Pipe Stress Concentration Factor Modelling in ABAQUS

[subsealinepipe]

For pipe modeling I need to apply stress concentration in pipe model. In ANSYS the element Pipe20 allows stress concentration in the bending, however I do not know how to model stress concentration in ABAQUS (in ABAQUS i use Pipe21 or Pipe31 element). Kindly advise.

Regards,
Amir

 

[gurmeet2003]

To best of my knowledge, stress concentration is not modeled in FEA, but is a result of the analysis.

Gurmeet

Gurmeet
Time is an illusion. Now is the only thing there is.

 

[subsealinepipe]

Thanks Gurmeet, it depends how the modeling is done, what you said is generally correct provided that (i think) the modeling is near to reality and simplification is reduced, for instance in case a subsea pipeline (with concrete) is modeled by solid elements (not beam elements as is normal practice) the Stress Concentration Factor in the field joints (where the pipeline shall be welded and there is discontinuity on the stiffness) can be extracted from FEM. (For clarity, in case a simple beam with various cross sections is modeled in FEM using beam elements, the SCF which is calculated by FEM is far from the reality, because beam element is not suitable for this purpose and to get precise results solid elements provides better results.)
However, as a normal practice the pipeline is modeled by beam elements and the stiffness of concrete is usually ignored (ref to DNV-OS-F101 (Oct 2007) 5C207), and to count the SCF in the field joints it is manually calculated and then added to FEM. This has already been considered in OFFPIPE (FEM for subsea pipeline installation) and ANSYS (beam elements Pipe16 or Pipe20). However, I could not find the same in ABAQUS.

Regards,
Amir

 

[APipeliner]

In ANSYS and OFFPIPE, the software just multiply the provided SCF by the stress. It doesn't mean that your are calculating SCF. As you said, the best way to do that is using 3D elements. There is also another way which can give reasonable results with beam elements. to do that, define two section for your model, the first one with stiffness equal to pipe steel+concrete (you can use the mentioned DNV for calculating CSF) the second section just the pipe steel (for modeling the field joint).

 

[gurmeet2003]

Thanks for clarifying. I guess the problem was outside my realm of experience.

Gurmeet

Gurmeet
Time is an illusion. Now is the only thing there is.

 

[williwang]

Thanks for all...

Forever Young.....