Flexural Bearing Capacity of Reinforced Concrete Voided Beams: Prediction Model and Numerical Simulation

This study proposes a new capacity prediction model through theoretical derivation and refined nonlinear finite-element analysis to address the insufficient prediction accuracy of the flexural capacity of reinforced concrete voided beams (RCVBs) from existing methods. A modular finite-element model was developed and rigorously validated with experimental data. This model accurately simulated the entire failure process—from initial cracking in the shear key region to concrete crushing—as well as stiffness degradation, demonstrating high precision in the elastic stage (R2>0.960). The distinct failure mechanisms were revealed by the systematic parametric analysis, such as variations in reinforcement ratio. The specimens with moderate reinforcement exhibited ductile flexural failure, with bearing capacity increasing by 30.4%–55.2% compared with the baseline. Over-reinforced specimens underwent brittle shear failure, resulting in a sharp capacity reduction of 62.5%. Moreover, a new prediction model of flexural capacity was derived based on these findings and leveraging the principle of mechanical superposition between concrete and steel reinforcement. This prediction model was validated parametrically, showing high prediction accuracy (R2=0.939) and errors below 10% across different parameter sets. Further parametric analysis indicated that section height was the most significant factor influencing capacity, while concrete strength had a negligible effect. This study provides an accurate and reliable predictive framework for the design and safety assessment of RCVB, offering clear value for engineering applications.