4. Summary of results

• To obtain a good precision of the results, it is first necessary to obtain a precise and perfectly orthogonal modal base (CALC_MODES):

	by avoiding multiple modes (different stiffness on the unexcited degrees of freedom),
	by correctly calculating rigid body modes (prefer the option “CENTRE” in CALC_MODES to the other options),
	by specifying the method “JACOBI” (in the keyword factor SOLVEUR_MODAL) for a complete modal extraction.

• The accuracy of the results is good both for travel and for speeds and accelerations.

For the elastic response of the system (relative displacements \({u}_{3}-{u}_{1}\)), the numerical precision is slightly lower due to the numerical accumulation of errors on the absolute values.