Treesearch

This paper finalizes research on graded Douglas-fir 2 by 4 beams subjected to constant bending loads of various levels and durations. Compared to results for testing in a controlled environment, results confirm that load duration did not appear to be shortened by tests in an uncontrolled environment, at least extending out to 12-plus years. By the same comparison, relative creep was considerably increased, however. The extended data also confirm that no evidence was found for a threshold below which stress levels for lumber can be maintained indefinitely. Based on the finalized prediction...

The objective of this study was to investigate the influence of juvenile wood on the mechanical and physical properties of red alder. Tree growth in the first 10 to 20 years, usually referred to as juvenile wood, often influences wood quality by adversely affecting mechanical strength properties. Strength can be reduced up to 50 percent by the presence of juvenile wood. More knowledge of juvenile/mature wood properties will provide practical information for silviculturists and processors of red alder, leading to a more appropriate usage of this species. Six red alder trees were used in...

Yellow-cedar trees have been mysteriously dying for more than a century in southeast Alaska. As these stems continue to stand for decades in the forest, foliage, twigs, and branches deteriorate. The sapwood in the stem degrades, leaving columns of essentially heartwood standing like ghosts in the forest until they eventually drop. To estimate the potential for utilization of these trees, several experiments have been initiated to characterize the natural durability of heartwood from dying and dead yellow-cedar trees. The objectives of this study were to characterize the durability of...

A direct proportionality has been found between the smoke extinction area (SEA) for smoke of room linings and the SEA as measured in the cone calorimeter (ISO5660). The room test scenario (ISO9705) considered was the propane ignition burner at the corner with a 100/300 kW program and the specimen lined on the walls only. The mixing of smoke from propane and lining flames in the hot vitiated ceiling layer and within the exhaust system was modeled by adding contributions from heat release rates of propane and linings separately as a function of time. With overventilation and flaming generally...

Research and demonstration bridge projects to further develop wood for transportation structures increased substantially in the United States in 1988 under a legislative action by the U.S. Congress known as the Timber Bridge Initiative. This program, renamed the Wood in Transportation Program, continues today and is administered by the Forest Service. FHWA became involved in timber bridge research in 1990. The FHWA program increased substantially under the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). From 1992 to 1997, ISTEA authorized significant funding for timber...

Recently AASHTO adopted a load and resistance factor design code for highway bridges. The new code provides a rational basis for the design of steel and concrete structures. However, the calibration was not done for wood bridges. Therefore, there is a need to fill this gap. The development of statistical models for wood bridge structures is discussed. Recent test results provided a considerable amount of new data for sawed wood and glulam components. Statistical methods provide a good tool for development of rational models for loads and resistance. Because of the random nature of load and...

The increased interest in copper-based wood preservatives has hastened the need for understanding why some fungi are able to attack copper-treated wood. Due in part to accumulation of oxalic acid by brown-rot fungi and visualization of copper oxalate crystals in wood decayed by known copper-tolerant decay fungi, oxalic acid has been implicated in copper tolerance by the formation of copper oxalate crystals. Nineteen isolates of the brown-rot fungus Wolfiporia cocos were evaluated for oxalic acid production and weight loss on wood treated with 1.2% copper citrate. Twelve of 19 isolates that...

Bioremediation of chromated copper arsenate-treated waste wood with one or more metal-tolerant bacteria is a potential method of naturally releasing metals from treated wood fibre. Sampling eight environments with elevated levels of copper, chromium, and arsenic resulted in the isolation of 28 bacteria with the capability of releasing one or more of the components from chromated copper arsenate-treated wood. The isolates represent 13 species of 8 different genera of soil-inhabiting bacteria. Three isolates, Acinetobacter calcoaceticus FN02, Aureobacterium esteroaromaticum VV03, and...

Recovery of chromated copper arsenate (CCA)-treated wood for reuse has been the focus of several international research groups due to the imminent disposal problem created when large quantities of CCA-treated wood ultimately come out of service. Bioleaching with Bacillus licheniformis CC01 and oxalic acid extraction are two methods known to remove significant quantities of metals from CCA-treated wood. Remediated particulate CCA-treated southern pine was reassembled into particleboard (PB) using 10% urea-formaldehyde resin. Particleboard panels were evaluated for internal bond (IB),...

This paper compares two new formulations of creosote and one pigment-emulsified creosote (PEC) with a formulation of creosote that met requirements of the AWPA standard P1/P13. Two softwood and two hardwood species were treated to four retention levels with each formulation. The evaluation of the four creosote formulations was done using (1) soil-block tests, (2) fungal cellar tests, and (3) field tests. This paper briefly discusses results from the soil-block tests, and updates previous reports to three years of fungal cellar tests and five years of field exposure in Saucier, Mississippi....