Time-variant service reliability of post-tensioned, segmental, concrete bridges exposed to corrosive environments

This paper presents a framework for assessing the service reliability of post-tensioned (PT) bridges with damaged and undamaged tendons containing voids, chlorides, and moisture. The service reliability is defined based on the probability that the normal stress due to the applied loads (i.e., demand) at the midspan of the girder attains or exceeds the corresponding allowable normal stress (i.e., capacity). The probabilistic model to determine the normal stress demand is formulated using statistical characteristics of highway traffic and bridge design loads, probabilistic models for the tension capacity of corroding strands, the AASHTO LRFD stress model for strands, and Todeschini's nonlinear stress model for concrete. The probabilistic model for capacity is based on the AASHTO LRFD normal stress limits. Using the developed reliability framework and Monte Carlo simulation, the time-variant service reliability of a typical PT bridge over a 75-year period is estimated. After chloride and moisture infiltrate the tendons, the service reliability reduces to a value below recommended values within a relatively short period of time.