Concrete is a widely-used material in the construction of bridges. Currently, significant parts of the patrimony in industrialised countries are reaching the end of their lifetime. Consequently, the through-life analysis of existing concrete structures based on quantitative data is gaining attention. An important part of this is the performance prediction taking time-dependent degradation effects into account. This can be modelled using an extended Direct Stiffness Method approach.
In this contribution, an existing post-tensioned concrete bridge is considered in a probabilistic framework. The bridge is constructed in 1957 and carries highway traffic in Brussels, Belgium. Visual inspections from the bridge show severe evidence of corrosion, such as longitudinal cracks with crack widths up to several millimetres along the post-tensioning ducts. The cracks likely originate from the corroding metal ducts and/or the wires themselves. Furthermore, severe concrete spalling was observed, leaving the reinforcement and post-tensioning ducts exposed to the outside environment. In some cases, the metal duct has corroded away and broken wires can be observed.
The most severely corroded bridge girder is analysed using an extended Direct Stiffness Method (DSM) tool, circumventing the use of advanced finite element models and hence facilitating the implementation of the developed framework in daily engineering practice. Therefore, the traditional DSM approach is extended to accommodate for (corroded) post-tensioned elements. A probabilistic framework is constructed which is able to predict the reliability index of the element, as well as the end-of-service life of the girder. Currently, the considered bridge is part of a large-scale monitoring campaign, continuously measuring the strains along the bridge. Hence, the approach is coupled with Bayesian updating, which can reduce the uncertainties on the input and output of the DSM tool. As a result, more accurate predictions can be made of the structural performance of the girder, contributing to the decision-making process regarding the considered bridge.