Influence of axial compression on the shear capacity of RC beams without stirrups

This contribution presents an experimental program of 18 reinforced concrete (RC) beams without stirrups subjected to shear under compression. The loading conditions consist of a three-point bending loading with a shear force (applied by a vertical hydraulic jack) on the one hand, an axial compression and a negative bending moment applied at each end of the beams (by two horizontal hydraulic jacks with an eccentricity of 0.4 m with respect to the beams' mid-height) on the other hand. Three values of axial compressive force are studied. The test beams are divided into two series with and without negative bending moments, respectively. During the tests, Digital Image Correlation technique is used to capture cracking evolution of the specimens. Results of these tests may provide a useful experimental data base to validate models for the prediction of the shear failure behaviour. Analysis of experimental results makes it possible to identify, not only the influence of compressive force but also the effects of bending moment, on the shear capacity of RC beams. Comparison of the experimental shear resistances with those predicted by Eurocode 2 shows that such a design code may be unconservative in overestimating the beneficial effects of axial compression, but ignores significant favourable effects of negative bending moment, on the shear strength of RC beam elements.