Reliability analysis of post-tensioned concrete bridges using inspection-based modelling of grout injection voids

Corrosion of prestressing steel in post-tensioned (PT) cables is a critical issue in prestressed concrete bridges, often leading to brittle and unexpected failures. This deterioration is primarily attributed to construction flaws such as inadequate grout injection and the use of poor-quality mortar. This paper presents a probabilistic model for estimating the number and spatial distribution of grout defects in PT girders, developed using inspection data from a large sample of existing bridges in Italy. The model is integrated into a spatial and time-dependent system reliability framework to assess the remaining technical service life of PT structures. Application of the proposed method to a representative PT bridge deck shows that conventional reliability analyses, which often assume worst-case defect placement, may be overly conservative. In contrast, the developed approach, which accounts for spatial randomness in defect location and time-dependent degradation, can lead to significantly extended service life estimates (∼30%).