Essentials in the theory of framed structures . and L91L3; one-half is placed on segment 0-3 formaximum stress in U2U3. 100. The stress in a web memberof a parallel chord truss is usuallydetermined by passing a sectionthrough the web member and twochord members, in such a mannerthat the truss is cut into two por-tions. The shear, or algebraic sum, of the vertical forces actingon one side (either side) of the section, equals the vertical com-ponent of the stress in the web member. loi. Influence Line for Shear in a Panel.—The criterion forthe vertical component of the maximum stress in U1L2 (Fi
Essentials in the theory of framed structures . and L91L3; one-half is placed on segment 0-3 formaximum stress in U2U3. 100. The stress in a web memberof a parallel chord truss is usuallydetermined by passing a sectionthrough the web member and twochord members, in such a mannerthat the truss is cut into two por-tions. The shear, or algebraic sum, of the vertical forces actingon one side (either side) of the section, equals the vertical com-ponent of the stress in the web member. loi. Influence Line for Shear in a Panel.—The criterion forthe vertical component of the maximum stress in U1L2 () will be developed by drawing an influence line, showing thevariation of the shear in panel 1-2 as a load of i lb. moves acrossthe span. When the load of i lb. is between Z4 and L2, the shear in thepanel equals the left reaction;, which increases from o to i lb. asthe load moves from Li to Lq. Hence, the line OT is theinfluence line for shear in the panel, when the load of i lb. isbetween Li and L2; and TV = +3^. When the load of i Fig. 108. 152 THEORY OF FRAMED STRUCTURES Chap. IV is between Lo and Li, the shear in the panel is the right reactiontaken negatively. Therefore QS is the influence line for shearin the panel, when the load of i lb. is between Lo and Li; and us= -y^. When the load of i lb. is in the panel, or between Lx and L^,there are two forces acting on either side of the section. On theleft, there are the truss reaction at Lo and the floor beam loadat Li; while on the right there are the truss reaction at L4 andthe floor-beam load at L^. Let the load of i lb. be in the paneland at a distance x from Li. Consider the forces on the leftof the section, and let K represent the truss reaction at Lo, y thefloor-beam load at L\ and F the shear in the panel 1-2; then n 50 -t- X J X R = -—— and r = — 100 25 F = R-r= 5°-3^ ICO This equation, being of the first degree, may be represented by astraight line. When the load of i lb. is at L2, x = o, and^ = K
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectstructu, bookyear1922
