Hi Hugh
It seems to me that all your examples can be described using an acceleration. You can define this using a gravity load (heave), or a centrifugal load (pitch/ roll). you will have to find a way to constrain your structure though. You can use the location where the vessel is mounted to the thing that supports the vessel (a ship?).
Although: pitching 8 degrees in 5 seconds is a velocity, that in itself will not cause a stress (it's a constant motion) it's the acceleration that does it.
does this help?
Erik
