Natural Frequency

Dear All,

I did a dynamic analysis and the lowest frequency i got was 4.54Hz at T1=232C.
Now, when I change the temperature to T1=191C the frequency is 4.85Hz.
Then I again change the temperature to T1=330C and the frequency is 4.5Hz.
I then went lower to T1=175C and the frequency is 4.85Hz.

No other parameters was changed, only the temperature.

The question is does the change in temperature affects the frequency experienced by the piping system? If it does, is there equation or formula that can justify?

I have been searching for the answer for this for a long time now and had little to no result.

Regards,
Bryan

It could have to do with your "static load case for non-linear restraints" choice; if you have chosen the OPE case, supports might have different behaviour in different temperatures.

Either that or Young's Modulus

We've found it Dave...The support is lifting off in the hotter temp. while sitting in the lower temperature, thus the difference in the modal characteristics of the system...

Dave, your reply to this post raised a question to me:

- Does CII pick the relevant E based on the "static load case for non-linear restraints" setting? if not, could you explain where to set it up?

a

In dynamic analysis, CAESAR II will use the elastic modulus used for the static load case defined as the "static load case for non-linear restraints"