Gravity should be OK though. You also have to add the stress stiffening under Loads & Constraints which triggers a *STATIC step to obtain stress which is used for a subsequent *FREQUENCY step.
Custom step contents adds things to the *STATIC step, not the *FREQUENCY step, which I don't think is supposed to have any loads. Without stress stiffening, there's no *STATIC step to put the loads in.
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Gravity should be OK though. You also have to add the stress stiffening under Loads & Constraints which triggers a *STATIC step to obtain stress which is used for a subsequent *FREQUENCY step.
Custom step contents adds things to the *STATIC step, not the *FREQUENCY step, which I don't think is supposed to have any loads. Without stress stiffening, there's no *STATIC step to put the loads in.
PS Gravity could be applied for example to calculate period of body like a physical pendulum
Excuse...the right one attached