A study of primary stress indices for piping elbows

The behavior of pipe bends under moment loading is investigated in a parametric study using the elastic compensation technique for finite element analysis. The use of an Ilyushin formulation allows elastic compensation to be applied to shell elements (Boyle et al., 1993). Elastic compensation develops a lower bound limit load, which can be equated to the ASME B{sub 2} stress indices for pipe elbows. Experiments by Touboul et al. (1987) have developed formulae for normalized limit moment and the corresponding B{sub 2} indices for pipe bends in terms of the pipe parameter. This study supports the values for in-plane moment loading and suggests a modification of the formula for out of plane moments. The results for the Ilyushin formulation for elastic compensation are shown to compare well with those of a full elastic-plastic analysis.