Corrosion effects on bond between strand and concrete in pre-tensioned members: analytical modeling of transmission length

Corrosion in pre-tensioned members causes loss of prestressing and worsening of strand mechanical characteristics. Moreover, it can lead to concrete cracking or wire breaking. These effects influence the bond between steel and cementitious matrix, which, in pre-tensioned concrete elements, plays a fundamental role in the whole performance of the structure. Bond is indeed responsible for the transmission of the initial prestress and, therefore, its variation directly reflects on the beam behavior. In this paper, a novel approach is proposed to model the bond strength in presence of corrosion. Particular attention is paid to the transmission length evaluation, through a proposal of an analytical model able to include the effects of corrosion. Thick-Walled Cylinder theory is applied to simulate the behavior of the corroded strand close to the beam ends. Simulation results show that corrosion has remarkable consequences on bond, inducing a strong increase in transmission length after a corrosion ratio of 7.00%. These outcomes are consistent with experimental evidence found in the literature.