Steady-state linear dynamic analysis 1

[rte4563]

I am running a dynamic analysis as described here:

https://classes.engineering.wustl.e...oks/stm/default.htm?startat=ch02s05ath30.html

I have a concrete foundation which has a turbine (left side) and a generator (right side) on it. The loads from turbine have vibrating forces at frequency = 150 Hz, and the generator 30 Hz. There has been done a similar exercise earlier with a steady state modal analysis in Abaqus, but there was only vibrating forces at one frequency and not two as it is now.

When I have vibrating forces at two frequencies, can I just do two separate steady state modal analysis? I need to make sure the vibration speed is under 3 mm/s. Can I take the vibration speed in each seperate analysis (at the same point in foundation) and simply add them to check if its under 3 mm/s? - like a linear superposition you would do in a linear system.

I have two set of loads like this; one set at 150 Hz and one set at 30 Hz.

 

[FEA way]

Two analyses and superposition of their results would be the way to go since this procedure is also linear.

 

[rte4563]

Thank you. I would then take the vibration speed at the same place on the foundation for one load at 150Hz another at 30Hz and then just add them?

If I wanna distribute the concentrated force P1 in the picture I posted, for example over 3 nodes, can I simply divide the load on 3 and and put it on those nodes? Similar to a static analysis how you can just divide the load without taking into consideration some dynamic stuff?

 

[FEA way]

Yes, it should work this way.

If you are using concentrated force load,its magnitude will be applied to each node.

 

[FEA way]

According to that engineering code (ISO 10816-3), it seems to be RMS velocity.