Dear Friends,

According to B31.8 paragraph 833.9:

"High local stresses are usually generated at structural discontinuities and sites of local loadings. Although they may exceed the material yield strength, such stresses may often be disregarded because they are localized in influence and may be self-limiting or relieved by local deformation. Examples include stresses in branch connections caused by pressure or external loads, or stresses at structural discontinuities. This Code does not fully address the maximum allowable value for local stresses. It is the engineer's responsibility to determine whether such stresses must be evaluated."


I'm analyzing special pipeline support using ANSYS workbench in the hydro test, operating, and design conditions. By considering the elastic behavior for the material, near the wear pad, and its welds, Von Misses stresses in some nodes are more than twice the tensile stress of the material due to bending through-wall. But by considering elastic-plastic behavior for the pipeline, welds, and support, local pipeline and weld stresses are between yield stress and tensile stress of the material.

I have three questions in this regard:
1- Is it a valid assumption to consider elastic-plastic behavior for the pipeline, welds, and support material according to piping and pipeline codes?
2- If the above-mentioned assumption is a valid assumption, what is the allowable membrane, bending through-wall, and Von Mises stress for local stress in each load case such as hydro-test, operating, etc?
3- Are the requirements of ASME Sec. VIII Div. 2 Part 5 applicable for piping and pipeline local stresses evaluation?