History of Wood Investigation and the Development of Standards
Early Investigations of Wood Properties
Human beings have been building with timber for millennia. Evidence of timber construction has been found in many of the earliest human societies. It is this history and familiarity with timber that allowed for the building of some of the world’s most magnificent structures, including the roof trusses of Palazzo Vecchio in Florence, Italy; Westminster Abbey in London; the stave church at Borgund, Norway; and the Horyuji Temple in Ikaruga, Nara Prefecture, Japan. All of these structures were built well before the strength properties of wood were well understood and documented. Yet, they still stand today. For the most part, tradition and experience governed construction with timber until the late 19th and early 20th centuries.
One of the earliest individuals to investigate the properties of wood was Theophrastus (372-287 B.C.E.) in ancient Greece. He is best known as the successor of Aristotle, but he spent much of his time in botanical investigations. His nine volumes on Enquiry into Plants and six on Causes of Plants were the primary resources on botany well into the Middle Ages. In volume five of Enquiry into Plants, called Of The Timber Of Various Trees And Its Uses, Theophrastus outlines his investigations on the properties of wood (knots, texture, ease of use, hardness and heaviness), its relative strength (which woods can best support weight), and best uses (for ships, houses, and types of carpentry).
More specific investigations in to the properties of building materials did not occur until the 17th and 18th centuries. Galileo took time from his study of the heavens in the 1630s to investigate the strength of building materials, including wood. His description of a tension test was the first known attempt at measuring that particular property (Booth, 1964). Knowledge of other types of failure was advanced in the late 17th century when Mariotte, Hooke and Parent looked at the failure of cantilevered and fixed beams (Booth, 1964).
chenbroek, however, in the mid-18th century was responsible for the greatest early advances in testing wood. He developed a machine to test tensile strength, used it on various species and cuts of wood, examined the buckling of columns and failure of confined timbers, and studied the effects of moisture content on wood density and strength. During this time, Buffon was also studying the failure of large wood beams (up to 30 feet long), and examining the effect of load duration. The findings of his experiments on both small clear specimens and large beams were reproduced in tabular form. He ultimately concluded that it wasn’t possible to predict properties of large wood members from the test of small specimens without defects (Booth, 1964; Sganzin, 1828).