AISC DG 11 _ Sensitive Equipment 1

[theshearstud]

Does anybody know why DG 11_Sensitive Equipment uses peak velocity when checking floor vibrations while the majority of the related literature state that RMS is more appropriate?

 

[KootK]

Peak response strikes me as quite appropriate for equipment. While a human will perceive vibration in the context of it's variation with time (rms averaging), equipment will need to be able to accommodate instantaneous response peaks. A medical image, for example, is taken instantaneously and, perhaps, at the instant of peak response.

Does the other literature that you've reviewed elaborate on why RMS is more appropriate for equipment?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[theshearstud]

Your point makes sense. I could not find elaboration on why RMS is used. In the below doc. written by Ungar (who seems to be one of the top experts in this field), he uses RMS.

http://www.sandv.com/downloads/0709unga.pdf

 

[KootK]

Well, if you had to chose whether to trust me or Ungar... let's just say that I wouldn't be offended either way. A couple of other thoughts:

1) Many of the article sections that mention RMS are discussing operating rooms which, Imagine, is mostly about human (surgeon) perception.

2) Both the GE and Phillips sample criteria make reference to peak values.

3) Where there is a geometric relationship between RMS and peak values, the choice of which to use is really arbitrary as there will be a one to one relation ship between RMS and peak values. This is the case for DG11 procedures where we're assuming a sinusoidal distribution and RMS = Peak x SIN 45.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[theshearstud]

Appreciate the insight

 

[Hokie93]

Another source of insight would be to contact Dr. Tom Murray (principal author of AISC Design Guide 11). Dr. Murray can be contacted via the FloorVibe software website. Murray has promptly responded to my past inquiries.

I also saw a note just yesterday that AISC recently honored Dr. Brad Davis for his research work related to floor framing supporting sensitive equipment. Dr. Davis works at the University of Kentucky, Lexington and I assume his email address can be found through the university's website.

 

[theshearstud]

@Hokie93 - I'll give that a shot. Thanks.

 

[MrHershey]

I also had luck long ago contacting Dr. Hal Amick with basic questions. He publishes (or at least used to) quite a bit on this topic as well and seems to focus more on sensitive equipment.

His page on company website
Quite a few selected publications (free)

I would imagine it also has a lot to do with what the equipment manufacturers and the sensitive equipment industry want. Regardless of reasons or if they're right or wrong, if they have in their product literature that they need peak (not RMS) vibration under a certain level then that's your design criteria. If their equipment fails and structure exceeds the vibration in their product literature they're going to point the finger directly at you, right or wrong.