In the attached example, 3 methods are presented for a base excitation in a harmonic analysis – The Large Mass method: used for several years, the acceleration is replaced by a force applied to a large mass fixed to the base of the model. This mass is a lot heavier than the total mass of the structure (>10^3). To replace the A0 acceleration, an equivalent force F = ML*A0 is applied. – The Enforced Motion method: available since R13 for MSUP harmonic. This method create a loadvector in the modal basis which allow to apply an acceleration or a displacement – The Full harmonic method: more accurate but also more time consuming. The displacement (or the acceleration) is directly applied threw an imposed displacement (using D command) Nota : In harmonic, displacement and acceleration are linked by the following equation : A = w².U (w is the pulsation)

Attachments:
1. 2040083.pdf
2. 2040083.zip