Floor Vibration

[JArchie]

I am in the process of analyzing a composite floor for vibration due to heel-drop. The floor framing consists of special pre-fab joists spanning 46' and spaced at 14'. this means that the 6.25" (3", 16 ga composite deck) slab is spanning 14' between joists (ouch!). I'd like to use the latest AISC 11 - "Floor Vibrations Due to Human Activity" by Murray, but I do not have the section properties of the special joists, and there are no shop drawings available. I have also heard of Murray's FloorVib2 program to assess natural frequencies of floors and required damping, but I would need to input the joist data which I do not have. Any suggestions?

 

[SacreBleu]

This doesn't make sense - if the manufacturer of the joists is known, why don't you contact them for your needed info?
Deck spanning 14'? Who made that decision?

 

[jike]

What do you mean by special pre-fab joists? Are they steel?composite or non-composite?

 

[JArchie]

Sorry, but I failed to mention this is a forensic evaluation of a building constructed in 1995. I do not know the steel joist manufacturer, and it is a composite slab. The joists are 36" deep and are spaced at 14'. As far as the 14' deck span is concerned, the Engineer-of Record made that decision I assume.

 

[jike]

Have you checked the metal tags on the joists? They usually list the manufacturer and the joist size. You ought to be able to then get the capacity from SJI tables.

If you measure the top chord and the bottom chord sizes, you ought to be able to calculate the effective moment of inertia from that. Calculate the neutral axis location and then sum up the A D^2 for each chord about the NA. I think that they recommend that you take 85% for the effective moment of inertia.