Mechanism of tensile load sharing in hybrid reinforced concrete flexural members

Abstract

This paper investigates the flexural behavior of Hybrid Reinforced Concrete (HRC), a composite material combining conventional rebars and short, randomly distributed fibers. The synergy between these components enhances serviceability stiffness, deflection control, ultimate strength, and load-sharing efficiency. Flexural experiments were conducted on nine HRC beams with varying proportions of flexural, skin, and fiber reinforcement. A closed-form analytical model was used to predict the moment-curvature and load-deflection responses, showing good agreement with experimental data for sectional strain, neutral axis depth, and deflection throughout the loading history. Results demonstrate that fiber significantly improves structural performance by delaying crack instability and increasing post-cracking stiffness. Replacing 50–80 % of longitudinal reinforcement with a 1.25 % volume fraction of steel fibers increased the serviceability moment capacity by 43–65 %. The fiber bridging mechanism was found to carry a substantial portion of the tensile load (74–92 %) in the cracked concrete matrix within the serviceability range, leading to higher stiffness retention. However, reducing the longitudinal reinforcement by as much as 80 % and replacing it with up to 1.25 % fibers decreased the ultimate load by 10–50 %.