Treesearch

The Graves Crossing bridge was constructed October 1991 in Antrim County, Michigan, as part of the demonstration timber bridge program sponsored by the USDA Forest Service. The bridge is a two-span continuous, stress-laminated deck superstructure and it is 36-ft long and 26-ft wide. The bridge is one of the first stress-laminated deck bridges to be built of sawn lumber treated with chromated copper arsenate (CCA) preservative. The performance of the bridge was continuously monitored for 2 years, beginning at the time of installation. This performance monitoring involved gathering and...

The degradation of wood treated with fire retardant (FR) chemicals in roof systems is a problem of major national significance. Understanding of this phenomenon is limited by lack of information on how the performance of FR-treated wood in the laboratory correlates to that of FR-treated wood in the field. In this study, five outdoor field exposure chambers were constructed near Madison, Wisconsin, in the summer of 1991. These structures were intended to simulate the batticsc of multifamily structures for which model building codes sometimes allow the use of FR-treated roof sheathing....

Bolted connections often fail by a shear plug or a splitting beneath the bolt caused by tension perpendicular-to-grain stresses as the bolt wedges its way through the wood. Preventing this type of failure would enhance the capacity and reliability of the bolted connection, thus increasing the overall integrity of a timber structure and enabling wood to compete favorably with other engineering materials. This research investigated the use of fiberglass reinforcement to enhance the load-carrying capacity of bolted wood connections. A series of specimens were prepared from standard 38- by...

The commercial value of several softwood species of the northeastern United States could be increased if these woods could be treated to meet existing American Wood Preserversa Association (AWPA) Standards and used in durable structures. We evaluated the long-term durability of incised and unincised white pine, red pine, eastern spruce, balsam fir, and eastern hemlock treated with ammoniacal copper arsenate (ACA) and chromated copper arsenate (CCA1Type C). The treated wood was exposed above ground and in ground contact in the southern and northeastern United States. Simulated decks were...

To satisfy the increased demand for forest products, much of the future timber supply is expected to be derived from improved trees grown on managed plantations. This fast-grown resource will tend to be harvested in short-age rotations and will contain higher proportions of juvenile wood compared with wood in current harvests. As a result, current allowable properties may need to be reduced in the future. This report explores four options for monitoring the properties of fastgrown wood and briefly discusses the advantages and disadvantages of these approaches. The recommended multiple-stage...

More than 1,200 sawmills produce the bulk of U.S. and Canadian softwood lumber. The maps and tables in this report show the location and size of these mills by State and Province. Analysis of timber inventories in relation to use shows a close correspondence between pricing and use intensity. In some Southern States, the intensity of use is approaching recent growth levels, but the adoption of more intensive management coupled with maturing of large areas of newly established forests should increase supply over the next two decades.

Much discussion has been held regarding the merits of laboratory decay tests compared with field tests to evaluate wood preservatives. In this study, procedural aspects of soil jar decay tests with 1 cm 3 blocks were critically examined. Differences among individual bottles were a major source of variation in this method. The reproducibility and sensitivity of the soil-jar method using small blocks must be further characterized before it can be accepted as a standard protocol for evaluating preservative-treated wood.

Natureas engineering of wood through genetics, stand conditions, and environment creates wide variability in wood as a material, which in turn introduces difficulties in wood processing and utilization. Manufacturers sometimes find it difficult to consistently process wood into quality products because of its wide range of properties. The primary objective of this study was to investigate the usefulness of a stress wave technique for evaluating wood strength and stiffness of young-growth western hemlock and Sitka spruce in standing trees. A secondary objective was to determine if the...

An intensive decline and mortality problem is affecting yellow-cedar trees in southeast Alaska. Yellow-cedar snags (dead trees) could be important to the economy in southeast Alaska, if some high-value uses for the snags could be established. Due to the high decay resistance of yellow-cedar, the rate of deterioration is so slow that snags may remain standing for a century or more after death. Obtaining information on wood properties from these snags is necessary to correctly assess the utilization potential of the yellow-cedar. Initial property analyses, Phase I, showed no evidence that...

This report describes the development of a test method and predictive model to estimate the residual bending strength of fire-retardant-treated plywood roof sheathing from measurement of screw-withdrawal force. The preferred test methodology is described in detail. Models were developed to predict loss in mean and lower prediction bounds for plywood bending strength as a function of a screw-withdrawal force. Our analysis of fire-retardant-treated plywood from three different studies, each with various fire-retardant-treatment, processing, plywood thickness, and exposure temperature...