Evaluating Shear Strength of Reinforced Concrete Elements Containing Macro-Synthetic Fibers and Traditional Steel Reinforcement

This study investigates the shear behavior of concrete elements reinforced with both traditional steel reinforcement and synthetic fibers, with an emphasis on evaluating the predictive capabilities of current shear design provisions. A review of available experimental data revealed limitations in both quantity and consistency, hindering the formulation of robust design recommendations. To address this, an extensive parametric numerical study was conducted using the VecTor2 nonlinear finite element program, incorporating a recently developed modeling approach for the shear response of macro-synthetic fiber-reinforced concrete (PFRC). A total of 288 simulations were carried out to explore the influence of fiber content, transverse reinforcement ratio, and concrete compressive strength, particularly in ranges not previously captured by experimental programs. The performance of existing design codes, including ACI, CSA, EC2, AASHTO, and the Fib Model Code, was assessed against both experimental data and the enriched parametric dataset. The Fib Model Code demonstrated the most reliable and consistent predictions, outperforming others in terms of both accuracy and low variability. In contrast, the EC2 provisions showed high variability and limited applicability to PFRC. AASHTO provisions displayed reasonable accuracy with respect to both experimental and numerical results. ACI and CSA models were notably conservative across the board. The findings underscore the limitations of current code formulations, particularly at high compressive strengths (≥70 MPa) and highlight the need for design models that better account for synthetic fiber–steel bars interaction and material variability. Future work should focus on expanding the experimental database and developing unified design approaches that explicitly address the synergistic effects of fibers and traditional reinforcement.