Response spectrum 1

[mech2926]

Hi,
I have a question on response spectra. I have attached a figure showing an arbitrary response spectrum. Assume that my component's first mode is at the vertical red line. If I assume that all the mass is participating in that mode, and apply the acceleration (in my Nastran model) shown by the horizontal red line, is that conservative?

My thinking is that regardless of what other modes the item has, it should never see an acceleration higher than the horizontal red line. But I'm not completely sure and would really like someone to either confirm this or tell me I'm wrong.

Thanks!

 

[hacksaw]

agreed, it is also not uncommon for fluid turbulence spectra, that is why the original query is puzzling is stating (as i read it) that given spectra is that of the "response"

 

[TERIO]

It is of the response. Each frequency - acceleration point on the curve the it the peak response of an SDOF oscillator, with frequency f, exited by the given input motion at its base.

 

[hacksaw]

then if the peak in the originally posted "response" is that of a SDOF oscillator, what is the meaning of the natural frequency indicated the original post?

 

[TERIO]

It is not just the peak response of one SDOF oscillator. It is the peak response of many SDOF oscillators to the same input. See attached sketch.

 

[electricpete]

Here is a discussion of the term "response spectrum" in the same sense that Terio is using it.

http://en.wikipedia.org/wiki/Response_spectrum

I agree the term seems a little misleading if you haven't heard it used that way. It's not just spectrum of response of a given system to a given input. It's a spectrum of responses of multiple sdof systems to a given input.

=====================================
(2B)+(2B)' ?

 

[electricpete]

Correction/Calrification:

It's not just spectrum of response of a given system to a given input. It's a spectrum of responses of multiple sdof systems to a given input.

should've been:

It's not just spectrum of response of a given system to a given input. It's is based on response of a spectrum of sdof systems to a given input.

=====================================
(2B)+(2B)' ?

 

[electricpete]

to hacksaw - I apologize if you are already familiar with the terminology I mentioned. I cannot answer your question about original post... haven't followed this thread close enough to understand it or make any claims about what he meant.

=====================================
(2B)+(2B)' ?

 

[hacksaw]

its all in fun no harm taken, just like to see the queries pinned down to the extent possible, and who knows maybe i'll learn something, eventually...