Rotation and moment redistribution capacity of fiber-reinforced concrete beams: Parametric analysis and code compliance

Abstract

Fiber-reinforced concrete (FRC) has been proved to be a competitive solution for structural purposes. Extensive research has highlighted the benefits of adding fibers on the post-cracking strength, reduced crack spacing and crack width, and improved durability, among others. However, these aspects are related to serviceability limit states, and significant work remains to be done in terms of ultimate limit state behavior of FRC members. As recent publications have emphasized, reinforced concrete beams with low reinforcement ratios may result in a reduction of deformation capacity and, hence, to a loss of ductility. To further investigate this topic, this paper presents the results of a numerical parametric study of simply and continuous supported hybrid-reinforced concrete (HRC) beams made with different amounts of fibers and reinforcement ratios. The deformation, rotational, and moment redistribution capacity of those were assessed by means of a finite-element model previously calibrated using experimental results available in the literature. The results showed that there is a significant reduction of rotation capacity and moment redistribution for lightly reinforced (hybrid) members. Finally, the paper contains practical recommendations in terms of minimum reinforcement ratios that guarantee adequate rotation and redistribution capacity of HRC members. As such, the results of this study can provide a contribution toward more reliable structural designs of HRC members.