All constraint equations are based on small-rotation theory. Their use in large-rotation analyses (NLGEOM) should therefore be restricted to cases where the directions of the degree of freedom included in constraint equations do not change significantly.

You can use the internal multipoint constraint (MPC) feature of certain contact elements (CONTA172, CONTA174, CONTA175, and CONTA177) in cases involving large rotation. For more information, see Multipoint Constraints and Assemblies in the Contact Technology Guide.

The presence of constraint equations can produce unexpected reaction and nodal force results. For a related discussion, see The General Postprocessor (POST1).

The constant terms in the constraint equations are considered to be boundary conditions. Therefore, they result in harmonically varying loads when included in a harmonic analysis.