Gross Plastic Deformation - too conservative or not

[Pawel27]

I would like to ask Gross Plastic Deformation users about their experience with this method. From my observation this method can be too conservative. When I consider header nozzle connection in Autopipe model results are satisfactory. Meanwhile in 3D FEM model with GPD, results are not satisfactory (5% plastic strain is exceeded). This is because in Autopipe fh+fa is allowed, meanwhile in GPD Yield strength/1.25 is used in elastic-perfectly plastic material mdoel. We use bigger allowed stress in Autopipe (EN 13480-3).
In fact GPD is for limit state, whereas fh+fa concersn "stress range" (lets say simplified fatigue analysis).
Maybe somebody use another method?