Vibration-floor steel joists on steel beams

[WWTEng]

25'x30' bay. Steel joists @ 2''6" oc with concrete on metal deck. End supports are W16 beams (spanning 25'). Occupancy is office area, could be used as classroom. So basically its bar joists sitting on beams instead of masonry walls. Could vibration be a problem?

This project is in its very preliminary stages, just found about it last night. I am looking for some experience based input if this arrangement seems like a potential case for vibration study.

 

[JoshPlumSE]

Do some Design Guide 11 calculations to see. There's no way way for us to know without knowing more about the weight of the system and thickness of the slab.

 

[MiketheEngineer]

Maybe - but I doubt it. More info needed

 

[WWTEng]

Josh, agreed. I am doing that now.

 

[spats]

Echo JoshPlum, but I think there's a good chance a thicker slab will be required. I used to do office floors with a 3" slab on form deck with joists and beams all the time, before we worried about vibration. You'll find this won't work vibration-wise, especially with a 30' bay. You'll probably need at least a 4" slab. If you have relatively large open spaces without a lot of walls/partitions, system damping is low. I think a better system is composite beam/composite deck with secondary beams placed 5'-6' on center. You can go composite with joists, but it doesn't help the vibration numbers because the joists are considered composite for vibration purposes already.

 

[msquared48]

With enough bass, there could be a problem. Just make sure it is not the floor of the music room.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[haynewp]

You can add extended ends from the joists to the girders as you may know, which help some. I like composite beams for floors.

 

[efsinc]

No calcs based comments for you here, but ran this question buy a steel joist manufacturer engineer I know, many years with Vulcraft. Asked him: "in your experience, what floor spans or floor conditions become more susceptible to vibration problems?" His reply utilized a technical term I had not heard used before regarding floor structures, but I think I catch his drift....
"28'- 31' K series at 2' o/c with 1 1/2" Concrete is a pure bounce house."