Numerical evaluation of corrosion effects on the flexural behaviour of post-tensioned concrete bridge girders with defective grouting

In post-tensioning technology, tendons designed to bond with concrete are placed within ducts that are typically grouted with cement mortar after tensioning. Inadequate or discontinuous grouting can lead to corrosion of prestressing steel, significantly affecting the structure's mechanical performance and durability. This paper presents a comprehensive numerical investigation into the impact of corrosion on the flexural response of post-tensioned (PT) concrete bridge girders under varying grouting conditions and initial prestress levels. Experimental tests on PT girders with uncorroded strands were used to calibrate finite element models (FEMs). These tests included six girders with three distinct grouting conditions—bonded, unbonded, and partially bonded—and two different initial prestress levels, along with two additional girders featuring variable prestress levels and damaged tendons. The calibrated FEMs were then extended to incorporate corroded stress–strain relationships for the tendons, simulating three increasing levels of corrosion severity. The study examines the interaction between grouting defects, prestress levels and corrosion-induced degradation, in girder response at both local and global scales, including midspan deflection, force–displacement behavior and stress distribution. Results indicate that local defects reduce the load-carrying capacity of girders more than global defects due to increased strain demand in partially bonded configurations. Corroded tendons can also produce a transition from ductile to brittle flexural failure mode, potentially causing premature rupture of the uncorroded tendons. Moreover, comparisons between damaged and corroded tendons reveal that a severe corrosion scenario can simulate the effects of local rupture, causing girders to behave as if the tendon was cut. Based on these findings, an analytical formulation is proposed to estimate the load-carrying capacity of girders with corroded tendons and varying bonding conditions. This work provided a comprehensive study on the influence of corrosion on PT concrete bridge girders with simplified analytical models for capacity assessment.