Wood is the oldest of the structural materials. It has been used since prehistoric times. Wood can be shaped with simple tools, and it can be easily fastened with nails, screws, or adhesives. It is available either as lumber, which is a natural wood, or as glued laminated timber. This latter formis much stronger and consists of specially selected and prepared wood laminations securely bonded together with glue or adhesives. The laminations do not exceed in thickness. Glued laminated beams are available in a variety of shapes. Both lumber and glued timber is widely inbuilding construction.Wood contains certain natural defects, such as knots, shakes, etc., which require that it be stress-traded to establish design or allowable stress values for particular members. Another important factor is the grain of the wood .The allowable stress in compression parallel to the grain,for instance, is higher than the allowable stress perpendicular to the grain. 木材是最古老的结构材料。自史前时代已经过去。形成的木材可以用简单的工具，它可以轻松的紧固螺钉，钉，或粘合剂。它可以作为木材，这是一种天然的木材，或胶合木。这后一种方式更强大的和由特别挑选和准备的木材牢固地粘结在一起的叠片胶或粘合剂。叠层的厚度不超过。胶合层积梁在各种形状可供选择。无论是木材、胶合木材广泛中建设。木材有一定的天然缺陷，如结，摇摇头，等，这要求它应力交易来建立特定的成员或容许应力设计值。另一个重要的因素是木头的纹理。许用应力在顺纹压缩，例如，高于垂直于晶粒的许用应力。
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