Dear All,

Good Day. This is my first post.
I am working on a flexibility analysis of a circular steam ring (distributor) in a reactor. During the analysis I found that some supports are in-active, so a Hot-sustain case is required to pass, by removing those +Y (in-active) manually and run SUSTAINED case alone. Sustained allowable stress for this work is 11MPa. During this manual hot-sus I am getting induced stresses as 16MPa (>11MPa). For the same project, I added ALT-SUS for my four operating cases individually (referred from CAESAR User Guide). In this ALT-SUS case, all induced stresses are below 11MPa (requirement achieved). But my costumer asking me to show <11MPa in manual hot-sus, instead of ALT-SUS.

Hope you understood my situation. So, can anyone tell me how can I compare the manual hot-sustain and ALT-SUS (Auto hot-sus check in CAESAR)?

Also I think that, ALT-SUS deducing its values (stresses) for individual operating case and manual hot-sus is some what different to that.

Hope I may get some answer on this ASAP.

Regards,
Gautham Ajay.

ALT-SUS does not necessarily produce the same results as the "hot sustained" analysis. (hot sustained = operating - expansion)
For your manual hot-sustained case you say you removed the +Y's that were inactive in the operating case. ALL nonlinear restraints would be set to that operating state. This includes closed gaps on guides. Perhaps these overlooked restraint setting cause the difference? At the moment I cannot say how friction is handled here.

Thank you Dave.
Regrets for the delay in my response.
In the same analysis, the gaps introduced are (+Y=0 & Mu=0.3, guide in +/-Z with gap of 3 and 20mm and about -Y=0) but for -Y I didn't assigned any value to Mu. Is it okay? Because even if I give 1mm gap in -Y direction I am going beyond the allowable or might facing a non-convergence error. Please clarify whether is it okay without giving Mu for -Y direction with zero gap?

Friction on -Y restraints? Check your output. If you see a large +Y load on any of those -Y restraints, friction may reduce lateral response. If you have small +Y loads, then including friction will have little effect - on this model.