Effect of Stirrups on the Shear Failure Mechanism of Deep Beams

The purpose of this study is to clarify the effect of stirrups in deep beams by investigating the shear failure mechanism analytically by using the 3-D Rigid-Body-Spring Model analytical tool. The investigation of the analytical results of the internal stress state and 3-D deformations of deep beams were the key objectives of this study. Firstly, the applicability of the analytical tool on deep beams was confirmed by comparison of analytical and experimental results. Then, the stirrup contribution to load carrying capacity of deep beams was investigated and the shear failure mechanism based on the B and D region concept was clarified analytically. To achieve this, analytical results such as stress distribution, 3-D deformations, crack patterns and strain of stirrups were investigated. Three types of stirrup effect were observed in deep beams. In the a/d= 0.5 case, the peak load increase due to the confinement effect of stirrups. In the a/d=1.0 case, the stirrup contributes to the strut action that leads to an increase in load. In the case of a/d < 1.0, the D region is dominant. On the other hand, the peak load increases significantly with increases of stirrup ratio in the case of a/d > 1.5, in which the truss analogy is dominant rather than the strut action.