Static load case

Hellow

I have only one year of experience in stress analysis and in Caesar II, and I have many doubts, I hope that my questions aren´t too stupid, please sorry...I´ll try to explain it

I have been trying to analyze a 20" diameter A106-B,in a termical plant,at 400ºC and 0.2bar. The pipeline is inside a build and due to this condition there isn´t wind load case and there isn´t seismic load, because isn´t a seismic zone, and I haven´t ocassional loads.
I only have simple load W,P,T and D1 and D2 due to conected equipments desplacements to pipeline, and using CODE ASME B31.3:

L1: WW+HP (HYD)
L2: W+P1 (SUS)
L3: W+T1+P1+D1 (OPE)
L4: W+T1+P1+D2 (OPE)
L5: L3-L2 (T1+D1) (EXP)
L6: L4-L2 (T1+D2) (EXP)
L7: L3-L5 (EXP)
L8: L4-L6 (EXP)

Please this combination are correct?

Thank you four your help

Best regards
Nala

L7 & L8 is not an expansion stress.. its sustain stress.

And im not sure if its okay to do HOt sustain in this way... instead i will suggest, add separate L7=T1+D1(exp) & L8=T1+D2(Exp) and minus it with L3 & L4,. L9=L3-L7(sus) & L10=L4-L8(sus). as basic guide in CaesarII tech reff.

But Lets See what Sir Rich can say about the case of hot sustaining your L7&L8.

Regards,

If you're after the "hot sustained" stresses then this is what you want:

L1: WW+HP (HYD)
L2: W+P1 (SUS)
L3: W+T1+P1+D1 (OPE)
L4: W+T1+P1+D2 (OPE)
L5: T1+D1 (OPE) {construction case only}
L6: T1+D2 (OPE) {construction case only}
L7: L3-L2 (T1+D1) (EXP)
L8: L4-L2 (T1+D2) (EXP)
L7: L3-L5 (SUS)
L8: L4-L6 (SUS)

Sir Rich, To save space for other cases can we just do {(L3=W+T1+P1+D1[Ope])-(L7=L3-L2(T1-D1)[exp]}(hot sustain)? As in my previous post... Im not sure with this but can you explain the difference of using construction cases and not using?

Regards,

Hellow

Thank you very much for all your clarifications

I have a question about the differents case for Static load case, this is when a hanger is in a pipeline. The pipeline is the same, 20" diameter and A-106B material,and there isn´t wind load case and there isn´t seismic load case. I only have simple load W,P,T,D1 and H (for a hanger).

Please, help me, what is the correct static load case for this case?

Thank you very much.

Best regards.

Nala.

Bom - I don't typically avoid "combinations of combinations". I'd rather have more "simple" load cases than fewer really complex ones - much easier to diagnose the cause of problems in the system if the load cases are simple.

Nala - Push the [Recommend] button, the cases c2 develops should be sufficient.

Sir Rich,

Again and as always, thank you very much.

Regards,

Dear Richard,

What is the difference between sustained stress and hot sustained stress? What is the necessity of it and when and in what situation we need to consider it? Normally, we are not using such load cases, please clarify.

Dear all,
I'm very curious to read the answer regarding to paldex's question.
I've other doubts about static load cases.
I'm studying an FRSU plant and I've to consider a lot of cases. I've to take in account the effect due to accelerations Ax Ay Az (condition of rolling, pitching ....),structure dispacements and wind.
Note that wind is always concurrent with Ax or Ay and acceleration mustn't be considered occasionals.
Regarding SUS condition, I don't think W+P1 is the only one to take in account; I've to consider for example this condition with all its combinations:
W+P1+D1+U1+0.5U2+U3+WINx
where D1--->structure displacements
U1--->Ax
U2--->Ay
U3--->Az
Are you agree with me?

The principal doubt I have is: if I mustn't consider Ax,Ay,Az as occasional and also displacements and wind aren't to consider occasional, because they come from or are contemporary with acceleration, is more right to consider W+P1+D1+U1+0.5U2+U3+WINx as SUS condition or in anycase I've to consider it as OCC condition?

If the answer is 'You have to consider it as SUS', won't there be OCC conditions in my statistic load case?

Regards
Best regards

Please use the search function in the forum to get an answer, it's discussed numorous times. It basically has to do with differences in primary stresses in cold and hot situation due to different supporting positions. This can happen when you're using non-lineair restraints.

What you want to check in your sustained case are the primary stresses in the network during operation. That's why you compare the stresses with the allowables at the design temperature. You calculate the stresses using W+P for your sustained case. Now if for example during operation a supports lift off due to thermal expansion, one of the supports is "taken away" from your setup and thus changing the distribution of primary stresses (stresses due to weight). Compare it with a steel beam on 3 supports each at a distance of 5 meters, and then taking the middle support away.

The situation where you calculate the primary (sustained) stresses using only the supports that are supporting the pipeline during operation is called the "hot-sustained".

I guess your concern should be "fatigue".
Counting just constant occasional or "non-occasional" accelerations it’s a good chance that your FRSU would go faster and faster... and quickly to a disaster.
This difference between pseudo-kinematics and fatigue (the last being in the end-chapters of some books...) would be a good lesson learnt for your Client.

Best regards,

Thankyou very much Mr.Corne for your reply and solution.

Dear all,

I'm analyzing an indoor piping system in an earthquake zone. Would you please quote your helpful comment on the following static load cases!
I prepared it according to the Coade guideline but it was based on WIND and just I changed the wind to earthquake load. I'm not sure if it is correct because wind condition sometimes is stable, but earthquake is an occurrence.


L1: WW+HP HYD
L2: W+T1+P1 OPE
L3: W+P1 SUS
L4: W+T1+P1+U1 OPE
L5: W+T1+P1+U2 OPE
L6: L4-L2 OCC
L7: L5-L2 OCC
L8: L2-L3 EXP
L9: L3+L6 OCC
L10: L3+L7 OCC

cheers,

Assuming U1 and U2 represent the seismic loadings for two different conditions (directions), then "yes" these load cases are satisfactory.

I recommend you (and not only you) the Sam Manik’s "Load Cases" document in the "Temperature Inputting" topic just bellow this one...by a strange coincidence has been "reactivated" by a people not speaking English…in the same note you can say "Terima kasih\ ‘makasih\ - or better- Thank you, Sam Manik"…

About your concern...both "static earthquake" and "static wind" are approximations of dynamic phenomena. For earthquake it’s a little bit more evident this fact (especially for people that have experienced a strong earthquake). About the wind...Tacoma Narrows Bridge has collapsed because aerodynamic flutter at a wind of 42mph; after the collapse, new mathematical theories of vibration, aerodynamics, wave phenomena, and harmonics have been applied to bridge design.

Dear all,
I' don't know if it's the right thread to write this; I'm sorry if I'm wrong.
Is there anyone who can clarify the following request? If I've to analyze a system in which I've to consider displacements, how can I create the cases regarding hanger design?
Example
W+P1-->SUS
W+P1+D1+D3+T1-->OPE
W+P1+D1+D4+T1-->OPE
W+P1+D1+D5+T1-->OPE
W+P1+D2+D3+T1-->OPE
W+P1+D2+D4+T1-->OPE
W+P1+D2+D5+T1-->OPE

where D1 and D2 come from thermal displacements, D3 D4 D5 are due to structure movements.

So the conditions for hanger design is:

W-->HGR
W+P1+T1-->HRG
W+P1-->SUS
W+P1+D1+D3+T1+H-->OPE
W+P1+D1+D4+T1+H-->OPE
W+P1+D1+D5+T1+H-->OPE
W+P1+D2+D3+T1+H-->OPE
W+P1+D2+D4+T1+H-->OPE
W+P1+D2+D5+T1+H-->OPE

Is it right? Or I've to do in the following way:
W-->HGR
W+P1+D1+D3+T1+H-->HGR
W+P1+D1+D4+T1+H-->HGR
W+P1+D1+D5+T1+H-->HGR
W+P1+D2+D3+T1+H-->HGR
W+P1+D2+D4+T1+H-->HGR
W+P1+D2+D5+T1+H-->HGR
W+P1-->SUS
W+P1+D1+D3+T1+H-->OPE
W+P1+D1+D4+T1+H-->OPE
W+P1+D1+D5+T1+H-->OPE
W+P1+D2+D3+T1+H-->OPE
W+P1+D2+D4+T1+H-->OPE
W+P1+D2+D5+T1+H-->OPE

I hope someone can help me to solve my doubt and I'm sorry if it can appear stupid.

Best Regards

Many thanks Sir Richards and Mariog. it was so helpfull.

Honestly, the pdf file/document "load cases" I got from Coade. So many thanks to them ...

You have a remarkable determination to skip the basics….and I’m stubborn enough to continue recommending: PLEASE review the "Load Cases" document, is a good guide on the subject.
Probably one point you are missing is the fact Spring Hanger is physically a (special) support but is rather a force for the calculation. Now it makes sense for you to have H in both OPE and SUS, but not in HGR (where H is resolved)?
So please review the basics, otherwise you’ll have for ever such doubts!

Best regards,

Simply go to the link below and download the pdf file there:
http://www.coade.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=19663&page=1#Post19663

And please learn the basic concept of:
-Load Cases with Hanger Design
-Load Cases with Thermal Displacements

Combined these both basic concepts using your creativity.

Dear Mariog, I don't want to be ill-mannered, but your attitude is really annoying! I'm not so stupid to continue to skip the basics! I know 'Load case' document and I repute it very useful. If you note in 'Load Cases with hanger Design' both in OPE and in SUS we find H. But it isn't what I asked. I want to know, since it isn't written, how I can create the two first cases in presence of structure displacements. Are they the same which there are on the document or have I to do in a different way?
For example:
Will the second case W+T1+P1 be the same or W+P1+D1+T1, W+P1+D2+T1....for each displacement?

Now, if you want to help me, I'm really happy; but if you have to answer in a bad way as you did, please don't reply. I'll wait for other user's reply which will be more useful.

Best regards

Dear Italtecnica,

Yes any displacements are the same. Please combine which are possible acting together. You can take the reference in case:
-Load Cases with thermal displacements and settlement
-Load Cases with Pitch and Roll

Well, maybe is true you are not ill-mannered, and my attitude is really annoying you! But this is really a secondary matter.

It's clear you make serious efforts to think about and this is good.

You say you've read "Load Cases" and this is also good.

Once, Mr Luf said "It is often wise not to argue with people who think they have the answer.... let them test their skills and see what happens,,, it may mean the work will go to those who are more competent in the end."

So forget my recommendations and just go ahead, I’m not saying you are on the wrong way!