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Wood products can be protected from the attack of decay fungi, harmful insects, or marine borers by applying chemical preservatives. Preservative treatments greatly increase the life of wood structures, thus reducing replacement costs and allowing more efficient use of forest resources. The degree of protection achieved depends on the preservative used and the proper penetration and retention of the chemicals. Some preservatives are more effective than others, and some are more adaptable to certain use requirements. To obtain long-term effectiveness, adequate penetration and retention are...

Structural analysis mathematically models the physical forces, deformations, and stresses acting within a system. Structural analysis may generally apply to the construction of aircraft, bridges, buildings, furniture, pallets and shipping containers, sculpture, sporting equipment, and tools. In other words, structural analysis is useful in nearly every aspect of wood engineering. The ability to model deformations and stresses under load naturally lends itself to efficient design and, ultimately, effective use of materials.

A large portion of wood products made today are glued, or bonded, together. This is because bonding allows wood to be used in ways that would be impossible otherwise. We take wooden sheet materials, such as plywood, for granted, but they perform far better in some ways, and are far less expensive, than solid wood alternatives. Large structural pieces, such as the glulam skeletons in many buildings, would be impractical without adhesives. Everyday items such as wooden chairs would be extremely difficult to build without adhesives. In short, bonding wood products increases their value. This...

Because wood properties vary among species, between trees of the same species, and between pieces from the same tree, solid wood cannot match reconstituted wood in the range of properties that can be controlled. Wood with localized defects (such as knots) can often be utilized effectively in wood-based composites. When wood with defects is reduced to wood elements, the influence of these characteristics in the manufactured product is reduced. To reinforce sustainable harvesting efforts, wood derived from small-diameter timber, forest residues, or exotic and invasive species may also be...

The term composite is used to describe any wood material bonded together with adhesives. The current product mix ranges from fiberboard to laminated beams and components. For this chapter, wood-based composite materials are classified into the following categories: panel products (plywood, oriented strandboard (OSB), particleboard, fiberboard, medium-density fiberboard (MDF), hardboard); structural timber products (glued-laminated timber (glulam), laminated veneer lumber (LVL), laminated strand lumber, parallel strand lumber); and wood–nonwood composites (wood fiber–thermoplastics,...

In the living tree, wood contains large quantities of water. As green wood dries, most of the water is removed. The moisture remaining in the wood tends to come to equilibrium with the relative humidity of the surrounding air. Correct drying, handling, and storage of wood will minimize moisture content changes that might occur after drying when the wood is in service. If moisture content is controlled within reasonable limits by such methods, major problems from dimensional changes can usually be avoided. The discussion in this chapter is concerned with moisture content determination,...

When sawn, a log yields round timber, ties, or lumber of varying quality. This chapter presents a general discussion of grading, standards, and specifications for these commercial products. In a broad sense, commercial lumber is any lumber that is bought or sold in the normal channels of commerce. Commercial lumber may be found in a variety of forms, species, and types, and in various commercial establishments, both wholesale and retail. Most commercial lumber is graded by standardized rules that make purchasing more or less uniform throughout the country. Round timbers and ties represent...

Round timbers, ties, and lumber sawn from a log, regardless of species and size, are quite variable in mechanical properties. Pieces may differ in strength by several hundred percent. For simplicity and economy in use, pieces of wood of similar mechanical properties are placed in categories called stress grades, which are characterized by (a) one or more sorting criteria, (b) a set of properties for engineering design, and (c) a unique grade name. The most familiar system is that for lumber. Sorting criteria have also been established for round timbers and ties. This chapter briefly...

The strength and stability of any structure depend heavily on the fastenings that hold its parts together. One prime advantage of wood as a structural material is the ease with which wood structural parts can be joined together with a wide variety of fastenings—nails, spikes, screws, bolts, lag screws, drift pins, staples, and metal connectors of various types. For utmost rigidity, strength, and service, each type of fastening requires joint designs adapted to the strength properties of wood along and across the grain and to dimensional changes that may occur with changes in moisture content.

There is no property of wood—physical, mechanical, chemical, biological, or technological—that is not fundamentally derived from the fact that wood is formed to meet the needs of the living tree. To accomplish any of these functions, wood must have cells that are designed and interconnected in ways sufficient to perform these functions. These three functions have influenced the evolution of approximately 150,000 different species of woody plants, each with unique properties, uses, and capabilities, in both plant and human contexts. Understanding the basic requirements dictated by these...