Reducing annoying floor vibrations – interesting paper
I found an interesting paper on reducing annoying floor vibrations. I thought it might be useful so I am sharing it here.
The gist of the recommendations are:
1. Use a higher live load of at least 40 psf in calculations.
2. Go up one size in joist depth over code min or use L/600 deflection limits.
3. Glue and screw the floor sheathing.
4. Use strongbacks with floor trusses.
5. With TJIs, discuss specific vibration concerns with manufacturers.
6. With solid sawn joists, multiply the maximum L/360 span by 0.91 / Use 40 psf live-load and live-load deflection of L/480 for joist spans up to 20 ft.
The main reason for these methods is to increase the stiffness of the floor to increase the natural frequency of the floor above 15 Hz. Humans are apparently most sensitive to vibrational frequencies around 7-10 Hz. The stiffer the floor, the higher the natural frequency.
2012 was a bit ago, so maybe some of the recommendations have changed.
I’m editing in Akos’s notes because they seemed rather salient:
“What is not intuitive is that when you are looking at longer spans, even something considered stiff (ie l/480) can be bouncy. A small increase in span can significantly reduce the natural frequency of the assembly, it doesn’t scale linearly at all. Once you get 20’+ clear span, deflection criteria no longer works, you have to check natural frequency. Manufacturer’s design software is definitely a big help.
The biggest issue is that sometimes getting non-bouncy floors can double the floor joist budget. I’ve ran into and it took a lot of self convincing that is worth the cost.”
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