I understand that the “Utilization Element” component in Karamba calculates utilization based on the Von Mises stress criterion and is designed according to Eurocode 3 (steel design).
How can this component be properly used or adapted for materials like concrete, which have very different failure criteria and are governed by Eurocode 2? Is there a recommended workflow or modification to correctly evaluate utilization for concrete elements in Karamba?
Currently (Karamba3D 3.1.x), no design routines are available that implement EC2. This feature is on our to-do list. As a workaround, we recommend using a linear elastic concrete material with reduced tensile strength and Young’s modulus to achieve realistic cross sections when applying a cross section optimization. At present, reinforcement design must be carried out outside of Karamba3D.
I would like to clarify the applicability of the Utilization of Elements component for materials with a brittle failure behavior.
According to the documentation, the component returns utilization values according to Eurocode 3, and for shells the ratio between the Von Mises stress and the yield stress is evaluated. However, for shell elements Karamba also allows the use of alternative failure criteria such as Rankine, Tresca and Tsai–Wu.
My material is a brittle material (e.g. compressed earth blocks / masonry-like material), for which the governing failure mechanism is tensile cracking and compressive crushing, and therefore a Rankine failure criterion is physically more appropriate than Von Mises.
My question is: Is it conceptually valid to use the Utilization of Elements component for shell elements together with the Rankine failure criterion to evaluate utilization for such brittle materials, even though the component is described as EC3-based?
In other words, should the shell utilization with Rankine be interpreted as a stress-based failure indicator rather than a code-based design check?
for shell elements, utilization is determined based on the selected failure hypothesis of the material. In Karamba3D 3.1, the EC3 procedure applies only to beams and truss elements. Therefore, using a material with a Rankine failure hypothesis should produce the desired results for shells.
If you’re uncertain, I recommend testing this on a small, simple example first.