Cyclopedia of architecture, carpentry, and building : a general reference work . case of thatat point Lq. The stresses in knee-braces depend upon the height and also thewidth of the building. The stresses may be computed according tothe methods of the next article, and the knee-bracing should be 239 26 ROOF TRUSSES designed accordingly. The inspection of a number of plans seems toindicate that the sizes of knee-braces vary from two angles 2^ by 2^by J-inch for spans of 30 feet and a height of building of 35 feet, totwo angles 4 by 3 by yVi^ch for a span of 70 feet and a height ofbuilding to th
Cyclopedia of architecture, carpentry, and building : a general reference work . case of thatat point Lq. The stresses in knee-braces depend upon the height and also thewidth of the building. The stresses may be computed according tothe methods of the next article, and the knee-bracing should be 239 26 ROOF TRUSSES designed accordingly. The inspection of a number of plans seems toindicate that the sizes of knee-braces vary from two angles 2^ by 2^by J-inch for spans of 30 feet and a height of building of 35 feet, totwo angles 4 by 3 by yVi^ch for a span of 70 feet and a height ofbuilding to the top of the truss of 75 feet. In case of roof trusses with the chords nearly parallel (see , p. 2), the stresses, on account of the small depth, are usuallyquite large, and much heavier members than above mentioned arerequired. In some cases, 6 by 6-inch angles with 8-inch plates areused, and connection plates of f to ^ inch are common. In cases where the trusses are subjected to the action of corrosivegases, the thickness of the members should be made greater than that. Fig. 41. Bending Tendency, Ends Free. Fig. 43. Bending Tendency, Ends Fixed. required by the design alone, since corrosion will decrease the sectionconsiderably, and this should be allowed for. 10. The Steel Truss=Bent. When a truss is connected to steelcolumns at its ends and by means of knee-bracing (see Fig. 39), itforms what is called a steel truss-bent. The stresses in the trussdue to the roof covering and snow loads are the same as when it issupported by a masonry wall; but the wind stresses are different. Thewind blowing on the roof and also on the sides of the building, causesstresses in the truss. The wind on the building is transferred to thecolumns, which, by means of the knee-braces, cause stresses in thetruss. The whole bent tends to bend as shown in Fig. 41 if the endsof the columns rest on masonry pedesta^ls. If the ends of the columnsare securely bolted to heavy masonry pedestals so that t
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