Any beam failure criteria considering Nx, My, Mz, Mt, Vy and Vz?

Grasshopper Karamba3D
#1

Dear experts,

Von Mises stress (Sv) is a good failure hypothesis for isotropic materials like metals. Accordingly, the structural member fails when the applied stress (Sa) is higher than Sv.

How do I retrieve Von Mises stress from Beam elements?

I´ve only found that BeamView and Utilization components are the ones that produce stress results. However, BeamView only provides Axial Stress and Utilization only gives the maximum axial normal stress in the most external fibers. Furthermore, the Utilizations output from Utilization component are always calculated according to EC3 (EN 1993-1-1), and thus, they´re only valid for structural steels.

Am I right?

How would I consider the axial forces (Nx), torques (My, Mz and Mt) and shear forces (Vy and Vz) to decide whether some beam will fail or not?

Here you have an example to play with: MyBeamTest2.gh (96.2 KB)

Thanks!

PS: Here you have an interesting video about both ductile and brittle failure theories Understanding Failure Theories (Tresca, von Mises etc...) - YouTube (in minute 12 it is evidenced how well Von Mises criteria fits experimental data).

#2

Dear @Vigardo,
if you want to retrieve the Von Mises stress for a beam element currently (version 1.3.3 and 2.3.0 WIP) the only possibility is that you do it in a script which takes the cross section forces as input and calculates the cross section stresses based on these.
If you set the buckling length of the beam and truss elements to zero the EC3 procedure reduces to a design based on stresses and strength.
– Clemens