1/2D element like membrane, plate, truss?

[ebrahim raeyat]

I know we have ElementGeometry1D that give a section type and typical rect, circle, pipe. ElementGeometry2D for shell element.
my question is: how can i define membrane, plate , truss and etc. I don't mean editing .ini file for calculix, i mean in general. thanks

[bernd]

I know we have ElementGeometry1D that give a section type and typical rect, circle, pipe. ElementGeometry2D for shell element.
my question is: how can i define membrane, plate , truss and etc. I don't mean editing .ini file for calculix, i mean in general. thanks

If you mean in general by the FreeCAD FEM GUI than the answer is no it is not possible ATM. We would need some objects to define these attributes and than the ccx writer would need to be adapted in this regard.

bernd

[ebrahim raeyat]

If you mean in general by the FreeCAD FEM GUI than the answer is no it is not possible ATM. We would need some objects to define these attributes and than the ccx writer would need to be adapted in this regard.

bernd

thanks. yes, and another thing:

define section? I mean another object that can assign to element. for example assign section to truss or beam element.

[ebrahim raeyat]

opensees has complete element library for structural engineers.

OpenSees commands

can i develop some of them in FreeCAD? specially Beam-column, truss and membrane element? thanks.

for can, i mean ability?!

[bernd]

ccx has a lot of elements too http://web.mit.edu/calculix_v2.7/Calcul ... ode25.html

ATM in FreeCAD FEM there is no object to choose the elment type. If you mesh a mesh with 8-nodes brick, an 8-nodes brick is used in ccx. If you mesh with a prisma element a prisma element is used in ccx.

As an example. If the mesh is made with 2 node line elements in ccx a 2-node beam element is used. To use a 2-node truss element one would need to edit the input file. Same for shell elements ATM we can not distinguish between shell, plate or membrane 2D element.

For this a new object would be needed to quantify the element type. The difficaulty in an element chooser is to stay solver independent as we do with all FEM objects. The elementlibraries are quite different in different solvers. We could give it a shot and start.

I would not mix this with the OpenSees solver implementation. As said this object shuld be solver independent.

For example oofem has a wide range of elements too, but in FreeCAD only quat4, tetra4 and tetra10 are supported ATM: https://github.com/berndhahnebach/FreeC ... #L163-L184

To get started with the OpenSees you would only need one element type, your favourite one, or the one you have some examples to test with. All other element types could be added later on if the solver works.

[ebrahim raeyat]

ccx has a lot of elements too http://web.mit.edu/calculix_v2.7/Calcul ... ode25.html

ATM in FreeCAD FEM there is no object to choose the elment type. If you mesh a mesh with 8-nodes brick, an 8-nodes brick is used in ccx. If you mesh with a prisma element a prisma element is used in ccx.

As an example. If the mesh is made with 2 node line elements in ccx a 2-node beam element is used. To use a 2-node truss element one would need to edit the input file. Same for shell elements ATM we can not distinguish between shell, plate or membrane 2D element.

For this a new object would be needed to quantify the element type. The difficaulty in an element chooser is to stay solver independent as we do with all FEM objects. The elementlibraries are quite different in different solvers. We could give it a shot and start.

I would not mix this with the OpenSees solver implementation. As said this object shuld be solver independent.

For example oofem has a wide range of elements too, but in FreeCAD only quat4, tetra4 and tetra10 are supported ATM: https://github.com/berndhahnebach/FreeC ... #L163-L184

To get started with the OpenSees you would only need one element type, your favourite one, or the one you have some examples to test with. All other element types could be added later on if the solver works.

it is true, but i think we can add some property to element to distinguish different element type for every solver. beside that many elements are common in all solvers like beam, truss, shell, membrane, plate and so on.

[ebrahim raeyat]

thanks @bernd. i want to analyse frame structures, like portal frame. but i don't know how can i mesh this portal frame that it would be only contain 4 nodes and 3 beam-column elements. i think it is very necessary for civil engineering.

portal.png (2.4 KiB) Viewed 1203 times

portal.FCStd

(30.79 KiB) Downloaded 25 times

[bernd]

4 nodes means first order elements without middle node ...

- set gmsh mesh object attribute ElementOrder to 1st
- use min element size 5000 mm

portal_meshed.FCStd

(19 KiB) Downloaded 29 times

Screenshot_20200329_173253.png (57.26 KiB) Viewed 1184 times

[ebrahim raeyat]

Thanks @bernd, I know it, but i mean in general. when i have 2D also element with 1D in one model.

[bernd]

Thanks @bernd, I know it, but i mean in general. when i have 2D also element with 1D in one model.

I do not really understand the question? Would you post an simple example?