Fracture and Fatigue Control in Steel Structures

Considerable effort has been devoted to the prevention of brittle fracture in manufactured structures such as aircraft and pressure vessels, where large numbers of essentially identical structures are fabricated under closely controlled conditions. For example, the emphasis on safety and reliability of nuclear pressure vessels and the ensuing extensive research, as well as stringent controls, have led to a situation where the probability of a brittle fracture in a nuclear pressure vessel is virtually zero. For other types of manufactured structures, the causes of field failures usually can be remedied by changes in design of subsequent units. In contrast, other types of structures, such as bridges and buildings, are often individually designed for a specific function and location. The overall service experience of steels in these structures has been excellent, so that the designer in the past has seldom concerned himself with notch-toughness as a design parameter. However, the trend in structural design has been such that the following changes have occurred.