Friday, July 24, 2009

RE: Steel Framing - Aerobic vibration criterion

The cheapest means of controlling vibration is to add mass.  It is much more efficient and cost effective than adding stiffness.  Go to a thicker concrete slab with normal weight concrete. 
 
Another approach is to add distributed mass dampers.  This method has been employed many many times.  I used it in the 1970's to control the vibration at a shopping mall by suspending concrete weights from springs. 
 
There is also a manufacturer of plastic containers that are suspended by springs and attached to the deck from below.  The plastic containers are filled with water until you get the appropriate mass for the damping you desire.  I can not recall the manufacturer. 
 
 http://www.aees.org.au/Proceedings/2006_Papers/257_Saidi_et_al.pdf

Regards, Harold Sprague


 
Subject: FW: Steel Framing - Aerobic vibration criterion
Date: Thu, 23 Jul 2009 17:39:44 -0400
From: mStuart@cmxengineering.com
To: seaint@seaint.org

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

 


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