I am currently working on an offshore pipeline project which is based on dutch code nen 3650. I have to apply some load case factors on my loads cases manually and etc.
I compared the octahedral stress calculated by CII with the one I calculated by hand and surprisingly the results are far different. I wonder to know what causes such difference. besides, I would like to know what stresses are taken into account to calculate the "code stress" once the OPE has been chosen for a certain load case. is it dependant on the design code? my code is B31.1. I am fully aware of the fact that for EXP,OCC and SUS cases, the calculation of code stress is directly relevant to the design code.

regards

If the code design is NEN 3650 this don't have anything to do with B31.1.
The NEN 3650 section 10.5.6.b assessment criteria for the stress limit in accordance with the elastic theory is reflected by the following condition.
Sdesign / SCF < Slimit

Where: Sdesign = Calculated design stress - based on design loads.
SCF = Stress correction factor.
Slimit = Stress limit (allowable stress).
You need to check:
Equivalent Stress Sv1 (pm)
Equivalent Stress Sv2 (pm + pb)
Equivalent Stress Sv3 (pm + sm)
Equivalent Stress Sv4 (pm+pb+sm+sb)

As per NEN 3650, par. 10.5.6.b, the calculated stresses are to be combined into the so called equivalent stresses Sv1, Sv2, Sv3 and Sv4. The equivalent stresses for the different stress combinations are determined in acc. with table 9 of mentioned paragraph, and are checked against the stress limit Re(ө), taking into account the stress correction factor. This method considers a possible redistribution of stresses due to Elastic Shakedown (relaxation).

Loads case (just an example):
Sv1 pm 1.5 P1 compared against 1 x Re(Φ)
Sv1 pm 1.5 P1+ 1.5 W + H + 1.2 WAV +1.2WIN compared against 1 x Re(Φ)
Sv3 pm + sm 1.5 P1+ 1.25 T1 + 1.5 W + H + 1.2 WAV+1.2WIN compared against 1.5 x Re(Φ)

Just an example I offer , loads case depends by many factors and external loads. You have all description in standard.

Conclusion: Read the standard

Dear Marian,

thanks for your vast explanation, this is not the first time that I use NEN 3650 and I am well aware the standard besides, I can not agree with you on your example since for instance in SV3, the stress limit is 0.85(R+Rt)/SCF and not 1.5Rt ( it might be correct if the temperature was lower than 50C). anyways, apparently you have not done any NEN projects using CII otherwise you would know that we have to compare calculated stress by CII with NEN limits manually and of course you may choose a design code in order to run your file. B31.1 is the best choice in this regard since it considers rotation and bending all together (stoomwezen does the same too).
conclusion: read my question carefully

regards

Pooria
If you now this is ok, if you want to correct me is tke same ok, as I say this is just an example.
Regarding how may stress stress calculation I perform using NEN3650 I'm afraid to make a coment for you.

PS If you now how to make a stress calculation using NEN3650 why you ask such question?

Dear Marian,

I believe the purpose of such forum is that people could correct and help each other and not sarcastically give tips and conclusions.
my question is about the difference between octahedral stress calculated manually and the results derived from CII. I also would like to know how the code stress is calculated once the load case is set on OPE.

Regards
Pooria

The determination of the Octahedral Stress is detailed in the help text for the "Yield Criterion" (on the SIF&Stress dialog) of the Configuration Module.

For a B31.1 OPE load case, the "Code Stress" column is a basic mechanical stress calculation: F/A + Slp + Sb, where these terms are defined in the Quick Reference Guide.