Hello,

I am relatively new to CAESAR and stress analysis. I am doing system analysis(only pipe, doesnot include component analysis and pipe support analysis)using ASME B31.3.

I am confused about the load cases I have to comply with.I have been reading couple of books and this is the information I collected:

From
(a)Piping and Pipe Support Systems by Paul R Smith Pg75:-

(1)Stresses due to sustained loads Sl<Sh
(2)Stresses due to occasional loads(consider wind or siesmic+pressure+wt) <1.33Sh
(3)Stresses due to expansion loadings

(b)From ASME B31.3, 321 1st para "The design of support structures and of supporting elements shall be based on all CONCURRENTLY acting loads transmitted into such supports. These loads, defined in para 301, include weight effects, loads introduced by service pressures and temperatures, vibration, wind, earthquake, shock, and displacement strain."

(c)From ASME B31.3 examples, Appendix S301

(1) sustained load case for stresses - agrees with (a)(1) above
(2) Displacement load case for expansion stresses agrees with (a)(3) above
(3) operating load case for nozzle allowables(to aid in equipment design) and support forces & movements(to aid in support design)

They dont mention anything about (a) (2) above.

Does (a)(2) needs to be considered for allowable stresses to comply with code or not?

(c) CAESAR ii (correct me if I am wrong with this case)
When you enter all the input and go to 'Static Load case' screen and press Recommend button, it would show you all the load cases that necessarily need to be analyzed. I used this after entering ASME B31.3 as the code to be used and also entering wind and siesmic data. But, Recommended cases do not show that wind or siesmic have to be analyzed. They also dont show that I have to combine weight and pressure with wind or siesmic.

With the above, thinking logically I felt wind or siesmic have to be combined with pressure and weight and should be compared to allowables. So, I added a load case as occ in the project adding pressure+wt+siesmic. My pipe is failing with high stresses at a bend in this occasional load case. I am looking for causes and solution.

Meanwhile, please clarify if i am doing correct or not.

Thanks,
Deepthi

Hi there

Well done for reading the code and realising that the answers you are getting from Caesar do not make sense to you.

The recommended load cases given in CAESAR II are not the complete list of code required load cases.

You have to define your load cases using the load case editor and it is very important to define your loadcases correctly, otherwise your results may not be correct.

There is a tutoral on the coade website that shows how to set up the load cases under support/animated tutorials/static load case set up-modification. It would be worth your while to have a look at this next and see if this answers your query.

Thanks a lot for your response. I have gone through the animated Tutorial and it is extremely helpful.

I wish and request CAESAR personnel to compose more animated tutorials like this to understand and use CAESAR better.