Topic: Finite element types in ATENA 2D


I am simulating an interface failure model using ATENA 2D for which I use quadrilateral elements and interface elements for my model. Is there a way to know whether the finite elements that I am using are linear or quadratic?

Codes for the respective elements are CCIsoQuad and CCIsoGap but no specific distinction between finite element type is given. Is this information provided in the manual somewhere? I checked the manual for GiD as well, in that number of nodes is specified in the code for example, IsoQuad<xxxx> for linear elements, IsoQuad<xxxxxxxx> for quadratic elements. However, I cannot find a clear distinction like this while using ATENA 2D.

Kindly guide me in this matter.

Re: Finite element types in ATENA 2D

Dear arjun.vithalkar, in ATENA Engineering 2D, you select the elements in the Macroelement dialog, section Properties (CCIsoQuad - linear, CCQ10 - quadratic, CCQ10Sbeta - quadratic, specifically developed for the SBETA material).

Is there any specific reason why you are interested in elements with quadratic shape functions?

We generally recommend to use linear elements for regions with expected strong nonlinearities like cracks. According to our experience, with cracks you get better results by refining to 1/2 element size than by switching to quadratic elements (while both use about the same memory and the quadratic mesh needs somewhat more CPU time).
You probably remember from some basic course on numerics or differential equations that the conditions for quadratic meshes to converge faster usually include smoothness of the solution of some degree, and this is typically violated for discontinuities like cracks. Therefore, it makes sense to use quadratic elements for elastic bending regions (typically, meshed with shells), but not for significantly cracked ones.