The resistance of the plastic material (ABS - acrylonitrile butadiene styrene) of Lego bricks far surpasses the force necessary to either join two of them together or break their unions. This makes it possible to conceive a model that ignores the resistance of the material and evaluates the stress forces over a group of bricks only at their union areas. If a Lego structure fails, it will generally do so at the joints, but the actual bricks will not be damaged.
This characteristic of bricks structures makes their discretization for modeling an obvious step. Instead of imposing an artificial mesh for simulation purposes only (as FEM does), these structures are already made of relatively large discrete units. A first simplification is thus to ignore the physical characteristics of the bricks and study only those of their unions.
Our second simplification is to ignore bending effects. In standard structural analysis, the effects of stress are observed as deformation of the original shape of a body. Here strain deformations are ignored altogether.