Change in Compress - adding axial load calc (Bergman, ASME paper 54-A-104)

[candydu80]

Hi! I noticed in the recent Compress 7320 update, the buckling calculation due to axial load was added. The reference in Compress is Bergman's ASME paper dated 1955. Can somebody please explain why is Compress including this calc. now? The paper is 58 years old. This will affect the min. required thk. esp. on a vacuum tank. If this check is not mandatory per ASME, should there be an option to turn the Bergman calc off? If there is such option, can someone please tell me where it's at? Thanks!

 

[TomBarsh]

Actually, this is not a new feature in COMPRESS. It has been in COMPRESS since the days of COMPRESS for DOS, 25 years ago.

This check certainly can affect (govern) the required thickness of the components. Is it required by Code? Well, what does U-2(g) have to say about this, especially in view of UG-22 loadings?

We have discussed the Bergman check previously here. See these discussions:

http://www.eng-tips.com/viewthread.cfm?qid=192364

http://www.eng-tips.com/viewthread.cfm?qid=194228

http://www.eng-tips.com/viewthread.cfm?qid=219855

The paper is 58 years old, but does this diminish its utility or validity? Have the laws of physics changed abruptly? Many documents continue to be used because they have withstood the tests of time and been found to remain accurate and valid. Such documents include WRC-107 (~50 years old), the US Constitution (~225 years old), etc.

"Although this forum is monitored by Codeware it is not intended as a venue for technical support and should not be used as the primary means of technical support."

Tom Barsh
Codeware Technical Support

http://www.codeware.com

 

[jharris3]

Keep in mind also, that most of the recent Code efforts in the area of compression have been to incorporate new load combinations and new load cases that have never been included in the Code before. The methods themselves are not necessarily new and any new calculation or modification of existing Code calculation has been compared to the existing Code calculations to make sure that it provides the same or greater safety factor as in the past.

Since compressive allowable stress is based on yield and geometry the safety factor for compressive loads hasn't changed much in 58 years.

So even if Compress did not include the calculation as you see it, or if the Code did not have any reference to the axial case (which it does in Section II part D Appendix 3) you would still be required to satisfy Code safety factors for that load case and include the calculation in your design written by some other means than computer calcs.

Be careful not to assume that if the Code doesn't explicitly identify a load case or combination than you aren't required to check your design against it, because you are. That is the point that Mr. Barsh is gently making above.