Civil Engineering; A Text-Book for a Short Course (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ...degree of stiffness under bending forces is essential in timbers exposed to considerable stress, to prevent the undue deformation of the structure. The stiffness of wood ordinarily varies directly with its weight and strength to resist flexure, and inversely with the amount of moisture in it. Tension..... Compression. Shearing.... Bending. Torsion Modulus of lo ticity... Hardness.--Hardness measures the ability of the wood to resist abrasion and indentation, and is an important quality in floors, tenons, mortises, etc. The hardness of wood also varies directly with its weight, and inversely with the amount of moisture in it. The maximum hardness of any specimen is developed by placing the fibers in the direction of the applied force. Flexibility.--Flexibility is the property of bending without rupture. This property of wood is developed by moistening, by steaming, and by reducing the material to a form in which one or both of the dimensions of the cross-section are small as compared with the length. Toughness.--Toughness measures the capacity of the wood to resist shock; it is a function of both strength and flexibility. Defects. Defects in timber are due to peculiarities of growth and treatment, to the action of moisture, and to the action of insects. Defects due to Growth and Treatment.--These are windshakes, circular cracks separating the annual rings which are caused by the twisting action of the wind; belted timber, a term applied to timber which has been killed by girdling before felling; knots, defects caused by the growth of the wood at limbs which impair the ease of working and strength; twists, a term applied to timber having a spiral grain; heart-shakes, splits in the center of the tree; star-shakes, splits radiating from the center; checks, crac...