Greetings to All,
I had a doubt regarding Load case and Stress Check in Caesar

For stress check we consider following load cases.

(1)Sustained -Effect of weight and pressure (W+P1)
(2)pure exp.- Effect of only thermal expansion
(W+P1+T1 or T2-(W+P1))

In CAESAR, there is no case where we can check the stresses for the combined effect of thermal exp, weight and pressure, as actual when plant is in operating/desgn condition. Also I will like to know why we dont consider it for checking stress failure combined with expansion cases.

I think the thermal expansion combined with weight and pressure will increase the loads on various points (eg elbows, tee joint, etc) so there will be higher stresses at all these points.

So can we add new load case for stress check where we can combine with scalar addition the expansion load case and sustained load case.

Thanks..

Our learned and experienced mentors will advice u to read the appropriate codes first and then to use search function in this forum.

"So can we add new load case for stress check where we can combine with scalar addition the expansion load case and sustained load case?"

Yes, but what's the point? You would be calculating and displaying stresses for which no allowable stresses can be calculated, at least under the B31 family of Codes. Essentially, you would be checking for the case where your support spans were adequate at installed temperature but not at operating temperature. But if you have this potential failure mode, you are going to see considerable evidence of this in the Thermal load case, since CAESAR II is calculating the difference between the hot operating load case and the sustained load case and reporting that, as well as comparing it against the thermal allowables.

If your "hot operating" stresses are sufficient to cause a failure on the initial cycle, what do you think the fatigue load case is going to show? You can see for yourself quite easily; make up a simple model of a couple of spans with one end fixed and one end free. Choose the support spans so that the calculated peak stresses between at least one of the spans will cause a failure due to sustained loads in the hot operating load case. Check out the thermal load case report and then ask yourself your own question.

well said.... SAMAbdul

This question has been answered here on this forum many times. I notice you didn't specify which piping code you are referring to. Many codes do in fact perform a code stress check in the operating case, but B31.3 and B31.3 do not. However, B31.3 2004 provides optional Appendix P for performing an OPE code stress check. If you want to do this in Caesar II, go to Configure/Setup->SIFs and Stresses and turn on the option for Implement Appendix P and then re-run your analysis and you will have your OPE code stress check.

Good Morning Sir

I am thankful to all of you Sir,
Next time I will take more efforts befor posting a question.
thanks again