Effects of Grouting Defects in a Duct on the Bonding of Prestressing Strands

Abstract

Insufficient grouting has a great effect on the bonding performance of pressing stand for a post-tensioned prestressed concrete beam, which leads to a decrease of beam’s bending capacity. This study focused on the influence of defects of local grouting length and grouting fullness on the prestressing strand’s bond performance. The prestressing strand pull-out test was used to evaluate the bonding performance of pressing stand with different defects of local grouting length and grouting fullness. The results indicate that two forms of grouting defects reduce the bonding properties of a prestressing strand, when the slip of the free end of prestressing strand is 0.12 mm (s = 0.12 mm), the bond stress decreases briefly. To analyze the bonding mechanism of the prepressing strand in duct, the bond stresses τ0 and τu at s = 0.12 mm and s = 25 mm were adopted as the characteristic parameters of bond stress to deduce the calculation formula of the bond strength by fitting the test data. A bond-slip constitutive model of prestressing strand in duct under two classes defects was proposed by improving the modified Eligehausen, Popov and Bertero (BPE) model of fiber reinforced polymer (FRP) rebars.