Probabilistic Analysis of Brittle Fracture Design Code Provisions for Steel Bridges

Abstract

Brittle fracture is a major concern to structural engineers, as it can have significant consequences in terms of safety and cost. Although modern day occurrences are rare, it is well known that brittle fracture 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. A previous comparison of brittle fracture design provisions around the world revealed that more sophisticated approaches are available in terms of modelling and understanding brittle fracture in existing and new bridges than the simple design approaches currently used in North America. One of these procedures is the fracture mechanics method in the European EN 1993-1-10 standard. This paper describes this method and extends it to a probabilistic framework using Monte Carlo Simulation and the example of a typical steel-concrete composite highway bridge. Input parameters are varied, such as plate thickness and applied loading, and failure probabilities are generated. Based on the results and the sensitivity of the failure probability to variations in each parameter, the paper discusses potential areas of improvement in the current Canadian standards for brittle fracture.