• Registered: 2011-01-04
  • Posts: 16

Topic: Integration points

I was not able to determine the number of integration points actually used for the finite elements in my 2D modelling.

In the definition of the macro-elements I have used the mixed procedure, which generated mixed shapes, as expected.

In the Theory manual I found a good description of the theoretical properties of the CCIsoQuad element (full or reduced integration). I have searched the input file for the full denomination of the macroelements used (CCIsoQuad <xx>) but I was not able to determine it.

Can I get a hint where to look for it?

Thank you in advance,
Cosmin DAESCU

Quote Post 1

  • dpryl
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  • Registered: 2007-07-13
  • Posts: 1,107

Re: Integration points

I am not sure if I understand your question. I assume you are using ATENA Engineering 2D. If you are interested in all the integration points, why do you simply not output their coordinates (or stresses or whatever in them) from the Postprocessor?

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Quote Post 2

  • Registered: 2011-01-04
  • Posts: 16

Re: Integration points

Maybe I was not expressing correctly.

I want to write an article and I am supposed to give some details about the integration scheme. I am not sure if Atena is using (for my model) a 2x2 or a 3x3 integration scheme.

Thank you,

Quote Post 3

  • dpryl
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Re: Integration points

The Theory Manual is the right place to look, above all chapter 3.3 Plane Quadrilateral Elements: These are isoparametric elements integrated by Gauss integration at 4 or 9 integration points for the case of bilinear or bi-quadratic interpolation.

Linear elements: 4 integration points, bilinear interpolation, quadratic elements: 9 IPs, biquadratic interpolation.

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Quote Post 4

  • Registered: 2011-01-04
  • Posts: 16

Re: Integration points

Thank you.

I've read the Theory manual. And in the subchapter 3.3. it is stated exactly as you mentioned. So, in order to see if I got it right> If I use Atena2D and a mix of triangular and quadratic (surface) elements, the integration scheme for the triangular elements will have 6 integration points, while for the quadrilateral elements it will have 9 integration points?

In fig. 3.10 in the theory manual, is presented a figure about these integration schemes. As far as I can understand, the reduced integration scheme uses 2x2 integration points, while the full integration uses 3x3 IPs. I am not sure how can I know if my model uses a reduced or a full integration scheme. I assume it is a full integration scheme, but I still need you to confirm it for me.

Thank you in advance,
Cosmin

Quote Post 5

  • dpryl
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Re: Integration points

I see it is easy to mix the approximatioon degrere (linear or quadratic) and the shape (triangle or quad)...
If we concetrate on the quad elements only, those with linear approximation have 2x2 integration points, and those with quadratic approximation have 3x3 integration points. Reduced (degenerated) elements can be derived from both of them (and are used for special elements and special cases where some of the DoFs do not exist). Therefore, you only need to check the element degree for your macroelements to know if you have linear or quadratic quad elements. .

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Quote Post 6