State-of-the-Art Fracture Characterization. I: Master Curve Analysis of Legacy Bridge Steels

Advances in the field of fracture mechanics over the last four decades have allowed for a greater understanding of brittle and ductile fracture, including how to account for plasticity in fracture specimens and how to statistically define data scatter in the brittle and ductile-brittle transition region. This is particularly important for structural steels used in bridge applications, which typically possess high ductility and toughness. The material toughness provisions of the fracture control plan for highway bridges in the United States were developed from a database of linear-elastic tests, many of which were considered to be invalid according to testing standards in place at the time. This, the first of two companion papers, presents a reevaluation of legacy fracture toughness data obtained from steels used in highway bridges. This reevaluation uses plasticity corrections that characterize the toughness behavior of these steels using the master curve approach. Results of the study indicate that the master curve approach can be used to accurately describe the temperature dependence and associated scatter of fracture behavior in the ductile-brittle transition region of historic bridge steels. This can be used to define cleavage fracture tolerance bounds for a given data set, which is a necessary step toward the development of a performance-based fracture design specification.