Quantification of shear cracking in reinforced concrete beams

This paper presents an experimental work and analysis of test results on diagonal cracking behavior of reinforced concrete (RC) beams that failed in shear. The strain distributions of transverse reinforcement, obtained by closely spaced strain gauges mounted inside transverse reinforcement without disturbing bond, are presented in a form of contour lines at different load levels. The diagonal crack width, average principal and shear strain fields of the shear span were obtained by using the digital image correlation (DIC). Based on the strains of transverse reinforcement along the path of the critical diagonal crack, the shear strength contribution of the transverse reinforcement (Vs) is isolated from the shear strength contribution of concrete (Vc). The value of Vs calculated in this way is generally larger than that obtained from the strains measured at mid-height of stirrups in the case of strong bond, while the difference is insignificant in the case of weak bond. With the full and detailed pictures of internal and external strain fields of the beams, important shear characteristics such as inclination of the principal compression strain and its correlation with principal compression stress, variation of Vc and Vs with respect to crack width and member deflection, relationships between crack width, shear force, principal tensile strain of concrete, and strain of transverse reinforcement, etc. are studied in this work. These relationships shed light on further study of the shear behavior of RC beams.