Shear tests on reinforced concrete beams focused on the transition of beams with and without shear reinforcement

This paper presents an experimental study on the shear resistance of reinforced concrete beams (RC beams) with low or even no shear reinforcement. In contrast to conventional 3-or 4-point bending tests this study includes also tests under different loading and support conditions. A total of 9 RC beams, consisting of 4 single span beams under concentrated loads (4-point bending tests) and 5 cantilever beams under distributed loads will be presented. The shear reinforcement ratio was varied in the range of 0-2.1 times the required minimum shear reinforcement (ρw,min) according to EC2. The different shear reinforcement ratios were realized with closed stirrups of different diameters between 6-12 mm but fixed stirrup spacing. The results show significant differences in the shear resistance between comparable RC beams with different loading and support conditions, especially for beams with low shear reinforcement. Compared to the cantilever beams under distributed loads the increase in shear resistance of the single span beams under concentrated loads was significantly smaller for shear reinforcement ratios around or below ρw,min. However, when the shear reinforcement was increased the test results indicate that the loading and support conditions become less important. The crack pattern was recorded by hand for all beams. A comparison between the test results and the predictions according to some codes of practice e.g., EC2 and MC10, is also provided.