The Application of Fatigue Design Rules to Complex Fabrications

There are a number of British and U.S. codes that provide fatigue design rules for welded joints. This paper describes the basic philosophy behind these rules and discusses their application to the design of complex welded fabrications. The problems of designing in areas of geometric stress concentration and in situations where the direction of maximum principal stress is not co-incident with the weld axis, or even rotates during the loading cycle, are discussed. The paper also provides guidance on the application of finite element stress analysis to fatigue design of welded joints and the placement of strain gages on prototypes or models used for testing purposes to ensure that the calculated or measured stresses are compatible with the basic design approach.