VIBRATION DESIGN
VIBRATION DESIGN
(OP)
i was doing some research and found a artile stating that vibration design criteria only needed to be checked for idealized framing layout. This is a far different approach then what i have taken in previous projects where vibration designs were heavily dependent on deflection. I wanted to get some opinions on this approach.
Thanks, see link below for article.
https://communities.bentley.com/products/structura...
Thanks, see link below for article.
https://communities.bentley.com/products/structura...






RE: VIBRATION DESIGN
RE: VIBRATION DESIGN
RE: VIBRATION DESIGN
I may be able to offer some "historical" insight about why the article was written and what they were trying to accomplish with it. Granted, this is total speculation on my part. But, I feel confident in my speculation.
My guess is that this article was written in response to criticism that a competing program (my company's RISAFloor) was throwing their way about the limitations of their DG-11 implementation. Specifically their inability to perform any calculations for bays "irregular" framing. They want to paint what we (and their users) were seeing as one of RAM's weaknesses into a strength. That way they could reduce the number of their users who were ditching RAM in favor of RISAFloor. As such, my belief is that this is article was written with a dual goal.... marketing and technical.
Now, there is some truth to what they say in that article. So, don't completely discount what is said. They make some valid technical points. It's just that those points should be that this weakness of RAM's is not as severe as it first appears. Not that it should be viewed as a "strength" of their program. Really, that's a pretty transparent indicator of the article veers away from the technical goal in order to achieve its marketing objectives.
My company had been hammering them pretty hard on their weaknesses related to "irregular" framing. So, I understand their desire to combat the narrative we were putting out. And, after having discussed the subject with Dr. Murray I understand where they were coming from with their implementation.
Note:
There was a previous Eng-Tips discussion between me and Dr. Murray on the subject of irregular bays and floor vibration. Eventually, we came to the conclusion that RAM's exclusion of irregular bays was NOT necessarily appropriate. And, that the procedures of Design Guide 11 can and should be used to determine vibration or frequency problems in irregular bays.
Specifically, we discussed the example shown in Design Guide 11 figure 7.2. Where the "irregular" bays in a floor system exhibited the most severe vibrational response on the floor level. Enough to warrant adding in additional columns to change the frequency of the irregular framing. This is a case where RAM's limitation would have ignored a bay because of "irregular" framing but where RISAfloor would have identified a vibration problem.
RE: VIBRATION DESIGN
I looking for a quicker approach then DG 11 approach for irregular framing and talk to some engineers that just up the deflection criteria to L/600 which seems to be very conservative with some of the previous example I compared it too.
RE: VIBRATION DESIGN
Sensitive equipment is a different animal. A lot of the underlying concepts are the same. Especially as far as calculating frequency of the floor system or beam or such. But, the acceptability criteria is quite different. Chapter 6 of the design guide rather than chapter 4 or 5.
The only experience I have with sensitive equipment equipment is from being in the cube next door to an engineer working on some support framing for an MRI. I absorbed some knowledge through osmosis. But, not enough to give you any real quality advice.
RE: VIBRATION DESIGN
Use the software to identify the critical areas only, but then perform your own numbers to justify your design. Why wouldn't you when the success of your floor system is wholly dependent on the performance of its vibration and stiffness.
Let's not be lazy and trust the computer.. you will usually get best results when you do the thinking, as it appears you have done here.
RE: VIBRATION DESIGN