Date of Award

Summer 8-25-2018

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Douglas Gardner

Second Committee Member

Mehdi Tajvidi

Third Committee Member

Aaron Weiskittel

Abstract

PERIODIC EVALUATION OF NORTHEASTERN SPRUCE AND BALSAM FIR LUMBER PROPERTIES

By Benjamin Farber

Advisors: Dr. Douglas Gardner

An Abstract of the Thesis Presented

In Partial Fulfilment of the Requirements for the

Degree of Master of Science

(In Forest Resources)

August 2018

In the past two decades, proportions of juvenile wood have increased in lumber cut from intensively managed Southern yellow pine (Pinus spp.) plantation-based forests. Knowing that a decrease in rotation age can increase proportions of juvenile wood, which in turn negatively affects mechanical properties in lumber, the SYP grouping was evaluated to determine if the published design values in the National Design Specification (NDS) required a downward adjustment. In 2011, following extensive testing, the American Lumber Standards Committee (ALSC) required that design values for SYP be reduced by 30 percent. As a result of this, ASTM D1990-16 was revised to include required periodic monitoring of all lumber species groupings to detect possible downward shifts in mechanical properties. The Northeastern Lumber Manufacturing Association (NELMA) conducts monitoring programs approximately every five years within the Northeast and Great Lakes regions, two of the three regions where SPF(s) lumber is produced (the third region is in the Western U.S. which is monitored by the Western Wood Products Association (WWPA)). The monitoring program described herein, as required by ASTM D1990-16, evaluates bending properties of balsam fir (Abies balsamea) and the Eastern spruces (Picea rubens, Picea glauca, Picea mariana and Picea abies) for No.2 grade 2” x 4” lumber. In addition to the required 2” x 4” size this research program also evaluated 2” x 6” and 2” x 8”.

The monitoring program requires testing and subsequent analysis follows ASTM standards D1990-16 and D4761-13, the latter specifying testing procedures for static bending tests of lumber.

After lumber flexural failure, procedures outlined in ASTM D4761-13 were applied to each specimen to diagram and quantify the failure behavior and create a failure code. This failure code is used in the determination of the strength ratio which is then used to calculate Grade Quality Index (GQI), which is used to determine if further lumber mechanical property adjustments are required.

The 2” x 4” modulus of rupture (MOR) and modulus of elasticity (MOE) values derived from this testing program were statistically compared to the three separate testing programs. The 2” x 6” and 2” x 8” values from the 2017 monitoring program, were compared with the 1991 values and showed a decrease in MOR and MOE. Further testing of the 2” x 6” and 2” x 8” No. 2 nominal widths should be conducted in future testing programs to investigate any possible downward shift in mechanical property values.

A Wilcoxon test showed that the 2” x 4” samples of both species had similar MOE values when compared with the 1991 design values, but did show a downward shift in values when comparing the MOR values. A Tukey HSD reported similar results reporting the MOE as statistically the same as the 1991 values for both species, whereas the mean MOR was statistically lower. These findings are still considered preliminary as this programs results will be pooled together with the two future monitoring programs and combined with the remaining species within SPF(s). After final submission to the ALSC, The SPF(s) pooled values will be re-evaluated.

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