Why CII 2014 always shows SIF/Index In Plane (Out Plane) equal to 1.0 in case of FRP Bend in stress report??

However, when I select Miscellaneous Data, it will show a range 1.0 --> 2.5 ??

Hello,

Could anyone advice?

Thank you

Van Ha

Please check the code used for FRP Stress analysis.
Also the setting in .cfg file for "Allow User's SIF at Bend"

Most of the code calculates FRP Fittings SIFs from Figures 7.1,7.12 of BS7159. Better to double check SIFs before used for analysis as there is complexity of the an-isotropic material properties.

I hope it helps.


Regards,
Mahesh

I find out that this problem comes from the thin wall thickness condition D/t>100 (as per ASME B31.3), the k and i on elbow/bend will be effected by pressure. Miscellaneous Data report will give a range of i and k from zero pressure to full pressure. However, that's for steel pipe by using ASME B31.3

In FRP case, there is warning D/t>100. I guess that the software will applied same philosophy as for steel pipe. But the presure effect on large diameter of FRP D/t>100 seems has not been specified in the code B7159 or ISO14692 (please correct if I wrong). I realize that CII use SIF value 1.0 for elbow/bend in this case. ISO14692 limit SIF for elbow/bend up to 2.5, but we cannot define sif for elbow/bend directly if I want the conservative calculated stress (sif=2.5)

Any comment is appreciate.

Have you tried Mahesh67's suggestion: allowing CAESAR II to use a user-defined SIF by setting a configuration switch?

I tried, and I see there is nothing change in Classical Input when I select Bend option on my working element.

There are still "Radius" & "Type" & "Angle 1,2,3" & "Node 1,2,3" & "Milter Points" & "Fitting Thk" & "K-Factor". There is no any field to input SIF directly for Bend.

Looking for advice.

The SIFs are defined on their own Auxiliary Data set, not the Bend definition.

Hi Dave,

Could please you tell me (by snapshot) where the Auxiliary Data set is? Since I have never tried to define SIF for bend before.

Thank you.

Here:

Hi Dave,

If I'm getting Ki, Ko from FEBEND program. Which Ki or Ko should I input? Since I see that there is only one location of inputting K-factor at bend option.

Any advice is appreciate !

CAESAR II uses a single k in the bend stiffness matrix.

But there is Ki and Ko from FEBEND, which K shall be input in CII?

For flexibility analysis I would suggest the smaller of the two as that would create a stiffer bend which would probably be conservative in strain loading.
What are the two values?

Input data: OD=762mm, Bend thickness = 5.72mm, Bend radius = 1143mm

Ouput report for Flexibility from FEBEND as follows:

BEND FLEXIBILTIY FACTORS:

Shell finite element flexibility factors printed below
consider the effect of the attached pipe, and the optional
welded staunchion. Ki, Ko values printed should be entered
directly into a beam type pipe stress program. The CODE
Ki, Ko factors were computed using h = (tR/r^2), and
K = 1.65 / h. Additional factors are for one and two ends
flanged respectively.

FE Computed Ki = 30.910
FE Computed Ko = 28.810
---------------------------------Single---Double
CODE Computed Ki = 36.087 21.579 12.904
CODE Computed Ko = 36.087 21.579 12.904


The values below are the ratios of the shell finite element
displacements to the corresponding beam-type displacements.
Loads were applied axially to the bend end, and torsionally
to the bend end. The flexibility factors for the beam type
analysis are those used in the piping codes. Ratios greater
than 100% indicate that the shell model is more flexible
than an equivalent beam model of the bend and attached
straight pipe.

Axial Displacement Ratio = 19.842 %

Torsional Rotation Ratio =1285.991 %