Numerical analysis of prestressing strand placement impact on dapped-end beam bearing capacity

Abstract

Dapped-end beams, prevalent in structural design for their distinct advantages, pose unique challenges when integrating prestressed reinforcement. The geometric discontinuities in these beams result in complex stress patterns that are not accurately accounted for by conventional design calculations. Moreover, the effect of prestressing on these beams’ bearing capacity, particularly in specific configurations, is not thoroughly understood. This research uses a numerical parametric analysis to scrutinize the influence of prestressed strand placement in the dapped end and the intensity of prestressing. The severity of the decrease in bearing capacity was found to be dependent on the distance of the prestressing strands from the bottom face of the beam, with larger distances resulting in a less severe impact. In cases of beams without longitudinal and shear reinforcement, the effect was notably substantial, leading to reductions ranging from a significant 40.1% to a minimal 2.2%. For fully reinforced beams, the influence of the strand distance was less pronounced, leading to reductions between 22.9% and 18.8%. The study revealed a direct correlation between the intensity of the prestressing force and the reduction in bearing capacity. In every instance examined, an escalation in prestressing intensity corresponded to a more noticeable decrease in bearing capacity. For reinforced beams, a decrease of up to 22.9% was observed when the σcp/fcm ratio approximated 0.25. The research emphasizes the importance of considering this impact during the design process of such beams.