The Effect of D/T on the Load Interaction Behavior of a Plain Pipe

2004 ◽  
Vol 126 (4) ◽  
pp. 518-522 ◽  
Author(s):  
Amran Bin Ayob
Keyword(s):  
Internal Pressure ◽  
Effective Stress ◽  
Axial Force ◽  
General Trend ◽  
Bending Moment ◽  
Design Codes ◽  
Yield Behavior ◽  
Combined Loads ◽  
Interaction Behavior ◽  
Von Mises

The objective of the study is to determine the effect of diameter/thickness (D/T) ratio on the interaction of axial force, bending moment, torsion and internal pressure in plain pipes. The Tresca and von Mises criteria are used to determine the first yield behavior of pipes when subjected to combined loads. The results show that for certain load combinations, the load interaction behavior is affected by D/T ratio and some load interaction relations change with a load dominance. The general trend is an increase in effective stress as D/T is increased. Most design codes show slightly conservative pipe design.

Study on Limit Load of Orthotropic Cylindrical Pipe Under Different Combined Load Conditions

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Min Xu ◽  
Jian-bin Wen ◽  
Yu-jie Zhao ◽  
Chang-Yu Zhou ◽  
Xiao-hua He
Keyword(s):  
Yield Strength ◽  
Internal Pressure ◽  
Axial Force ◽  
Shear Force ◽  
Bending Moment ◽  
Limit Load ◽  
Cylindrical Pipe ◽  
Load Combination ◽  
Combined Loads ◽  
Torsion Moment

Abstract In engineering, many pressure pipes are made of steels with good plasticity, which are subject to internal pressure, axial force, shear force, bending moment, torsion moment or their combined loads. The plastic limit load is an important indicator of the load capacity of pressure pipe. According to Hill yield function, the theoretical solutions of limit load of orthotropic cylindrical pipe under various combined loads under internal pressure, axial force, shear force, torsion moment, and bending moment have been derived on the basis of elastic perfectly plastic constitutive model. The effects of radial stress on different combined limit loads of cylindrical pipe are explored and these results show that the radial stress should be considered about the limit load calculation especially for thick-walled cylindrical pipe. The interactions of various load combination are analyzed in detail and drawn with the interaction curves. For isotropic cylindrical pipe, the limit load increases with the yield strength. For the orthotropic cylindrical pipe, the limit loads of cylindrical pipe under axial force, bending moment, shear force, and torsion moment without internal pressure are only related to the axial yield strength. The limit bending moment is mainly dependent on the axial yield strength when internal pressure is lower, while the impact of the circumferential yield strength of orthotropic cylindrical pipe is obvious when internal pressure is some higher. When the axial yield strength of orthotropic cylindrical pipe is the same, the circumferential yield strength can enhance the limit axial load, limit torsion moment, and limit shear load. Under the different load conditions including internal pressure, bending moment, axial force, shear force, and torsion moment or their combined loads, the relation of limit bending moment with yield strength ratio is diverse, which is decide by the load combination, the circumferential yield strength, and the axial yield strength.

The Assessment of Locally Thinned Areas Subject to a Hoop Stress and an Axial Stress: Background to the Guidance Given in Annex G of BS 7910:2013

2019 ◽  
Author(s):  
Andrew Cosham ◽  
Robert Andrews
Keyword(s):  
Internal Pressure ◽  
Axial Force ◽  
Hoop Stress ◽  
Axial Stress ◽  
Bending Moment ◽  
Full Scale ◽  
Plane Bending

Abstract Annex G Assessment of locally thinned areas (LTAs) in BS 7910:2013 is applicable to LTAs in cylinder, a bend and a sphere or vessel end. It can be used to assess the longitudinally-orientated LTA in a cylinder subject to a hoop stress and a circumferentially-orientated LTA in a cylinder subject to an axial stress (due to axial force, in-plane bending moment and internal pressure), and also to assess an LTA subject to a hoop stress and an axial stress. An outline of the origins of Annex G is given. A comparison with full-scale burst tests of pipes or vessels containing LTAs subject to a hoop stress and an axial stress is presented. It is demonstrated that the method in G.4.3 Hoop stress and axial stress is conservative.

Mobilization of Fully Plastic Moment Capacity for Pressurized Pipes

1999 ◽  
Vol 121 (4) ◽  
pp. 237-241 ◽  
Author(s):  
M. Mohareb ◽  
D. W. Murray
Keyword(s):  
Internal Pressure ◽  
Axial Force ◽  
Yield Criterion ◽  
Axial Loading ◽  
Experimental Results ◽  
Moment Capacity ◽  
Interaction Diagram ◽  
Von Mises ◽  
Force Pressure ◽  
Good Agreement

An analytical expression is derived for the prediction of fully plastic moment capacity of pipes subjected to axial loading and internal pressure. The expression is based on the von Mises yield criterion. The expression predicts pipe moment capacities that are in good agreement with full-scale experimental results. A universal nondimensional moment versus effective axial force-pressure interaction diagram is developed for the design of elevated pipe lines.

Study of Bending Capacity of an HPHT CRA-Lined Seamless Pipeline

2014 ◽  
Author(s):  
Cyprian Gil ◽  
Knut Tørnes ◽  
Per Damsleth
Keyword(s):  
Internal Pressure ◽  
Strain Localization ◽  
Local Buckling ◽  
Bending Moment ◽  
Design Criteria ◽  
Design Codes ◽  
Moment Capacity ◽  
Wide Range ◽  
Global Buckling ◽  
The Moment

A study has been performed to better understand ultimate bending moment and strain capacities of pipelines in relation to criteria defined in the design codes. An 18″ HPHT flowline was designed to undergo global buckling on uneven seabed and to resist trawl gear interference. The high temperature (155 degC) and pressure (300 bar) posed considerable design challenges for material selection and design criteria. A CRA-lined X60 CMn pipeline was selected for the project. The pipeline was of seamless manufacture for which the stress/strain characteristics are subject to the effect of Lüders bands. The DNV-OS-F101 code covers a wide range of D/t but does not specifically address Lüder’s material behaviour which could significantly reduce the bending moment capacity of pipe. The global buckling and trawl pull-over FE analysis results indicated the pipe was highly utilized, requiring excessive amounts of seabed intervention at great cost to meet the DNV LCC criteria. Detailed FE simulation of limit states for local buckling and strain localization of a 3D solid element pipe model was performed, with both Roundhouse and Lüders material properties, to investigate pipe capacity in relation to that stipulated by the design codes. The pipe moment capacity was established by obtaining the moment curvature relationship by bending the local pipe section subject to internal pressure until the maximum resistance was reached. Imperfections were introduced to initiate local buckling at the desired location. To determine strain concentration factors and strain localization, the effects of thickness changes and weld misalignment were also studied. The DNV OS-F101 LCC moment criterion formulation computes a decreasing moment capacity for increasing internal pressure. It has been suggested in the literature that this is correct for higher D/t but the criterion may be conservative for pipes with lower D/t. The combination of Lüders material with low D/t is not specifically addressed by any design code. Clarification of these aspects will provide a better understanding of the risk of failure for highly utilized seamless pipelines and allow for modified design criteria that will reduce seabed intervention costs. The results of the study showed that a higher bending moment criterion and associated strain criterion could be adopted for the design that allows for the higher initial strain caused by Lüder’s plateau. The ultimate bending moment capacity of low D/t pipe with Lüder’s material was found to be similar to that of Roundhouse material due to work hardening. In addition, it was demonstrated that the potential strength of the CRA liner could enhance the moment capacity of the seamless pipe.

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