Simulation of Size Effect and Strength Prediction in Normal to Ultra High Strength Concrete Shear Deficient RC Beams

The high rise building construction using normal strength concrete results in larger cross sections, which results in enhanced flexural behavior. Along with the improved flexural behavior, shear characteristics are also increased, which is often overshadowed. Impact of the increasing size on the behavior of reinforced concrete (RC) beams was investigated in this study. The experimental investigation was executed to evaluate the behavior of natural aggregate concrete (NAC), and recycled aggregate concrete (RAC) RC beams under four-point bending. To explicitly study the behavior of RC beams in shear, the beams were kept independent of any shear reinforcement and an shear span to effective depth of 2.68 was kept constant. Numerical simulation was then conducted to replicate the experimental program followed by the investigation of concrete compressive strength and the size effect on the shear behavior of the RC beams. Beams with varying depths of 203 mm, 400 mm, and 600 mm, and widths of 152 mm, 300 mm, and 400 mm, having compressive strength varying from 20 MPa to 150 MPa were investigated. Results were compared in terms of load-displacement relationship and cracking patterns. Furthermore, existing equations for the shear strength prediction of concrete, proposed by different codes, were also studied and compared with the numerical investigations. Based on the investigation, it was observed that the role of size effect in defining the overall shear behavior of RC beams cannot be neglected and the available equations need to be updated to account for size effect.