Hello,

In Caesar, i have seen , that you can change the in-plane SIF and out-plan SIF . But i have my dude about how to change the torsional and axial SIF.
In B31.3 (2010) said "St= It*Mt/(2Z), and It, In the absence of more applicable data , it is taken as 1.00".

But if i have this data (through another software), how i can introduce this data in Caesar?. Maybe this data is important in any occasions.


The same situation with Ia.

Thank you

Have a look at what the Code (B31.3 App D) requires.

It´s not a code issue, the question is how to introduce these index in Caesar when i have these data.

Besides, i´m not talking about the sif in plane and out plane, i´m talking about the torsional and axial index.

Technically you can't insert different values for torsional and bending SIF. As far as I remember, B31.3 does not intensify torsion. had you had another code like B31.1, you would have had to use only one SIF for all directions of the moment.

Pooria is correct, there is no SIF for torsion or axial stress in B31.3, that is why I wrote ..... have a look what the Code requires.

Caesar operates in accordance with the Code.

Sorry but is not true. ASME B31.3 (2010) in 320.2 Equation 23c-->
St = It*Mt/(2*Z),
It = index of torsion.--> In the absence of more applicable data , it is taken as 1.

But maybe i have more data , how can i change this value in Caesar?

Thanks

Dear David,

There's no way to input axial and torsional SIF in CAESAR II. But if you want to input user SIF and stiffness, you may use the following instruction in order to model realistic intersections:

1- Construct the intersection model using a rigid element from the centerline of header to the surface of the header where the branch pipe penetrates. See attachments. The end node of the branch element (41 in the example), should be different from the end node of the rigid element (40 in the example).
2- Insert the four calculated point stiffnesses from FE software in between the node at the end of the rigid element and at the end of the branch element.
3- Insert two rigid stiffnesses for the translational stiffnesses that are rigid in between the node at the end of the rigid element and at the end of the branch element.
4- Determine the in-plane and out-plane directions for the branch and insert the SIFs calculated by FE software. See example to know which direction is in-plane and which is out-plane for CAESAR.
5- Run FE software with the option to calculate the header (run) SIFs.
6- Insert the in-plane and out-plane SIFs from FE on each header element framing into the intersection. Also include a CAESAR II intersection type (that is, RFT, UFT, etc.) for the node. CAESAR will determine the correct orientation (even with the rigid element used for the branch – but this is only true for the header SIF orientations).

I hope this is useful.

Hi David,

You can also peform the calculation outside the Caesar. Say use the excel spreadsheet and input the torsional moments/sifs and axial forces/sif's and compare to code allowables.

Cheers!!!!!

In Version 6.10, there are two new fields on the "SIF Dialog", for "Ia" and "It".

Note, though, that Rich shows Ia & It rather that ia & it. In B31.3 I refers to the sustained stress index while i is the stress intensification factor used in expansion stress calculation.

Thanks so much Richard.