Skip to page content
USDA Forest Service

Research & Development Treesearch

Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern Research Station
Help - We Participate  Government Made Easy

Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

View PDF (240 KB bytes)

Title: Fiber stress values for design of glulam timber utility structures

Author: Hernandez, R.; Moody, R. C.; Falk, R. H.;


Source: (Research paper FPL ; RP-532):23 p. : ill. ; 28 cm.

Publication Series: Research Paper (RP)

Description: In this study, we developed a simple equation to calculate average fiber stress values for design of glued-laminated (glulam) timber utility structures as a function of design bending stress. We took design stress in bending values specified by the American Institute of Timber Construction (AITC) for various combinations of glulam timber, applied appropriate end-use adjustments, and determined an appropriate factor to obtain average modulus of rupture. Fiber stresses for glulam were then determined from the average modulus of rupture values using the relationship between these values and the fiber stress values for round timber poles. To verify this relationship, a data base was compiled that contained bending strength results of glulam timber beams manufactured following the design combinations established by the AITC. Results indicate that the proposed equation can be used to calculate fiber stresses for all glulam beams manufactured with visually graded or E-rated lumber. For bending members less than 50 ft (15.24 m) long, the average fiber stress was found to be approximately 2.7 times the design stress in bending.

Keywords: Laminated wood, Poles, Design calculations, Utility poles, Fiber stresses, Douglas-fir, Southern pine, Design stresses

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.



Hernandez, R.; Moody, R. C.; Falk, R. H. Fiber stress values for design of glulam timber utility structures. (Research paper FPL ; RP-532):23 p. : ill. ; 28 cm.


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.