Dear Peter, thanks for the valuable information on your method. I wish I knew about this approach earlier!
Eventhough as you mention, the range of Poisson's ratio in some lattice models can be close to concrete-like material when using a lattice network, the following concerns remain:
1. Inaccurate internal stresses in the body due to the nature of the lattice network and the inability to incorporate Hooke's law. For example horizontal struts fall in tension in a vertically applied uniaxial compression.
figure adapted from Asahina et al. (2015)
It is shown that it can be fixed by some methods incorporating the Poisson effect (Asahina et al. (2015))
2. When it comes to mesoscopic modeling of the bodies with different PR values, such as steel, aggregates with different PR than the matrix or rubber inside the concrete, etc. (most lattice models can't be combined with FEM element like your approach does)
3. Some methods that fix the PR issue in lattice-like models have other side effects.
May I know if your method of coupled CST and Truss elements can fix the issue 1 above?