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Wood Creep

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Peder,

See Chapter 4 (page 37 et. seq.) of the "Wood Handbook" published by the 
Forest Products Lab. which is available free from the FPL web site, 
<http://www.fpl.gov>.  Creep is related to sustained stress, temperature and 
humidity.  Here in the dry desert, I will typically use a multiplier of 2 to 
account for creep.

HTH

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

Peder Golberg wrote:

. > Anybody know of the relationship between wood creep and the species of 
. > wood?  Is creep based on Modulus of Elasticity or something else.    I 
. > have a long span glu-lam beam (46 ft long) that is Alaska Yellow Cedar.  
. > This beam is protected from direct rain (wind might cause rain to hit the 
. > beam) and it is located outside and in always sunny Portland, Oregon 
. > (FYI, it is raining very hard outside right now).   I planned/designed 
. > for a camber of 1.5 times the dead load deflection to account for some 
. > creep but the actual creep after one year is about 1 1/2 times the 
. > calculated dead load deflection.   The camber was there originally 
. > (although it wasn't measured) and the beam wasn't installed upside down. 
. > The gutters that once drained water now don't based on the deflection.    
. > Is creep different for Cedar compared to Douglas Fir besides in the value 
. > for Modulus of Elasticity?

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