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RE: PSL Beam creep

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Dan,
There is an excellent page on the Trus-Joist website located at:
http://www.trusjoist.com/tin/mst1.cfm#introf

Generally, manufactured wood products are produced and delivered to the
jobsite with lower moisture contents than conventional lumber. As the
article notes, most lumber will dry on the construction site while
manufactured lumber will take on moisture. Therefore, if the relative
Humidity is exceptionally high, the changes in creep and stiffness are
much greater in manufactured lumber than in stick lumber. 

I think you will find the resources you need on this site. I also
commend TJ on their site - almost all of the information you need is
available immediately.

Dennis S. Wish, PE
California Professional Engineer
The Structuralist.Net Information Infrastructure
 
Website: 
http://www.structuralist.net
 
Professional Forum: 
http://www.structuralist.net/cgi-local/yabb/YaBB.cgi
 
Public Forum on Housing: 
http://www.structuralist.net/cgi-local/yabb2/YaBB.cgi

-----Original Message-----
From: dmorrow(--nospam--at)swensonsayfaget.com [mailto:dmorrow(--nospam--at)swensonsayfaget.com] 
Sent: Tuesday, December 11, 2001 2:19 PM
To: seaint(--nospam--at)seaint.org
Subject: PSL Beam creep

Has anyone had problems with PSL beams creeping (deflecting) when they
are
wet or have elevated moisture contents?  I have a wet PSL beam which has
deflected 4x what it should be deflecting given the load conditions.
The
beam is wet (as is most of the other framing) because the contractor
didn't
close-in the structure during recent heavy rains and winds.  The
contractor
is saying the beam is under-sized.  PSL material seems more prone to
strength loss when wet and it seems to wick water more than standard
lumber.
Any experiences or thoughts.
TIA



Dan Morrow
Swenson Say Fagét
2124 3rd Ave. Suite 100
Seattle, WA  98121
206-956-3745 (direct)
206-443-4870 (fax)

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