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RE: NDS Flat Use Factor

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Timber Construction Manual, 4th ed., American Institute of Timber Construction, page 4-102.
"The bending design values for sawn lumber loaded about the x-x axis are obtained by adjusting the tabular design value by the appropriate size factor CF .  When lumber is loaded about the y-y axis (flatwise), these tabular design values in bending are further multiplied by the flat use factor, Cfu.
Roger Davis
SDS Architects, Inc.
-----Original Message-----
From: Nels Roselund, SE [mailto:njineer(--nospam--at)]
Sent: Tuesday, January 29, 2002 7:31 PM
To: seaint(--nospam--at)
Subject: NDS Flat Use Factor

The 1997 NDS Supplement provides a Size Factor CF for beam members used with loads applied to the narrow face.  For Flat Use, factor Cfu is given.
Because of the word "also" in the explanation of Cfu, my interpretation of the use of the factors is that the allowable flexure value for flat use is based on using both the Size Factor and the Flat Use factor so that Fallow = Fb x CF x Cfu.  Is that correct?
Nels Roselund
Structural Engineer
South San Gabriel, CA