Vibrating wood floor system

[rheim]

A prospective client has a floor system (2x10" lumber @ 16" o.c., joist span 12 ft) that is vibrating (vertically) frequently and for hours at a time. The source of the vibrations is unknown. He had somebody measuring the frequency, but they couldn't tell what caused the vibrations.
While there are analytical methods for steel joist floor systems, I didn't find something similar for wooden floors.

Does anyone have an idea how to dampen/mitigate the vibrations?
A common sense approach rather than analytical?

Any input is appreciated.

 

[SWComposites]

turn the stereo down at notch or two ?

is the house in one of those "mystery spots" along popular tourist routes ?

is there well drilling going on nearby ?

add some weight to the floor ?

 

[CTW]

Is this a residential or commercial building?

I would suggest trying to locate the source of the vibration before blindly trying to solve the problem.

 

[ishvaaag]

I second CTW, sound, thumps, roars, murmurs, visible movements and activity at reasonable proximity of the site may guide you to proper adjudication of the origin.

Use resonance as a guide of the origin, when come to your floor, the vibration comes near the frequency that was made to be investigated, so movements at this frequency should be given priority as likely source.

 

[csd72]

rheim,

The atc put out a guidance note on timber vibration though I am not sure how helpful it would be.

The fundamental are still the same for all materials so I suggest that you research vibration in general to get a handle on things.

Modern research has shown that the key is usually the level of damping and the fact that this continues for several minutes indicates to me that this is likely a large factor.

The worst thing you can do is recommend a solution that does not fix the problem so make sure you understand the cause before trying a generic solution.

 

[MiketheEngineer]

That is weird esp since the 2x10's are only 12' long. Some outside source is causing the problem - I would think. But you might check the HVAC or plumbing for vibration sources.

You might try blocking between a couple of joists to see if that helps - might - might not.

 

[EngineerTex]

What's the frequency?

Remember that if you add weight, it will not dampen the system, it will only change the frequency (lower).

If the problem is from rotating machinery, as suggested by Mike, adding weight may or may not solve the problem. There may be a number of excitation sources and if you add weight and happen to resonate with one of these other frequencies, you could end up making the amplitude (and stresses) much higher. I don't have lots of experience with wood structures, but I think that would be a problem.

As for sources, I'm more inclined to go with something going on inside the building, as suggested above, but to throw out a wild postulation -- how about vortex shedding off of some horizontal portion of the building due to sustained winds? The roof, maybe? Is this located anywhere between Amarillo and Fargo?

Engineering is not the science behind building. It is the science behind not building.

 

[zcp]

Check out 'Machinery Vibration' by Wowk. Excellent checklist for discovering and then finding a remedy for issues like this.

ZCP

http://www.phoenix-engineer.com

 

[msquared48]

Any tunneling going on in the area?

Mike McCann
MMC Engineering