Influence of Flexural Reinforcement on Shear Strength of Prestressed Concrete Beams

To investigate the shear strength and behavior of partially prestressed reinforced concrete beams, nine large-scale rectangular beams reinforced with both prestressing strands and reinforcing bars without transverse reinforcement were tested. The test program consisted of three series. Each series of specimens consisted of three beams; one beam included only prestressing strands, whereas the other two beams had varying amounts of reinforcing bars. In all nine specimens, the prestressing force was maintained constant. The primary test variables included the amount of prestressing steel and the amount of mild steel. The specimens were simply supported and loaded with a concentrated force at midspan. All specimens had a shear span-depth ratio of 3.33. The behavior of the specimens is discussed, and the test results are compared to evaluate the influence of the mild reinforcement, the amount of prestressing reinforcement, and the total amount of flexural reinforcement provided. Further analyses were conducted to consider the influence of the neutral axis on shear strength. This investigation demonstrates the importance of flexural reinforcement (prestressed and mild) on the shear strength of prestressed concrete sections. In addition, it demonstrates a strong correlation between the neutral axis depth and the shear strength provided by the concrete.