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Car Shredder Fdn

Car Shredder Fdn

Car Shredder Fdn

(OP)
I am designing a pile foundation to support a car shredder mill.  The manufacturer gave dynamic forces and frequencies on the drawings, so I have performed a time history/dynamic analysis in staad to get the foundation natural frequencies and vibration response.

The natural frequency of the foudation is 50% removed from the machine, so I am good there.  But the vibration amplitudes are higher than I would expect.  The nature of the mill is that it is constantly changing the dynamic load based on how big/dense/fast the scrap is coming in.  

Has anyone designed one of these, and what guidelines did you use for permissable vibrations?

Thanks.

RE: Car Shredder Fdn

Do you mean 50% higher than operating frequenci(ies)?
Waht allowance have you made for damping from surrounding soil?

RE: Car Shredder Fdn

(OP)
50% higher in the vertical and 50% lower in the horizontal than the operating frequency (10 HZ).  Can't seem to get enough stiffness to get 50% higher in the horizontal.  Using 5% damping right now, that seems low though, 10 or 20% may be more appropriate I am looking into that.

I am not yet sure that having the vertical natural frequency above and the horizontal below is good practice- it seems like in some direction between the vertical and horizontal the frequncy would match the machine.    

 

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