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PSL Beam creep

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There was an article in Frame Building News, November, 2000, "Long Term 
Deflection (Creep) of a Wood I-Joist/OSB Residential Floor," by Benjamin 
Wisniewski and Dr. Harvey Manbeck.  The article describes the deflection of 
such a floor under "normal" humidity ranges, 30 to 84 percent, and does not 
address deflection if wet.  Even under these conditions, they report that the 
deflection of the floor system is 57 percent higher than that of a comparable 
sawn joist and plywood floor system.

The biographies of the authors indicates that Wisniewski is with LZA 
Technology and Manbeck is a professor in the Agricultural Engineering 
Department at Penn State University.  Perhaps they may have personal 
information that would be helpful to you.


A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Dan Morrow wrote:

. > 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

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