Design Approach for Flexural Capacity of Prestressed Concrete Beams with External Tendons

Abstract

Due to a lack of bonds between external tendons and adjacent concrete and the potential variation in the eccentricities of the tendons (second-order effect), the analysis of the ultimate strength behavior of externally prestressed concrete (PC) beams is rather complicated. In this paper, a new design approach is proposed to calculate the flexural capacity of simply supported PC beams with external steel or fiber-reinforced polymer (FRP) tendons. First, an assumed deflected shape of a beam, which is supported by a comparison of experimental and analytical results, is incorporated into a beam–tendon structural deformation model to implement global deformation compatibility. In conjunction with sectional equilibrium and compatibility, simplified yet rational design equations are then developed to predict the ultimate stress increase in external tendons. Finally, a design approach that takes into account the second-order effect is proposed to calculate the flexural capacity of the beams. It is found, by comparing their predictions with available experimental results on 96 beams, that the proposed approach is more consistent and accurate than existing guidelines or models.