Posted by: ANON
hot sustained stress - 06/04/08 06:52 AM
Hi ,
I am making a load case for hot sustained stress as detailed in the CII documentation
W+P1+T1(OPE)
W+P1(SUS)
T1 (EXP)
L1-L2(EXP)
L1-L3(SUS)
The combination method for L1-L2(EXP)stresses is ALGEBRAIC.What should be the combination method for the hot sustained stresses ALGEBRAIC or SCALAR.
Thanks in advance
ANON123
Posted by: Richard Yee
Re: hot sustained stress - 06/04/08 08:45 AM
ANON,
The L2 load case is your hot SUS case, I think.
Posted by: machoguy
Re: hot sustained stress - 06/04/08 05:35 PM
Richard,
The L2 load case is the cold sustained case.
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Machoguy
“Science without religion is lame, religion without science is blind."
Posted by: Richard Ay
Re: hot sustained stress - 06/04/08 06:19 PM
W+P1+T1(OPE) - standard operating
W+P1(SUS) - standard (cold) sustained
T1 (EXP) - construction load case - don't use this for anything
L1-L2(EXP) - standard expansion
L1-L3(SUS) - hot sustained
Posted by: Richard Yee
Re: hot sustained stress - 06/05/08 11:46 AM
To ANON and machoguy and Richard Ay,
I got someone to bite on the hook!
Let me choose my words carefully. The SUS sustained case stresses are calculated for the piping in the installed position, and compared to the material's Hot allowable stress.
In a perfect world the piping would stay on the supports, and constant spring supports would maintain the same force on piping. In the real world there are some supports that lift off, and spring supports have some variability. So there is the question of what are the sustained stresses when the piping has moved to the operating position?
Some would remove the 'lifted' supports from the analysis. Others say the piping could yield and set down at the location of a lifted support. It is not a simple answer. If a support is removed, the SUS installed stress could then exceed the allowable. Also, the loads would be re-distribued such that other supports might then lift off. Have you seen supports that carry no load, in the installed case but then same support has load in the operating case? Would that be the inverse of the 'lift off' condition?
The L1-L3 load case should be viewed with some skepticism. The components of L1-L3 when shown as algebraic [W+P1+T1] (-) [T1] = W+P1 , and someone might wonder if there is anything gained between the two.