concrete damage plasticty

Hi

is there a way to get the characteristic length of one element? I wanna calculate xult (when the element is cracked, fracutred..).

I use the concrete damage plasticity model and after reaching the tensile strength i assume a linear softening with fracture energy.

Input are:

Young´s modulus

max. tensile strength

fracture energy

Outpu:

when do i reach xult or what is the plastic strain equivalent