Modelling the degradation of externally bonded post-tensioning tendons including bond-slip behaviour

Abstract

In recent years, brittle fractures of externally bonded post-tensioning tendons have been observed in bridges worldwide, compromising structural safety and durability. Consequently, concern has increased about the mechanical behaviour of these elements when strand or wire breakages occur due to corrosion. This paper presents a finite element modelling strategy for bonded tendons incorporating a non-linear bond-slip law at the strand–grout interface, enabling a detailed representation of tendon behaviour. The objective is to investigate the influence of the bond-slip law on tendon degradation. Two experimental case studies, where progressive damage is induced, have been modelled considering different bond stress-slip laws to assess their implications on transfer length and stress redistribution. Transfer length values are obtained from the normal stresses along the tendon strands and compared with those predicted by design codes. Tensile force degradation and the evolution of grout and duct compression are also analysed to characterise tendon performance under strand breakage. Results show that the strand–grout interface behaviour, together with the strands’ plasticity, plays a key role in the degraded tendon response. The study highlights the importance of detailed bond-slip modelling for assessment and monitoring of bonded tendons, providing a robust framework to complement experimental investigations and design code provisions.