Session: CS-36-01 Combined Session: Master Curve Method and Applications, and Improvement of Flaw Characterization Rules for Fitness for Service

Paper Number: 61989

Start Time: Thursday, July 15, 2021, 09:00 AM

61989 - Improvement and Assessment of the Plastic Collapse Bending Moment Equations in Circumferentially Cracked Pipe 

The plastic collapse bending moment in a pipe cross-section with a circumferential crack is defined in ASME B&PV Code Section XI, Appendix C using simplified equilibrium equations by approximating the pipe mean radius R_m and the neutral axis angle β. In previous papers it was demonstrated by the authors that, for external cracked pipes, those simplified equilibrium equations are not conservative and hence improved equations were developed and proposed accounting for the cracked pipe ligament mean radius R_mc.

In this paper, it is demonstrated that the accuracy of the collapse bending moment equation can be refined by taking into account the exact neutral axis position Y_na of the cracked pipe section. This leads to exact collapse bending moment equations without any approximation on the pipe mean radius R_m nor on the neutral axis angle β.

In this frame, it is shown in the paper that, for external cracked pipes, the ASME B&PV Code Section XI, Appendix C equations could lead to more than 30% less conservative collapse bending moment than with the exact equations. In addition, an extended finite element method analysis completes this study to assess the relevance of the model used to determine the plastic collapse bending moment.

Presenting Author: Cécilia Desclaux Tractebel (Engie)

Authors:

Cécilia Desclaux Tractebel (Engie)
Valery Lacroix Tractebel (Engie)
Kunio Hasegawa Japan Atomic Energy Agency