Influence of the plastic hinge rotations on shear strength in continuous reinforced concrete beams with shear reinforcement

Abstract

Continuous reinforced concrete (RC) beams may develop significant plastic rotations to enable the redistribution of bending moments. These rotations occur at plastic hinges, which are subject to high shear forces. The influence of rotations on the shear strength for statically determined beams without shear reinforcement failing in shear after yielding of the flexural reinforcement has already been experimentally verified. However, this influence has not been studied in continuous members with shear reinforcement. An innovative tests system has been specially designed to develop shear failures before and after yielding of the flexural reinforcement in both statically determinate and indeterminate structures.Nine beams (9000 mm long, 250 mm wide, 450 mm high) with a shear reinforcement of ϕ8/30 (ρw = 0.13%) and different longitudinal reinforcement ratios were tested under different load and support conditions.The shear strength provided by shear reinforcement and that provided by the other mechanisms of resistance (shear strength provided by concrete) for each specimen were calculated based on the critical shear crack width measurements performed by Digital Image Correlation (DIC). Bending rotation and crack rotation along the development length of the critical shear crack were also obtained by DIC.Based on the test results, the shear strength provided by concrete was studied in relation to the bending rotation and the average crack width in reinforced concrete beams with shear reinforcement. It was confirmed that the shear strength provided by concrete decreased with increasing both bending rotations and crack widths. The shear strength values predicted by different design codes (ACI 318-19, Eurocode 2 and Model Code 2010) were compared with the test results, and showed that these formulations did not properly capture the loss of shear strength caused by bending rotation.