Mechanics of engineeringComprising statics and dynamics of solids: and the mechanics of the materials of constructions, or strength and elasticity of beams, columns, arches, shafts, etc . libriumpolygon formed from a force-diagram whose load-line con-sists of the actual loads on the span laid off in properorder, can now be drawn, a convenient value for H havingbeen selected (the same Hfor all the spans, that the moment-carves of successive spans may form a continuous line forthe whole girder); since we may easily compute the propermoment ordinate at each support to represent the actualmoment,
Mechanics of engineeringComprising statics and dynamics of solids: and the mechanics of the materials of constructions, or strength and elasticity of beams, columns, arches, shafts, etc . libriumpolygon formed from a force-diagram whose load-line con-sists of the actual loads on the span laid off in properorder, can now be drawn, a convenient value for H havingbeen selected (the same Hfor all the spans, that the moment-carves of successive spans may form a continuous line forthe whole girder); since we may easily compute the propermoment ordinate at each support to represent the actualmoment, then, for the H adopted, by (3) § 397. Themoment-curve of each span, since we know its two extremepoints and its pole-distance H, is then constructed by§ 341. (4.) The shear. Since the last construction involvesdrawing the special force-diagram for each span, with aray corresponding to each part of the span between twoconsecutive loads, the shear at any section of the beam iseasily found as being the length of the vertical projectionof the proper ray, interpreted by the force-scale of theforce-diagram, as in §§ 389 and 390. With the shears as CONTINUOUS GIRDER BY GRAPHICS. 507. Fig. 449. librium, , IY = 0 (§ 36), we have ordinates a shear-diagram maynow be constructed, if desired, foreach span. The directions of theshears should be carefully noted.(5.) Reactions of supports. Letus consider free the small por-tion of the girder, at each pointof support, included between twosections, one close to the supporton each side, Fig. 449. Supposeit is the support C, and call thereaction, or pressure at that sup-port Bc. Then, for vertical equi- ne— ^CR+eA: CL (5) and, in general, the reaction at a support equals the(algebraic) sum of the two shears, one close to the supportou the right, the other on the left. The meaning of thesubscripts is evident. In applying this rule, however, afree body like that in Fig. 449 should always be drawn, orconceived; for the two shears are not
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectenginee, bookyear1888
