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I faxed you pertinent pages from the 1977 NDS®, but to address your questions:
1) Yes, the size factor, C_F, was applicable to glulam. It was (12/d)^(1/9)
2) The slenderness factor C_s was part of the buckling equation for beams and not directly multiplied by F_b to obtain F_b'. It was used to determine if the beam was short, intermediate, or long.  It was then used in either the intermediate or long beam equation. However, F_b used in the intermediate equation was not to be modified by C_F. You would use C_F after using the intermediate or long buckling equation. You'll  hopefully see that more clearly in the fax  
Let me know if you have additional questions.

John "Buddy" Showalter, P.E.
Director, Technical Media
AF&PA/American Wood Council
1111 19th Street, NW, Suite 800
Washington, DC 20036
P: 202-463-2769
F: 202-463-2791

The American Wood Council (AWC) is the wood products division of the American Forest & Paper Association (AF&PA). AWC develops internationally recognized standards for wood design and construction. Its efforts with building codes and standards, engineering and research, and technology transfer ensure proper application for engineered and traditional wood products.

The guidance provided herein is not a formal interpretation of any AF&PA standard.  Interpretations of AF&PA standards are only available through a formal process outlined in AF&PA's standards development procedures.


-----Original Message-----
From: Sharon [mailto:sharon(--nospam--at)]
Sent: Monday, February 13, 2006 7:01 PM
To: AWCInfo(--nospam--at)
Subject: FW: 1976 UBC GLULAM

I just posted the following to the list.  Maybe you can help.

Since I now have the 1976 UBC but not the 1978 NDS I would appreciate some help clarifying the following please:


When applying the modification factors to tabulated Fb, it appears that 'CF' (size effect factor) was applicable for Glulams as well as 'CS' (slenderness factor) per the UBC.

·         Is it true that 'CF' (size effect factor) was applicable for Glulams?

·         Is Fb' = tabulated FbxCFxCS or least of tabulated FbxCF or tabulated FbxCS



Sharon Robertson, P.E.

Arcon Engineers


Tel: 858-503-7854

Fax: 858-503-7858