Quarles, S. L. and Tully, D.F
|Wood is perhaps the most comfortable and familiar construction material, and has long been associated with structures used for human habitation. The long-term performance of wood in service is heavily influenced by exposure to biological and non-biological factors. Common forms of biological degradation include that by fungi (decay), insects (e.g., termites and beetles), and marine borers (e.g., Limnoria and Teredo). Degradation by bacteria has been documented, especially under anaerobic conditions, but this damage occurs slowly, and is rarely a problem in structures. Common forms of non-biological degradation include weathering and corrosion, but can also result from extended exposure to acid or alkaline conditions, and high temperatures. In addition, certain treatments, such as preservative and fire retardant treatments, which are intended to provide greater protection for wood thereby improving overall durability, can result in reduced design strength. All of these factors can result in reduced service life, but in most cases appropriate design and selection of the wood material, coupled with the knowledge of in-service exposure, can result in predictable long-term performance. An excellent source for discussions of specific types of biological and non-biological degradation in wood was presented in Meyers and Kellogg (1982). A more general discussion of these factors has also been published by ASCE (1982).
In this paper, factors which can lead to reduced performance will be discussed, and design details and appropriate selection which can aid in providing long term performance in service will be reviewed. Where applicable, documents that provide more details or information than can be given here will be cited.
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