MIxed Use Project - Garage Vibrations 1

[Martino8]

Wondering if we should spend some time looking at vibrations on this project
It's 5 levels of wood framed apartments over 3 levels of PT conrete two way slabs.

We're curious if vibrations created from the parking use on the lowest two levels could potentialy transmit upward, through the top concrete "podium" level and into the living space above.
My initial thinking was that a two-way PT system (columns spaced less than 28 feet) should create a lot less vibration compared with other garage systems (say 60ft precast or steel beams).

Any thoughts, past experience, or vibration analysis recommendations?
Thanks everyone

 

[271828]

I've asked about this before. My impression is that it'll likely be OK if you don't have speed bumps.

 

[KootK]

I think that you'll be okay too. Presumably that transfer slab has some mass to it to dampen things some, both it's own mass and the mass supported above.

More importantly, I don't really know how I'd go about tackling this meaningfully as a vibration problem. Predicting the vertical transmission of vibrations accurately is a good deal harder than dealing with horizontal transmission in my experience.

 

[271828]

...I don't really know how I'd go about tackling this meaningfully as a vibration problem. ...

I had to deal with this once and couldn't find much in the literature.

I considered a speed bump to be the worst case scenario, so I used that as the load case. I calculated the time it would take for a wheel to go to the top of the hump and derived a rough impulse force. Fed that into a time history analysis and computed the acceleration. There were no measurements. I would expect the real values to be off by quite a bit. I told them no speed bumps, so that would hopefully result in a conservative design.

Some papers, in case anybody would want to go digging into the references:

Evans, J.B. (2006), "Garage structure vibration transmission to human occupied spaces," Thirteenth International Congress on Sound and Vibration.

Khorshid, E., Alkalby, F., Kamal, H. (2007), "Measurement of whole-body vibration exposure from speed control humps," Journal of Sound and Vibration. [info on speed bump geometry etc)

Watts, G.R. and Krylov, V.V. (2000), "Ground-borne vibration generated by vehicles crossing road humps and speed control cushions," Applied Acoustics.