Treesearch

A relatively simple test procedure was developed to evaluate the behavior of various adhesives near fire-exposed surfaces in laminated constructions. A number of sections cut from laminated blocks were exposed to fire on one surface. After this exposure, the sections were transversely cut, and the gluelines were examined for separation depth. In addition, the cool specimens were broken along the glue joints so as to be able to determine the residual bonded area. An equation incorporating both the separation depth and the residual bonded area at the joints was utilized to obtain a bdegradati...

This analysis of a mass increment core sampling of eight coniferous species of Maine characterizes specific gravity for each of the species. No clear-cut relationships of specific gravity to forest type, stand density class, height class, or tree diameter at breast height were found. Included in the data are the species average specific gravity and the range. These data can be used in the assembly of working equations for weight scaling, pulp yield estimation, and strength evaluation.

Successive stages of decay in the sapwood of sweetgum (Liquidambar styraciflua L.), a hardwood, and of southern pine (Pinus sp.), a softwood, were observed microscopically. The white-rot fungus. Polyporus versicolor L., and the brown-rot fungus, Poria monticola Murr., were the fungi used or the observations, light microscopy, plus the techniques of polarization and ultraviolet-absorption microscopy, was used on sections 4 microns thick cut from celloidin-embedded specimens. For both fungi, hyphae were widespread in the early stages of decay in both types of wood. The hyphae of the white...

Gives the general resistance to decay of a number of native wood species grown in the United States, and some factors affecting decay resistance.

Historically, log quality has been evaluated by log grading systems based on judgment and experience. The hardwood log grades for standard lumber, as developed by the Forest Products Laboratory, are based on an analysis of the relationship between log characteristics and end product yield.This system enables foresters, timber sellers, and timber buyers to separate, from woods-run hardwood logs, those logs suitable for manufacture into factory grade lumber and to rank the logs into categories of high-, medium-, and low-quality yields.The yield tables provide the information necessary for...

This paper discusses the assumptions used in the statistical theory of strength, shows the application of the theory to wood bending members, and gives a comparison between theory and actual data for wood beams.

Requests are frequently received by the Forest Products Laboratory to examine warped plywood, veneered table tops, or similar products, to explain the cause of the warping, and if possible to suggest measures to remedy the difficulty.

The mechanical behavior of a flexible epoxy-resin adhesive system was observed in joints of plywood to lumber. The joints were subjected to internal swelling stresses caused by an increase in moisture content. Previous experimental work at the U.S. Forest Products Laboratory has shown that this adhesive system acts as a strain-absorbing cushion and thus has a significant stress-relieving effect in the joint. An attempt was made to use this adhesive as a calibrated tool for measuring shear strain as a function of lumber size, lumber specific gravity, and glueline thickness in a plywood-to-lu...

A new system of wood-frame house construction has been developed which combines increased use of low-grade wood, prefinished components, and rapid field assembly methods without much divergence from conventional construction. Laboratory evaluations of the components of the Nu-frame system indicated that; (a) 4-foot spacing of the W-trusses tested provides a safety factor of three over design load, (b) the wall framing system with 4-footspacing of double 2- by 4-inch studs (Nu-frame) is a reasonable method of construction, (c) the use of a l/2-inch fiber board filler between studs (Insul-2)...

The owner of a small quantity of green lumber or logs is often confronted with seasoning it to a state of dryness suitable for use in furniture, wood carving, or other handiwork. He cannot follow the practice of commercial mills, which employ dry kilns for the purpose. because kilns are too costly. On the other hand, air seasoning outdoors usually does not dry lumber sufficiently for such uses, although it is sufficient for structures that will be used outdoors. Green lumber can be seasoned to the necessary dryness for the purpose by combining outdoor air seasoning with subsequent further...