This paper is based on work done to establish the validity of a simple engineering approach to assess plastic collapse for a vessel with a local thin area (LTA). The approach is based on a recently developed $p-M$ (internal pressure ratio and external bending moment ratio) diagram, which is an easy way to visualize the status of a vessel with a LTA simultaneously subjected to internal pressure, $p$ and external bending moment, $M$ due to earthquake, etc. If the assessment point $(Mr,pr)$ lies inside the $p-M$ line, the vessel with the LTA is judged to be safe. Numerous experiments and finite element analyses for a cylinder with an external flaw were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic initiation load and plastic collapse load by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are similar to those calculated under the proposed $p-M$ line based on the measured yield stress. The $p-M$ line adopted in the Ibaraki fitness for service (FFS) rule based on the specified minimum yield stress with a safety factor of 1.5 indicates that the safety margin for the plastic initiation loads at LTA is about 1.0–3.0, about 1.5–4.0 for the TES loads at LTA, and 2.5–6.5 for the plastic instability (break) loads.

1.
Chattopadhyay
,
J.
and
Tomar
,
A. K. S.
, 2006, “
New Plastic Collapse Moment Equations of Defect-Free and Through-Wall Circumferentially Cracked Elbows Subjected to Combined Internal Pressure and In-Plane Bending Moment
,”
Eng. Fract. Mech.
0013-7944,
73
, pp
829
854
.
2.
ASME
, 2004, B&PV Code Section VIII Div 1, UG-101.
3.
ASME
, 2004, B&PV Code Section VIII Div 2, Appendix 6, pp.
6
153
.
4.
Konosu
,
S.
, and
Mukaimachi
,
N.
, 2008, “
Plastic Collapse Assessment Procedure for Vessel With Local Thin Area Simultaneously Subjected to Internal Pressure and External Bending Moment
,”
ASME J. Pressure Vessel Technol.
0094-9930,
130
(
1
), p.
011207
.
5.
Ibaraki FSS Rule
, 2006, “
Assessment Standard for Externally Corroded Pressure Equipment
,” Ibaraki Prefecture of Japan, in Japanese.
6.
Miller
,
C. D.
, and
Mokhtarian
,
K.
, 1995, “
Proposed Rules for Determining Allowable Compressive Stresses for Cylinders, Cones Spheres and Formed Head
,” WRC Bulletin 406, Welding Research Council.
7.
Donnell
,
L. H.
, 1943, “
A New Theory for the Buckling of Thin Cylinders Under Axial Compression and Bending
,”
Trans. ASME
0097-6822,
56
(
11
), pp.
795
806
.
8.
2006 High Pressure Gas Safety Law in Japan, in Japanese.
9.
1997 “
Earthquake-Resistant Design Guideline
” High Pressure Gas Safety Institute of Japan (KHK), Report No. KHK E012–1-1997, in Japanese.
10.
Fung
,
Y. C.
, and
Sechler
,
E. E.
, 1957, “
Buckling of Thin-Walled Circular Cylinders Under Axial Compression and Internal Pressure
,”
J. Aeronaut. Sci.
0095-9812,
24
, pp.
351
356
.
11.
ABAQUS
, 2004, Finite Element Computer Program Version 6.4–1 and 6.6.2, Dassault Systemes Simulia Corp.
You do not currently have access to this content.