrate in FRP-repaired concrete. Moreover, IF generally increases with longer sustained loading durations in 3PB specimens but decreases with increased loading duration in SLS specimens. The study also demonstrates the effectiveness of the image segmentation approach in evaluating CEI performance in 3PB specimens, where color distinguishes epoxy, FRP, and concrete substrate.