Significance of Stress-Block Parameters on the Moment Capacity of Sections Under-Reinforced with FRP

Abstract

Synopsis: For under-reinforced concrete sections reinforced with FRP, failure of a member is initiated by rupture of the FRP bar and the typical ACI compression stressblock might not be applicable. This is because of the fact that the corresponding strain at the extreme fiber of the concrete will not reach the ultimate strain in concrete. Therefore, accurate computation of flexural capacity requires developing equivalent stress-block parameters that represent the stress distribution in the concrete at a particular strain level. While the ACI 440 permits the use of a simplified approach to calculate moment capacities that do not require equivalent stress-block calculations, the significance of this simplification needs to be examined. This paper suggests a family of curves based on the extreme fiber strain in concrete using three existing stress-strain models. The paper highlights the significance of these curves for different values of compressive strengths of concrete.