A fair comparison of beam results requires that all meshes, even the coarsest, be able to model the physics of bending. One layer of second-order elements can model bending stresses (and consequently bending stiffness) in a model of simple geometry such as the prismatic beam because those elements can model linear-stress distribution. If we instead used first-order elements, it would be impossible to model bending stiffness because firstorder elements can only model a constantstress distribution (across the beam thickness). Such an erroneous model would have produced gravely incorrect displacement results of 3.5 versus 13.65 mm.

It is important to note that one layer of second-order elements can model bending stiffness, which predominates in our beam. But experts recommend using at least two layers of second-order elements across members in bending for more complex shapes and when shear stiffness plays a bigger role in model behavior.