American Architect and Architecture Volume 93 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 edition. Excerpt: ... to the ground. There is a possibility that if fire started in one of these high buildings it would develop into a conflagration before the fire department could gain control."----Ncw York Hernia. It is not until the moisture in the substance of the cell walls is dravn upon that the strength of the wood begins to increase. Scientifically, this point is known as the "fiber-saturation point." From this condition to that of absolute dryness the gain in the strength of wood is somewhat remarkable. In the case of spruce the strength is multiplied four times; indeed, spruce, in small sizes, thoroughly dried in an oven, is as strong, weight for weight. as steel. Even after the reabsorption of moisture, when the wood is again exposed to the air, the strength of the sticks is still from 50 to 150 per cent. greater than when it is green. VVhen, in drying, the fiber-saturation point is passed, the strength of wood increases as drying progresses, in accordance with a definite law, and this law can be used to calculate from the strength of a stick at one degree of moisture what its strength will be at any other degree. Manufacturers, engineers and builders need to know not only the strength, but the weakness of the materials they use, and for this reason they are quite as much interested in knowing how timbers are affected by moisture as they are in knowing how they are weakened by knots, checks, cross-grain and other defects. It is clear that where timbers are certain to be weakened by excessive moisture they will have to be used in larger sizes for safety. So far, engineers of timber tests, while showing that small pieces gain greatly in strength, do not advise counting on the same results in the seasoning of large timbers, owing to...