Internal General beam Element

disla

Hello,

I’m comparing the input values required in the Internal General beam Element and the ccx 3D Timoshenko beam element U1.

Ccx is using an advanced coded version of Timoshenko Beam Element (U1/B3D2) [109]
That implementation has implicit that the beam cross-section is symmetrical, or the element local coordinate axes are selected to pass through the cross-section shear center.
Timoshenko shear coefficient accounts for the different shapes of beam cross-sections. (I assume I11 and I22 should then be given with respect to the shear center).

Ccx general beam is defined by I11, I12 ,I22, A, k (Timoshenko shear coefficient)

¿What about the internal general beam element?

Internal general beam is defined by I11, I22, A, J (Torsion constant) and Perimeter
¿Is it the same formulation but just written in terms of J ?. ¿Is the general section limited to symmetrical cross sections?
¿Are you assuming rectangular cross section as shown in the GUI picture?


Thanks in advance.

[109] Yunhua, Luo, An Efficient 3D Timoshenko Beam Element with Consistent Shape Functions. Adv. Theor. Appl. Mech. 1 , no. 3, 95-106 (2008).

Victor

The internal solver's beams assume shear center = centroid, so they're not really correct for asymmetric sections. The general section doesn't necessarily correspond to any rectangle though because you can define I and A in a way that isn't a rectangle.

Perimeter is only used for some kinds of load and isn't part of the stiffness.

disla

Thank you Victor.