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 . tj MECHANICS OF ENGINEERING. 472 we obtain the values of the thrust and shear for the sec-tion at m. When found in this way for a number of pointsalong the rib their values may be laid off as vertical linesfrom a horizontal axis, in the verticals containing the re-spective points, and thus a thrust diagram and a shear dia-gram may be formed, as constructed in Fig. 433. Noticethat where the moment is a maximum
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 . tj MECHANICS OF ENGINEERING. 472 we obtain the values of the thrust and shear for the sec-tion at m. When found in this way for a number of pointsalong the rib their values may be laid off as vertical linesfrom a horizontal axis, in the verticals containing the re-spective points, and thus a thrust diagram and a shear dia-gram may be formed, as constructed in Fig. 433. Noticethat where the moment is a maximum or minimum theshear changes sign (compare § 240), either gradually or. Fig. 433. suddenly, according as the max. or mm. occurs betweentwo loads or in passing a load; see m, e. g. Also it is evident, from the geometrical relations involv-ed, that at those points of the rib where the tangent-lineis parallel to the proper ray of the force diagram, thethrust is a maximum (a local maximum) the moment (of ARCH-RIBS. 473 stress couple) is either a maximum or a minimum and theshear is zero. .From the moment, Hz = -?-!_, p2 — —t- e 1 may be computed. From the thrust = Fpu p{=-—==—, (F F — area of cross-section) may be computed. Hence thegreatest compression per sq. inch (pi~\-p2) may be found ineach section. A separate stress-diagram might be con-structed for this quantity (pi+p2). Its max. value (afteradding the stress due to change of temperature, or to rib-shortening, for ribs of less than three hinges), wherever itoccurs in the rib, must be made safe by proper designingof the rib. The maximum shear Jm can be used as in §256to determine thickness of
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectenginee, bookyear1888
