11.1 INTRODUCTION TO WOOD AS A MATERIAL

Wood is unique among all engineering materials used for structural applications in that it is the only one that is renewable. Wood, after all, comes from trees, and trees grow naturally. This is the "good news" and the "bad news," however. The good news is that most of the work of "manufacturing" wood is done for us by Nature through the processes of life and growth in the tree from which the wood comes. Hence, wood is a particularly practical and economical material. Even the lumber we extract from the wood of trees is relatively inexpensive. All that's needed is to harvest trees, cut the usable parts of the trees to size to produce the lumber desired, ^[1] and dry (or "season") the lumber before it is ready for use. The bad news is that because wood is produced by trees and trees are a product of Nature, we have little control over the product. Unlike for other structural materials such as metals, polymers, ceramics, glass, composites, and even concrete, we can do little to adjust or refine the wood's properties to suit our needs. At least in the past, we had to accept wood's natural strengths and limitations. But, as will be seen in Section 11.3, we are not totally at Nature's mercy any longer.

Wood is more than a utilitarian structural material. It is also generally the best loved of all materials that we use for building things. There are...