Cyclopedia of architecture, carpentry, and building : a general reference work . on the swinging win-dow when it is fullyopened. Doors may consistentirely of wood, of aframe of angles coveredwith corrugated steel,or of corrugated steelalone. The first twoclasses may be so fixedthat they will slide, asin the folding doors ofresidences; open out-ward like a commondoor; lift vertically; or,in case they are madeentirely of corrugatedsteel, roll up like a win-dow-shade. This latter door is a patented one. Shop doors areseldom made to open outward or inward, on account of the spacerequired—a space w
Cyclopedia of architecture, carpentry, and building : a general reference work . on the swinging win-dow when it is fullyopened. Doors may consistentirely of wood, of aframe of angles coveredwith corrugated steel,or of corrugated steelalone. The first twoclasses may be so fixedthat they will slide, asin the folding doors ofresidences; open out-ward like a commondoor; lift vertically; or,in case they are madeentirely of corrugatedsteel, roll up like a win-dow-shade. This latter door is a patented one. Shop doors areseldom made to open outward or inward, on account of the spacerequired—a space which can be devoted to better purposes. , 91, and 92 show details of the above doors. Let it be required to design the girt when the trusses are 16feet apart and the girts are 5 feet center to center. The moment . 5 X 10 X 30 X 16 X 12 „ „,,„ , . , , ., IS = oi 600 pound-uiches; and the re-quired section modulus is -^-^- . = Bv inspecting the tables lo 000 in the Carnegie Handbook, pp. 97 to- 119, it is found that the fol-lowing shapes will be sufficient:. Section Q-aTig. 90. Detail of a Wooden Door. 284 ROOF TRUSSES 71 Shape Section Modulus One 5-inch I-beam One 6-inch channel One 4yV by S^-inch zee-bar One 6 by 4 by y^-inch angle From this it is evident that the channel is the most efficient andeconomical. 23. Columns. Columns may consist of almost any combina-tion of shapes, either latticed or connected by plates. Some of themost common cross-sections areshown in Fig. 93, those illustratedin b and c being used to a greatextent. The advantage of theseforms is that they give a smallradius of gyration about the axisb-h, and a larger one about theaxis a-a (see Fig. 94). This isespecially desirable, since, in ad-dition to the direct stress due tothe weight of the cranes, rooftruss, and covering, the columnmust withstand the moment dueto the wind and to the eccentric-ity of the runway girder. Bothof
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