Cyclopedia of Architecture, Carpentry and Building Volume 3; A General Reference Work (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. 1909 Excerpt: ...is GEFF'E'G, and Sloolbs. 3loo IbS. F'E' (0,250 pounds compression) represents the stress in f'e. Since E'G = 0, the wind produces no stress in member go'. At joint (5) three members are connected together and there is no load. The sides of the polygon for the joint must be parallel to the members joined there. Since two of those members are in the same straight line, two sides of the polygon will be parallel and it follows as a consequence that the third side must be zero. Hence the stress in the member e'd equals zero and the stresses inyV and d'c' are equal. This result may be explained slightly differently: Of the stresses in e'f, e'd and d'c" we know the first (6,250) and it is represented by E'F'. Hence we draw from F' a line parallel to c'd' and one from E' parallel to d'e and mark their intersection D'. Then the polygon for the joint is E'F'C'D'E, ' CD' (6,250 pounds compression) representing the stress in c'd'. Since E' and D' refer to the same point, E'D' scales zero and there is no stress in e'd'. The stress in ad' can be determined in various ways. Since at joint (6) there are but two forces (the stresses in ge' and e'd' being zero), the two forces must be equal and opposite to balance. Hence the stress in d'a is a tension and its value is 3,600 pounds. 2. It is required to analyze the truss represented in Fig. 24 for wind pressure, the distance between trusses being 15 feet. The length 13 equals l/202 + 14' or v/400 + 106 = 24.4 feet. Hence the area sustaining the wind pressure to be borne by one truss equals 24.4 X 15 = 366 square feet. The tangent of the angle which the roof makes with the horizontal equals 14-f-20 = 0.7; hence the angle is practically 35 degrees. According to Art. 10, the wind pressures for elopes of 30 and 40 degrees a...