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RE: Suspended Speaker

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Alfonso,
Here is what I think:
If the speaker is free to move, so it's not statically
stable. Then no force will apply on that. But the
supporting truss should be designed not only for
seismic force due to speaker weight (if it's part of
effective dead load), but also for the forces and
vibrations caused by speaker movement. And it seems to
me that the second part may have important local
effect on truss design in both force and deformation
criteria. It's notable that the speaker weight is only
300 lbs. So the vibration is more important than
static load.
Frank


--- Alfonso S Quilala <aquilala(--nospam--at)taylorgaines.com>
wrote:
> I think the question I supposed to ask is, "Is it
> allowed not to seismically
> brace the speaker due to the reason I previously
> mentioned (seismic is not
> required for elements that are suspended and free to
> translate during a
> seismic event for more than the expected earth
> displacements)."
>  
> The speaker by the way will be installed in a high
> school gymnasium and
> auditorium.
>  
> Thanks again!
>  
> Alfonso S. Quilala Jr., P.E.
> 
> -----Original Message-----
> From: Mark D. Anderson PE
> [mailto:mark(--nospam--at)alaskaengineer.com]
> Sent: Wednesday, February 07, 2001 2:56 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Suspended Speaker
> 
> 
> Are you looking for something beyond footnotes 11
> and 12 to Table 16-O in
> the 1997 UBC?
>  
> Mark D. Anderson PE
> 
> ----- Original Message ----- 
> From: Alfonso S Quilala
> <mailto:aquilala(--nospam--at)taylorgaines.com>  
> To: 'seaint(--nospam--at)seaint.org' <mailto:'seaint(--nospam--at)seaint.org'>
>  
> Sent: Wednesday, February 07, 2001 9:10 AM
> Subject: Suspended Speaker
> 
> 
> I am reviewing a submittal consist of 300 lbs.
> speaker cluster that is to be
> suspended using an aircraft cable.  It will be
> attached to the midpoint of a
> bottom chord of a truss.  The Structural Engineer
> noted in his calcs. that
> seismic is not required for elements that are
> suspended and free to
> translate during a seismic event for more than the
> expected earth
> displacements.  I think that I have read this note
> somewhere before but I
> can not recall where.  I tried to asked my co-worker
> and tried to look at
> the Code but I can not find it.  Will somebody point
> me where I can find it?
> 
> 
> Thanks a lot in advance! 
> 
> Alfonso S. Quilala Jr., P.E. 
> 
> 


=====
Fariborz Tehrani,                      Phone: (310)801-4237
Civil Engineer                           Fax: (530)481-9532
BSCE, MSCE, PE                    Voice Mail: (877)743-6206
email: fmtehrani(--nospam--at)msn.com
web: www.fmtehrani.com

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