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Re: Steel Framing - Aerobic vibration criterion

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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 -----
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