I want to know regarding the evaluation stress for Hydrotest (HYP case in CII).
I have entered a pressure value for hydro test in my model (Use the Code B31.3), but I find the Allowable stress is 0 on the Stress report. There is a note: NO CODE STRESS CHECK PROCESSED.
I checked the material database, and then, I find the Yield Stress of CII’s material are all blank. I was only to input Yield Stress value of the material (A106 B) used in my current model which lie on the material’s auxiliary area. This time I got my anticipant result.

Now, I have three question about that.
a.Is it a right operating way for what I have done? If yes, I think it is convenient for user if CII’s material database added Yield Stress values.
b.How to evaluation Hydrotest (HYP case) in CII? I have not find it in the code B31.3. It’s seems implied in Para.345.2.1(a).
in CII’s Stress report, I find it is slightly differ from what I have entered Sy value. i.e. my value is 300000KPa, but CII’s “Allowable Stress” is 299999.5KPa. Why? Of course, this is effect nothing.
c.What is the principle or formula for CII calculate the Code stress of Hydrotest case? Is it the same as “SUS” (Except differ from the density between water and fluid, and ignored Spring hanger H replaced by Rigid Y restraint)?

Thanks!

Thomas Lee

a) Yes. Sy (yield) values have been added to the database. What version of CAESAR II are you running?

b.1) True, B31.3 doesn't explicitly give you an equation for this. CAESAR II uses 90% of yield as the allowable.

b.2) Computers can't represent floating point (real) numbers exactly. This is why you see this difference.

c) Yes.

Thank you for your answer!
Now I am still doubtful for your answers:

a)I’m running version of CII is 5.0. I checked again and find that Many of Codes (i.e B31.3) have not the Yield Stress values in the material database except some Code such as B31.4, B31.8,etc. They are maybe exist in the Version 5.1 if your said is right, I guess.
b.1) I find it is not as same as what you said CII uses 90% of yield as the allowable. But it uses 100% of yield as the allowable. You can try it.

Thanks!

Thomas Lee

B31.1 uses 0.9*Sy, B31.3 uses 1.0*Sy. Good practice to use 0.9*Sy.