Developed method for analyzing maximum shear capacity of RC beams retrofitted with embedded through-section FRP reinforcement

This study presents a method for predicting the maximum shear capacity of reinforced concrete (RC) beams strengthened with embedded through-section (ETS) fiber-reinforced polymer (FRP) bars, drawing upon established theory for conventional RC beams. By considering the three main failure mechanisms-shear tension, compression, and flexure-governing the behavior and failure of shear-subjected beams, the study identifies the permissible maximum capacity. The developed method integrates a bonding-based approach to analyze the shear resistance of the ETS-FRP strengthening system, accounting for its bonding to concrete. Moreover, the model incorporates the participation of the beam flange, enhancing its accuracy in capturing beam behavior. Strain compatibility, linking the shear behaviors between concrete, steel stirrups, and ETS-FRP bars, is embedded into the method. Validation against experimental data from the literature demonstrates the model's superior accuracy compared to guideline equations. The average ratios of calculated to experimental beam shear strengths (Vtotal_Cal./Vtotal_Exp.) are close to 1.0, with coefficients of variation (CoV) less than 0.20. In contrast, the mean ratios and CoV from the models provided by the American Concrete Institute and Japan Society of Civil Engineers are no greater than 0.6 and no less than 0.25. Furthermore, the developed model enables reasonable analysis of beam failure modes. The study also highlights the influence of flange size on shear capacity, with larger flanges resulting in higher capacities, and recommends the effective flange width for practical design. Overall, the inclusion of strain compatibility facilitates a comprehensive design approach for ETS-FRP-strengthened beams.