Time-Dependent Probabilistic Analysis of Steel Bridge Brittle Fracture

Brittle fracture is a major concern to structural engineers as it has significant consequences in terms of safety and cost. Although modern day occurrences are rare, it is well known that they can occur without warning and may lead to the sudden closure of a bridge, loss of service, expensive repairs, and/or loss of property or life. In Canada, steel bridge fracture is a more significant concern due to the harsh climate, which, if the toughness properties are improperly specified, could put many steels on the lower shelf of the toughness-temperature curve. In the existing CSA standards, design against brittle fracture solely depends on the temperature of the location of interest, and other factors impacting fracture, such as stress level and plate thickness are currently neglected. A previous comparison of brittle fracture design provisions around the world revealed that more sophisticated approaches have been developed in terms of modelling and understanding brittle fracture than the ones currently in use in North America. One of these procedures is the fracture mechanics method in the European EN 1993-1-10 standard. This paper briefly describes this method and then shows how it can be implemented in a probabilistic framework, using historical temperature and truck data to determine the failure probability with respect to temperature and traffic loadings fluctuating on a time scale throughout the year.