The frontal solution method in LUSAS uses a Gaussian reduction technique to solve the finite element equations. This technique requires that the structure stiffness matrix is non-singular and means that the structure or any components of the structure must not permit any rigid body displacements or rotations. Failure to comply with this criterion will result in a zero pivot message.

Although the new multi-frontal solution method is able to automatically apply corrections in the presence of singular matrices and provide a solution, the results will be seriously in error nevertheless.

Because zero pivots are generated through poor conditioning as a result of modelling errors, it is recommended that use is made of the checklist provided that give a list of the more frequent causes and their remedies.