A practical macro-mechanical model for the bend capacity of fibre-reinforced polymer bars

Abstract

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Strength Degradation in Curved Fiber-reinforced Polymer (FRP) Bars Used as Concrete Reinforcement

“…It should be noted that Equations (1) to (4) are empirical and only depend on the geometry of the bend, whilst the bond characteristic between the FRP bar/concrete interface, type of FRP, and material composition are neglected. Recent research by Imjai et al [59] demonstrated that the predictions of Equations (1) to (4) do not match the experimental data available in the existing literature. As a result, Imjai et al proposed a new macromechanical-based equation (Equation (5a)) that more accurately calculates the bend capacity of a bent FRP reinforcement.…”

“…Imjai et al [59] The model adopts the Tsai-Hill failure criterion for a unidirectional orthotropic laminar composite at a macroscopic level and considers force equilibrium at the bent zone. The model is calibrated using test results from 26 tests [33] and subsequently verified against 54 test results available in the literature.…”

“…It should be noted that Equations (1) to (4) are empirical and only depend on the geometry of the bend, whilst the bond characteristic between the FRP bar/concrete interface, type of FRP, and material composition are neglected. Recent research by Imjai et al [59] demonstrated that the The strength degradation at the bent portion of FRP composites is often quantified using Equation (3) (see Table 1), which is included in current design recommendations for concrete structures reinforced with FRP composite materials [34,36,[94][95][96]. It should be noted that Equation 3is based on the JSCE guidelines [45].…”

“…It should be noted that Equations (1) to (4) are empirical and only depend on the geometry of the bend, whilst the bond characteristic between the FRP bar/concrete interface, type of FRP, and material composition are neglected. Recent research by Imjai et al [59] demonstrated that the More recently and based on modifications to Equation (3), Lee et al [48] proposed Equation (4) to calculate the bend capacity of non-circular FRP sections. Non-circular bars are converted into equivalent circular bars using an equivalent diameter with the safety factor (Fs).…”

“…However, equations included in the current design guidelines to predict strength degradation at the bent portion of an FRP bar were empirically derived and are mainly a function of the bend geometry. The results given by such equations do not seem to yield consistent results when different types of composite are used [59]. As a result, there is a need to reassess the accuracy of such equations in light of the existing and new experimental evidence.…”