Fracture Control Guidelines For Welded Steel Ship Hulls

The Report provides comprehensive toughness criteria for welded ship hulls that can be used for steels of all strength levels. Because of the fact that stress concentrations are always present in large complex welded structures and therefore high stresses as well as discontinuities or flaws will be present in welded ship hulls, primary emphasis in the proposed fracture-control guidelines is placed on the use of steels with moderate levels of notch-toughness and on the use of properly designed crack arresters. In general, concepts of fracture mechanics are used to develop the material toughness level that is required for fail-safe operation of welded ship hulls.

The purpose of this report is to review in the light of currently existing data the fracture-toughness guidelines for welded ship hull steels first proposed in 1974. The essence of the guidelines was an NDT temperature requirement of 0 deg F for steel used in primary load-carrying members and an NDT temperature requirement of 20 deg F for steels used in secondary load carrying members. A subsidiary requirement for primary members was a dynamic tear energy in 5/8 in. specimens, depending on steel strength, of 250 to 500 ft-lb. at 75 deg F. Crack-arrest materials would be required to have a dynamic tear energy in 5/8 in. specimens, again depending on steel strength, of 600 to 800 ft-lb. at 32 deg F.

This report provides an introduction to the elements of fracture mechanics for bridge design. Fracture mechanics concepts are introduced and used as the basis for understanding fatigue and fracture in bridge structures. Various applications are cited.