Macro-synthetic fibers are increasingly used in concrete as secondary reinforcement to control temperature and shrinkage cracks, improving durability by limiting crack widths. However, their impact on the shear strength of structural elements remains underexplored, particularly when used in combination with traditional steel reinforcement. To address this knowledge gap, this study developed and calibrated a non-linear numerical model to simulate the shear response of macro-synthetic fiber-reinforced concrete (PFRC) elements, using finite element software VecTor2. The model was calibrated with experimental data from PFRC panels subjected to pure shear loading, incorporating a custom concrete tension-softening model to capture the contribution of fibers. Validation against a broad range of PFRC beam experiments from the literature demonstrated the model’s accuracy, achieving an average predicted-to-experimental shear strength ratio of 0.99 (COV = 5.5%). Additionally, the model successfully replicated key response characteristics such as deformation patterns, crack propagation, and residual strength. The proposed modeling approach provides valuable insights into the interaction between fiber volume and transverse reinforcement. It also serves as a powerful tool for future numerical studies, addressing the existing data gap on PFRC behavior and exploring the synergistic effects of macro-synthetic fibers and steel reinforcement on shear strength.

The combined use of macro-synthetic fibers and traditional steel reinforcement in structural concrete shows promise for enhancing shear behavior, particularly with respect to crack control, ductility, and potentially strength. However, experimental data on such systems remain scarce, especially for elements subjected to pure in-plane shear, where the interaction between fibers and conventional reinforcement is not well understood. This study contributes essential experimental evidence toward addressing this gap. Nine reinforced concrete panels were tested under monotonic in-plane shear, with transverse reinforcement ratios ranging from ρ_v = 0% to 0.91%, and macro-synthetic fiber contents from V_f = 0% to 0.52% by volume. Results showed that fibers were highly effective in reducing crack widths at low reinforcement levels. For specimens with ρ_v = 0.34%, increasing V_f from 0% to 0.52% halved the maximum crack width (from 0.6 mm to 0.3 mm) and reduced the average crack width by 22% (from 0.32 mm to 0.25 mm). Potential ductility improvements were also detected at low reinforcement ratios, with increased shear strain capacities observed as fiber content increased. In contrast, the influence of fibers on shear strength was minimal across all reinforcement levels. These findings highlight the potential of macro-synthetic fibers to enhance the performance of shear-critical elements, particularly in lightly reinforced systems, while also illustrating the need for further experimental and numerical work. The results presented here provide a fundamental dataset that can support future efforts to develop reliable assessment and design approaches accounting for the simultaneous presence of steel reinforcement and synthetic fibers in concrete elements subjected to shear.

This study investigates the shear behavior of concrete elements reinforced with both traditional steel reinforcement and macro-synthetic fibers, with an emphasis on evaluating the predictive capabilities of current shear design provisions. A review of available experimental data, involving 52 beams and 8 panel specimens, 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 PFRC shear response. 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, maintaining close alignment with reference strengths across all fiber contents, reinforcement ratios, and concrete strengths. AASHTO provisions performed moderately well, showing generally conservative and stable predictions, though some underestimation occurred for beams with higher shear reinforcement. In contrast, ACI and CSA models were consistently conservative, especially at higher concrete strengths, potentially leading to uneconomical designs. EC2 models exhibited the highest variability and least reliability, particularly in the presence of fibers, indicating limited applicability without modification. The results highlight that most conventional codes do not fully account for the synergistic action between fibers and transverse steel reinforcement, and that their reliability deteriorates for high-strength PFRC. These findings have practical implications for the design of PFRC elements, suggesting that the Fib Model Code may be the most suitable for current applications, whereas other provisions may require recalibration or modification. Future research should focus on expanding experimental datasets and developing unified design models that explicitly consider fiber–steel interactions, concrete strength, and fiber distribution.

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.