Banner for LabNotes
From Lab Notes
Contact Information
Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53726-2398
Phone: (608) 231-9200
Fax: (608) 231-9592


You are here: FPL Home  / Information Products & Services  / Publications

Requested Product

Title: Mechanical grading of oak timbers

Source: Journal of materials in civil engineering. Vol. 11, no. 2 (May 1999).:p. 91-97 : ill.

Author(s)Kretschmann, David E.; Green, David W.

Publication Year: 1999  View PDF »

Category: Journal Articles

Abstract: For many wood species, the grading of timbers [>76 mm (>4-in.) thick] has not changed in decades. Most timbers are still visually graded by methods that originated in the 1930s. Mechanical grading procedures used to accurately grade 38-mm (2-in. nominal) dimension lumber have not been adapted for use with timbers. Furthermore, the only reliable timber test data available for most softwood species were obtained near the turn of the 20th century, and no test data are available for hardwood timber. The lack of better grading procedures and test data makes it likely that current property assignments for timbers are wasteful. Given that the reduced availability of lumber is expected to continue well into the 21st century, the structural engineer must have the widest possible options for structural timbers. Therefore, a study was conducted by the USDA Forest Service, Forest Products Laboratory, to examine use of a pulse echo stress wave technique along the length of timbers to estimate modulus of elasticity (MOE) of green timbers and the development of a machine stress rated grade for oak timbers. Two hundred and ninety-five untreated 178- by 229-mm (7- by 9-in.) mixed oak timbers, 4.9 m (16 ft) in length, were measured weighted, and nondestructively evaluated to determine their pulse echo MOE. Two hundred twenty were destructively tested in bending; 75 were tested to failure in compression parallel to the grain. The results of these tests determined relationships between pulse echo MOE and static bending MOE and between bending and compressive strength. These tests suggests a clear potential of establishing a machine stress rated grade for oak timbers. This article discusses the implication of these results, potential commercial grades, and a follow-up study to qualify the suggested grades.

Keywords: Quercus; Grading; Mechanical methods; Structural timbers; Modulus of elasticity; Strength testing.

File size: 261 kb(s)

This publication is also viewable on Treesearch:  view
RITS Product ID: 21935
Current FPL Scientist associated with this product
Kretschmann, David E.
Research General Engineer

Additional items that might interest you
View the video celebrating FPL's 100 years of public service in 2010, from the producers of the Greatest Good....view

Research Highlights from FPL....view

Termite Eradication: A search for the Holy Grail.... view

Moisture Management in Residential Construction Series videos...view

Wood Floor Systems in Residential Construction Series videos....view
- FPL's Mission and Strategic Plan -

FPL's mission is to identify and conduct innovative wood and fiber utilization research that contributes to conservation and productivity of the forest resource, thereby sustaining forests, the economy, and quality of life. ... ..more »

- FPL Research Emphasis Areas -
Advanced Composites

As an integral part of the FPL mission, we improve the long-term sustainability of our Nation's forests by creating valuable composite products from biobased materials ... ..more »

Advanced Structures

The FPL has been in the forefront of wood-frame housing research since 1910 and has long been recognized as a world leader in such housing-related areas as engineered wood ... ..more »

Forest Biorefinery

We all know the compelling reasons that the United States needs to reduce its dependence on fossil fuels. Historically, the greatest increases in energy demand have been for transportation fuels ... ..more »


A leader in wood products research for over a century, the FPL is positioning itself to become the lead Federal research facility for the application of nanotechnology in forest products ... more »

Woody Biomass Utilization

Forests in the United States contain a substantial amount of small-diameter, overstocked, and underutilized material.FPL research projects are exploring the potential of the small-diameter ... ..more »