Shear Strength of RC Beams with Steel Stirrups

Because of the complexity of the shear failure mechanism, most current design codes and guidelines are based on highly empirical approaches and consequently should only be used within the bounds of testing regimes from which they were derived. Hence this limitation restricts their applicability to innovative materials such as high-strength concrete and fiber-reinforced polymer (FRP) reinforcement. To solve this issue, a mechanics-based segmental approach, which can analyze a reinforced concrete (RC) beam with any type of concrete and reinforcement and which can explain the physical process of shear failure, has been developed to quantify the shear capacity of RC beams without stirrups. In this paper, with the partial interaction analysis of transverse reinforcements directly linked with that of longitudinal reinforcements, the segmental approach is extended by incorporating steel stirrups in the mechanics-based model; furthermore, a simplified closed form solution for design is derived. By evaluating the shear strength of 194 published test specimens, the proposed approaches are validated with good correlation between the predicted and measured strengths. In contrast to current empirical approaches which often assume the stirrups always yield, using the segmental approach it is shown that stirrups' force rarely reaches the value calculated by the truss model. Furthermore, it is shown that direct contribution of the stirrups is less important than the increase in the concrete component of the shear capacity attributable to confinement by the stirrups. Being mechanics based, this approach has a great potential to be developed for all types of RC structures. (C) 2015 American Society of Civil Engineers.