Hi there,
I am using the concrete damaged plasticity model and trying to understand the mesh sensitivity problem. In the documentation there is a definition for the characteristic length, which should reduce the mesh sensitivity: "Characteristic element length, which is a typical length of a line across an element for a first-order element; it is half of the same typical length for a second-order element."

I understand this geometric mean-based definition for first order elements: For beam or truss elements the characteristic length equals the element length and for two-dimensional elements it is the square root of the element area (cube root of element volume for three-dimensional elements). But what about the second-order elements? What does "half of the same typical length" mean? Because I thought - based on this definition - the characteristic length would then be the same for every integration point (just as in the first-order case), but when I print out the characteristic length for second order elements, each integration point has a different characteristic length. I think the characteristic length is somehow connected to the weight factors of the Gauss points, but I couldn't find any more explanation in the documentation.

Can anyone explain the definition for higher order elements/ where I can find it in the documentation or does anyone know, where I can find the publication on which the implemented definition was based?

Thanks in advance!