What is Major structural discontinuity? 1

[BPVFEA]

I am referring to Cl. 4.3.10.1(b) of ASME SEC VIII Div 2 Ed. 2007 which mentions terminology "Major structural discontinuity"
I would like to know,
1) What is the definition for the term "Major structural discontinuity", and
2) Is nozzle in a shell can be called as "Major structural discontinuity"
3) Also I have read somewhere that Cone to shell junction is "Major structural discontinuity". Is it correct?
Thanks in advance.

 

[CodeRef]

Here is the definition of a "Gross Structural Discontinuity" taken directly from 2008 Edition ASME Section III,Division 1,Subsection NB, Class 1 Components.

NB-3213.2 Gross Structural Discontinuity. Gross
structural discontinuity is a geometric or material discontinuity
which affects the stress or strain distribution through
the entire wall thickness of the pressure retaining member.
Gross discontinuity type stresses are those portions of the
actual stress distributions that produce net bending and
membrane force resultants when integrated through the
wall thickness. Examples of gross structural discontinuities
are head-to-shell and flange-to-shell junctions, nozzles
(NB-3331), and junctions between shells of different diameters
or thicknesses.

FAQ731-376

 

[CodeRef]

Okay I see your dilemna...... there isn't a specific definition for a "major" structural discontinuity in VIII-2, yet there are definitions for "Gross" and "Local" structural discontinuities.

The term "Gross Structural Dicontinuity" is defined in ASME VIII-2 in two places, paragraphs 4.2.5.1(e) and 5.12(10)

The term "Local Structural Dicontinuity" is defined in ASME VIII-2 in one place, paragraph 5.12(12)

I could not find the definition for a "major" structural discontinuity in VIII-2......Could this be just another term for "Gross"? I don't know.

12. Local Structural Discontinuity – A source of stress or strain intensification which affects a relatively small
volume of material and does not have a significant effect on the overall stress or strain pattern, or on the
structure as a whole. Examples are small fillet radii, small attachments, and partial penetration welds.


FAQ731-376

 

[jmiles]

I would argue that gross and major can definitely be used interchangibly here.

 

[metengr]

I would submit an inquiry to ASME B&PV Code, Section VIII for their definition of a "major structural discontinuity" versus "gross", if a proper definition is not stated in Div 2. Nothing we say here is going to matter.

 

[TGS4]

I second metengr's reply. Ask the Code Committee what they meant. Given the amount of work that went into the new Div. 2, I would be surprised if more stuff like this doesn't pop up.

 

[BPVFEA]

Thank you all for giving valualble replies to my post.
As CodeJackal said, my dilemma was mainly due to absence of definition.
Third Party/inspection agencies are referring to such clauses and telling us include nearby components in the stress analysis which may not affect the stresses near the main component. Problem is there is no way to justify them why not to include nearby components. Only way out is FEA. This has increased considerable amount of FEA work load.

e.g As per new Div.2, definition of Gross structural discontinuity" is ;

""""A gross structural discontinuity is a source of stress or strain intensification which affects a RELATIVELY LARGE PORTION of a structure and has a SIGNIFICANT EFFECT on the
overall stress or strain pattern or on the structure as a whole. Examples of gross structural discontinuities are head-to-shell and flange-to-shell junctions, nozzles, and junctions between shells of different diameters or thicknesses.""""

Here the terms "RELATIVELY LARGE PORTION" & "SIGNIFICANT EFFECT" are not defined quantitatively/dimensionally.

 

[CodeRef]

I just discovered something funny about this whole discussion....the spelling of the word dilemma/dilemna...

Most people go with what they are taught, I was taught to spell it dilemna yet you will see it spelled as dilemma...too bad "gross" and "major" arent as similar......but I am sure you will find those that will agree they are the same......

ASME inquiry needed for sure as well as a definition if it is to be used for Code interpretation....I usually default conservatively when there is a lack of a definition in the Code words. But, I can be overrulled by the powers that are above me....

Here is a lively discussion on the word dilemma/dilemna if you are interested......

http://forum.thefreedictionary.com/postst326_Spelling-dilemna.aspx

FAQ731-376