[SMApp] Adding 3 noded straight and curved linear Timoshenko beams

[AlejandroCornejo]

📝 Description Finally, the time has come to merge the 3 noded straight and curved Timoshenko beams.

For this purspose I have added:

• Add virtual to some methods in the base 2-noded element to reuse a lot of code in the straight 3-noded beam
• Add the new straight 3 noded beam with 5th order polynomials and Hermitic shape functions to avoid shear locking. The element can use any beam constitutive law.
• Add the curved 3-noded Timoshenko element based on standard quadratic shape functions and reduced integration to avoid shear locking. This class is prepared to calculate straight cases too (the Frenet-Serret basis is not defined in straight beams, but in 2D can be sorted out easily).
• Add a complete test for the 2 added beam elements.
• The references for each implementation can be found in the .h files of each class.

Next steps: In future PR's I'll add the 3D 2-noded and 3-noded straight beams and the curved counterpart.

Glimpse of the behaviour in a thin beam clamped/nodal force case:

cr_linear_element result of a fine mesh of an arch:

and the result of one curved 3-noded Timoshenko element:

and with 4 elements:

[AlejandroCornejo]

@RiccardoRossi ping

[AlejandroCornejo]

any more comments?

[philbucher]

any more comments?

I would like to review again, but only if I manage today

If you have not heard from me by tmr then :+1: from my side

[AlejandroCornejo]

I added const to a few more methods and removed the unused method in the elemen utils :)

[AlejandroCornejo]

I think that now is ready @philbucher

[AlejandroCornejo]

ping