Reducing concrete floor vibrations 1

[Alan CA]

Hi everyone,

I have a suspended floor that appears to be very thin, so vibrations due to walking are annoying. Designing dampers for relatively small buildings could be expensive and the floor is office area and cannot be divided by walls. What other solutions could be contemplated to reduce the vibrations?
Had it been wood or steel flooring for example, adding blockings would have done the job, but concrete appears more complicated.

I'd appreciate your thoughts.
Rrgards.

 

[dik]

What is the construction? Concrete? Flat Slab or Flat Plate. What is the typical column spacing and slab properties?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[rowingengineer]

Carpet with triple underlay, as dik said we need more info.

 

[MIStructE_IRE]

Its unusual for a concrete floor to pass all other checks but fail in vibration. I’d be very interested to hear more about this one.

Is it pre/post tensioned? How thin? Span? Construction type? Etc.

Assuming you’ve checked strength. Does it pass deflection checks?

 

[Alan CA]

Thank you everyine for your input. I'm still collecting information about the slab, but regardless, I wanted to get your thoughts on how to reduce vibrations in flat concrete slabs in general.

 

[jayrod12]

Maybe a properly bonded overlay if possible? As far as I'm aware you improve vibration by adding damping (weight) or increasing stiffness.

So short of adding mass, the only other option is to increase the stiffness, which could be a multitude of options. Provide large diameter column capitals to shorten the spans. Provide beams between columns and then beams between beams.

Of course all of these have their own concerns, mostly negative moment capacity. But they are options.

 

[dik]

or increase damping significantly...

I've seen elastomeric composite damping material added (vibrations) as well as mass tuned dampers (seismic)... the latter is likely out of the scope. Can you add an anelastic isolater sandwiched between steel BAR and the concrete soffit. When I was a kid, I used to have an anelastic ball... was about the size of 'superballs' back then. With a superball, you could 'wind up' and throw it on a hard surface and it would bounce 20' or more in height... with the anelastic one, you could wind up and it would bounce maybe 2" or 3"... very high large hysteresis loop.


Found this:

https://www.princeton.edu/~maelabs/mae324/glos324/anelastic.htm

I haven't been able to find a material.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[JoshPlumSE]

In general, vibrations are related to mass and stiffness and damping. So, the most common ways to change the response (outside of changing the applied loads) is to change the mass, stiffness or damping of the floor.

1) Change the Stiffness. You could add columns to reduce the spans. Add beams to certain areas to stiffen up those areas. Note: Having bays that are not the same span / stiffness can be a good thing because it reduces the likelihood that the vibrations will propogate across multiple bays.

You could also add FRP coatings to the slab bottom and top. Not sure how much this increased the stiffness, but I'm guessing it does.

2) I'm going to assume that changing mass isn't an option.

3) Regarding damping: I think there are some products that can be attached to the underside of a slab that can increase damping. Probably won't be cheap. But, I think it's possible.

 

[dik]

I don't think FRP will change the stiffness significantly... if the slab were failing because of strength, then yes...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[bones206]

There could possibly be something done with the layout of the cubicles and pathways to minimize the worst vibrations currently being experienced. Probably a long shot but worth exploring as it would be an inexpensive fix.

 

[Agent666]

Make everyone walk along the stiffer beam lines to improve the response out in the floor if you have some control over the architectural layout?

https://engineervsheep.com