Allowable Moment
Each of the components typically found in a piping system needs to be included.
Straight pipe – Use a curvature based buckling criterion selected from the text book “Piping and Pipeline engineering” by George Antaki (Chief Nuclear Engineer of Becht Engineering). This criterion is in use in subsea pipeline laying operations. It imposes a limit on the plastic strain in the pipe from which a bending moment can be calculated.
Elbows – apply a geometry-dependent multiplier on the allowable pipe moment using method published in Teschniche Mechanik, “Load Bearing Capacity of Thin Shell Structures Made of Elastoplastic Material by Direct Methods” by Tran et al. This multiplier method was developed from a series of elastic-plastic Finite Element Analysis (FEA) simulations.
TEEs – use elbow moment results and apply Sustained Stress Index (SSI) published by ASME, “PVP2014-28267 Sustained Stress Indices (SSI) in the B31.3 2010 Edition” by Paulin et al. Simplified, the SSI can be said to be to collapse what Stress Intensification Factor (SIF) is to fatigue.
Flanges – use allowable flange moment from the Koves' method published by ASME, “Analysis of Flange Joints under External Loads”, W.J. Koves. The Client also asked to include their own internal assessment procedure for allowable flange moment. Select the highest allowable moment to be governing.