We failed. Or in fact I failed. We can not deliver solution which owner is willing to accept. He refuses adding concrete on top of the slab, equipment sales representative does not allow on using dampers, and I am unable to provide any other meaningful solution. Over an over again expectation is...
Gentlemen,
would appreciate you getting involved in a discussion on adding mass and a practical approach.
When analyzing a single floor, calculation shows that if I add 35psf all over (approx. 3" of concrete) to the existing floor, I will successfully reduce natural frequency slightly below...
@saplanti - thank you. This option was already discussed in our office, and we see such resistance for even providing dampers, that we know that isolating equipment on a separate structure would not work.
@Ideem - thank you very much for your post.
Gentlemen,
I went through all your suggestions, and although still do not have final results there are some noteworthy facts:
- I was able to receive the same frequencies for both floor and structure in other software. Roughly speaking numbers are/were ok,
- I changed approach. It is enough to...
human909 - I will try again to stiffen the floor, but somehow have got no success by now. Nevertheless will check again tomorrow.
On a site note, the article which you referred to. I have some minor academic experience (lat say less than 10 articles published), and would not argue with science...
human909: thank you very much.
Could you please
tell me what you mean by steel floors? Are those grating or something else? Since mine floor is concrete on steel deck (what I am quite used to in residential, but with shear studs) - do you classify it as steel or concrete?
The natural...
r13: fully agree, that it is difficult to find a good frequency which would satisfy each piece of equipment operating requirements. Here I am dealing with some units of 4-4.5HZ, and the previously one mentioned of 7-14HZ (owner's manual).
I really try to play back and forth with that. Just for...
human909: I do not remember providing Manufacturer of it, but you are definitely experienced.
As of right now it seems that if to my deck of 120mm (total), I will add 6-7" of concrete, I am able to reduce first frequency to 6HZ (in fact the 7th mode is the first above 7Hz). Still the structure...
@dauwerda - I kind of understand both approaches, but to do them concurrently? Adding stiffness will increase my natural frequency, whereas adding mass will decrease it at the same time.
saplanti - thank you very much. That is more or less what I am also doing (playing with additional bracing in floor plane and vertical), and really appreciate that Mechanical engineer joined this discussion. I have a huge respect in the subject of dynamic to mechanical (dont confuse with HVAC...
Pins at one end shall not worry you. Do not have good picture, but it is not cantilever, just short span supported (lightly) on precast concrete walls. This side is almost not loaded. Probably if removed from model, there will be no huge impact.
There is no composite action between deck and...
evo10: I noticed that operating frequency is 9.66HZ (580rpm), but still it comes through my natural one. Moreover if they ask for not having 7to12hz, I believe that it is wise to assume that equipment may operate in such range. As you noticed they just added plus minus 2.5HZ (or roughly 25%)...
evo10: in Autodesk Robot it is quite easy to do the whole building. Then I checked also locally whole floor (level). Then I checked single beam (using procedure from ArcelorMittal for composite decks/beams). No matter how I deal, I get values which are dangerously close to what the machine will...
r13 - that is a kind of idea I was looking for. Great piece of advice, and surely will check/start thinking of that approach.
If someone has any other experience/idea - would gladly listen to!
Natural frequency was calculated in Autodesk Robot, and was 8.91Hz. I also did some hand calc and got 8.73Hz. Even if I ommitted something, saying that it is around 8.5Hz sounds justified for me.
Equipment manufacturer cooperates very low with me, replying roughly: we deliver equipment, and you...
@SwinnyGG - went that way and got nothing ("You cannot have damper in between the machines base and the floor."). Situation is tough, and neither owner nor manufacturer understands why I am trying to cause problems.
Good morning,
I am looking for a piece of advise how to solve the issue when placing industrial equipment on an existing steel structure.
In details: 4sty existing steel frame (columns, beams + metal deck w/concrete) carries currently some flour mill equipment (old, mostly to be replaced)...
