Bond Strength Model of Strand in Corrosion-Induced Cracking Concrete

This paper presents an analytical model to predict the evolution of strand bond strength with the propagation of concrete corrosion cracking, in which the transition of bond failure modes from pullout failure with strand rotation to concrete splitting failure is considered. For both failure modes, the ultimate bond strength is determined from the contributions of adhesion, corrosion pressure, and maximum confinement by considering the helical characteristics of seven-wire steel strand. The corrosion pressure in the untracked, partly cracked, and completely cracked stages is estimated based on the relationship between radial displacement and pressure at the strand-concrete interface. For the contribution from maximum co n finement, a critical confining stress is applied for the pullout failure type to consider the effect of strand rotation. The predicted results are shown to reasonably reproduce the variation tendency of strand bond strength and experimental results for specimens with and without stirrups. For the pullout failure type with strand rotation, introduction of the critical confining stress limits overestimation of contributions of confinement to the ultimate bond strength, especially for the corroded specimens with stirrups after complete cover cracking.