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FWD>[SEAOC] Truss cambering

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Mail*Link(r) Remote           FWD>[SEAOC] Truss cambering
Ghassem Khosrwonia:

The cambering of trusses is a standard practice of the truss industry; in fact,
they ALWAYS camber unless you SPECIFICALLY tell them not to do so. This criteria
is specified in the Steel Joist Institute standard specs.  The better way to
deal with camber is to specify a camber related to dead load deflection;
however, you will need to supply the APPROPRIATE portion of dead load for which
you want the camber to be computed.  The issue of camber is of particular
importance for long-span floor systems, which are often controlled by the need
to address vibratory response; the typically stiffer floor trusses would be
overcambered if you allow the industry-standard camber to be used.  The result: 
when you place floor decking and concrete fill, the camber won't come out of the
truss and your concrete will be too thin at mid-span (or too thick at the
edges).
--------------------------------------
Date: 2/1/96 2:48 PM
From: seaoc(--nospam--at)seaoc.org
     To those experienced:
     
     1. At what point costs of cambering vs costs of increasing member size 
     will offset one another. Do you think pound per pound, cambering of 
     long span trusses is more expensive that just adding muscle?
     
     2. is it sufficient to show camber amount at the top chord alone, or 
     should the values be shown for the bottom chord also, although it 
     seems they would be the same.
     
     3. Any idea on source of information on cambering of long span 
     trusses?
     
     I appreciate any responses.
     
     Thanks, Ghassem Khosrwonia





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