The shear problem in reinforced concrete bending structures

The shear problem for reinforced concrete bending structures is still not solved exactly in spite of large experimental data and many theoretical studies that have been carried out in recent decades. The lack of an exact solution yields high dispersion in predicting concrete shear bearing capacity. There is an additional problem, related to the internal forces carried by shear reinforcement. Generally, the shear problem of bending elements is related to the following two parameters that are known from experiments: the main compression stress angle and that of the inclined links. Corresponding internal forces and the force in the tensile reinforcement form a commonly used truss design model, therefore each force depends on the other (the above mentioned forces form a triangle of forces). This dependence is practically not considered in modern design provisions therefore there is still no exact estimation of shear capacity in bending. If the section of the links is calculated (but not taken corresponding to the minimum value) the two angles should be taken into account simultaneously. The study, described in this paper, is focused on investigating the interaction between the internal forces that appear in concrete due to shear bending and the links following the truss design model. It forms a basis for obtaining the exact angle that defines the direction of inclined cracks and forces in links within known experimental limits.