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Re: Steel Framing - Aerobic vibration criterion

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Also, thickening your slab or concrete fill over metal deck will get you more mass and perhaps more efficient use of materials rather than making the beams do all the work. Usually your beam is so big that it still works just fine for the added dead load since vibration governs.

As you are finding out, vibration has a huge effect on steel framing requirements (often doubling the weight per square foot) over areas designed for the same live load.

Make sure you have framing that is continuous over girders (meaning they line up on both sides of the girder, not necessarily moment continuity). Spans greater than 30 feet and you are looking at W30's - yes. Spans in the 24 foot range you should be able to get W24x94's in that range to work at a 7 or 8 foot spacing.

Floorvibe is a good program and AISC also has a similar program on their website you can download for free. Both are based on design guide 11. Floorvibe can work inside and outside of RAMsteel I believe.

I would not recommend using Etabs for vibration design as it appears to be very conservative.

-gm

On Thu, Jul 23, 2009 at 3:35 PM, Stuart, Matthew <mStuart(--nospam--at)cmxengineering.com> wrote:
Thanks Steve

________________________________

From: SGE Structural [mailto:sgordin(--nospam--at)sgeconsulting.com]
Sent: Thu 7/23/2009 6:03 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Steel Framing - Aerobic vibration criterion


Matthew,

Design Guide 11 has an example proving he vibration inadequacy of about the same structure.  The example concludes that the most effective way is to achieve the required rigidity is to put columns at the girder mid-spans.

Although this appears to be the best way, I would still recommend to try to get a consultation from Dr. Thomas Murray.  He is very responsive and, of course, would provide the best advice on the vibration issues.

V. Steve Gordin, SE
Irvine CA



       ----- Original Message -----
       From: Stuart, Matthew <mailto:mStuart(--nospam--at)cmxengineering.com>
       To: seaint(--nospam--at)seaint.org
       Sent: Thursday, July 23, 2009 14:39
       Subject: FW: Steel Framing - Aerobic vibration criterion


       Posted on behave of another engineer at CMX:

       Hello All,



       I am in the process of designing a new composite slab on steel framing system for basketball and racquetball use as well as cardio activities.    It's a new 13'000 ft^2 mezzanine.   The approximate column grid is 30' x 31'.



       I am following the requirements for vibration criteria for aerobic type of floors per AISC design guide 11 - Chapter 5.   Per table 5.3, the minimum required floor frequency for an aerobic floor is 9 to 10 Hz.   I am having a difficult time trying to achieve this frequency even after significantly increasing the size of both interior and exterior girders (e.g., W30 x 116 & W24 x 55 respectively) as well as the typical beams (W21 x 44 although for stresses and deflection - even a W14 x22 or W16 x 26 could work).  I've even divided the 30'-0" bay into 4 spaces yielding 7'-6" spacing for the filler beams.   These sizes get me a mere 6 Hz?  While it may be possible to achieve the required frequency by increasing the beam and girder sizes even more, the sizes will be so large and uneconomical.



       Does anyone have any prior experience designing composite slab on steel framing systems for such vibration criteria?   I am looking for a reality check on member sizes?  Any guidance/suggestions would be greatly appreciated?



       Please let me know ASAP.



       Thanks.

       Ashu Patel, P.E.

        Project Manager
       Structural Department
       CMX
       200 State Highway Nine
       Manalapan, NJ 07726-0900
       Phone (732) 577-9000 ext. 334
       Fax (732) 577-9888
       website: www.cmxengineering.com