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Re: Vibrating machine

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Dear Ritesh,
 
If you do have access to GTSTRUDL software then please note that Pseudo dynamic force ( Equivalent static force ) can be calculated for different dynamic loadings on vibrating foundations.
The same may be combined with the other static loadings for Static analysis. Also, note that the Pseudo dynamic force is based on the max. global displacements at each joint at any time, hence the static equilibrium may not be achieved.
 
Regards,
 
Bhavin Shah
 

 
On 1/9/06, ASC <ggg(--nospam--at)bigpond.net.au> wrote:
Question by Ritesh:
 
Hi all,
  
  I have checked that natural frequencies of foundation and of machine are apart by atleast 20 percent. Also, amplitudes have been checked against permissible amplitudes by using Barkan's method.
  
  However, for static analysis of Machine foundations, how the amplification in the dynamic force can be considered with respect to natural frequencies of the foundation and excitation frequencies of the machine.
  
  Please help.
  
  Thanks in advance,
  
  Ritesh
 
REPLY:
 
Assume the machine to be at resonance.
Get the damping ratio. (Site dependent)
Use single-deg-of-freedom formula to get magnification.
Multiply the unbalace force by that magnification.
 
Sincerely,
Gregory from Oz