scope:

A general fatigue analysis procedure is provided in WRC Bulletin 474 that can be used for life estimation for structures containing welded joints under arbitrary loading conditions. For variable amplitude loading, conventional cycle counting methods and Miner's rule summation of damage can be applied. The method is general and can also be used with other cumulative damage theories, structural reliability methods and probabilistic analysis, etc. The mesh-insensitive structural stress method discussed in this document provides a robust calculation procedure for capturing the stress concentration effects on fatigue behavior of welded joints. Its effectiveness is demonstrated by not only consolidating the pipe weld S-N data relevant to ASME codes, but also consolidating the pipe data with plate joint data collected from drastically different thicknesses, loading modes, and joint configurations. The mesh-insensitive structural stress method is developed based on equilibrium considerations by extracting equilibrium-equivalent membrane and bending components at a weld, where severe stress concentration can induce significant variations in conventional FE stress calculation methods. In doing so, the structural stress parameter can be viewed as an equivalent far-field stress in fracture mechanics context. Thus, an effective fatigue damage parameter can be formulated in the master S-N curve approach presented