Finite Element Analysis of Chloride Ingress in Prestressed Concrete Bridge Girders Accounting for Service-Life Ambient Conditions

Abstract

This paper introduces a computational simulation scheme to describe the intrusion of corrosion-inducing chloride ions in prestressed bridge girders. This phenomenon impacts the durability of bridges in coastal zones or regions where deicing salts are used. The computational study is focused on two girders decommissioned from separate bridges in Virginia after 34 and 49 years of service. A time-dependent, nonlinear finite element scheme, accounting for coupled heat, moisture, and chloride transport, is formulated and used in the analyses. The model parameters are calibrated using data from material tests in the literature. Subsequently, two-dimensional analyses are conducted to determine the evolution of chloride in the girder cross-sections. Contrary to earlier studies using finite element analysis, which have been focused on laboratory specimens, the work presented herein is focused on reproducing the evolution of chloride ingress of actual bridge members, considering the local climate conditions through the use of temperature and relative humidity measurements from weather stations in the vicinity of the bridges. The simulations are found capable of capturing the actual chloride content at various depths from the surface, measured through titration tests. Further analyses indicate that using the simplified, design-oriented equations in the fib code may underestimate the chloride content during the lifespan of a bridge. A similar underestimation is observed if the impact of advective chloride transport is neglected in the finite element models.