Cyclopedia of architecture, carpentry, and building : a general reference work . =+8 180 bending moment at b is: A/b = 14 X 5 360 - 4 X 6 400 = 49 440 pound-feet; and the bendingmoment at 6is: Mh- = 5 360 X 14=75 040 pound-feet. The forces intheir proper di-rection are nowplaced on a dia-gram of the truss(Fig. 47), and thestresses are solvedby the method ofStatics. The stressdiagram is givenin Fig. 45, and thestress record inTable VII. The above for-mula are for caseswhen the columnsare free at thelower end. Whenthe columns arenot free, they arecalled fixed; that Fig. 47. Position,
Cyclopedia of architecture, carpentry, and building : a general reference work . =+8 180 bending moment at b is: A/b = 14 X 5 360 - 4 X 6 400 = 49 440 pound-feet; and the bendingmoment at 6is: Mh- = 5 360 X 14=75 040 pound-feet. The forces intheir proper di-rection are nowplaced on a dia-gram of the truss(Fig. 47), and thestresses are solvedby the method ofStatics. The stressdiagram is givenin Fig. 45, and thestress record inTable VII. The above for-mula are for caseswhen the columnsare free at thelower end. Whenthe columns arenot free, they arecalled fixed; that Fig. 47. Position, Direction, and Intensity of Exterior Forces. ^S, tliey are Sup-posed to be sotightly connected that they cannot move when the post bends asshown in Fig. 42. In such cases the result is the same as if thecolumns were shortened by an amonut n -r- 2, and the followingformuloe result (see Fig. 48): Fig. 46. Position, Direction, and Intensity of Wind Forces,Ends J44 ROOF TRUSSES 31 TABLE VIIStress Record of Truss=Bent under Wind Load Member Stress Member Stress x-z -15 700 9-10, !i-IZ 4- 6 500 X-3 -15 700 12-13,14 -15 300 X-6 -10 700 Y-4 + 6 500 X-7 -10700 Y-8 - 1 900 X-9 -f- 1 500 Y-IZ - 9 600 X-/3 -M 5400 - 1 300 1-2 + 5 ZOO 1-Y -t 8 640 Z-3 - Z4I0 15-Y -Z 1 440 3-4 ?i- Q 500 A-l - 8 180 4-5 - 7 500 C-15 + 6 514 5-6 + 2 700 b-c - 3457 6-7 - 2410 b-c - 5 193 7-8 -f II 000 9-IO-JI 0 8-9 - 7 600 13-14 0 V-^ + c^ u;i a (?n + -^) = Wu + TT, lSab= + H.(m+-^)-W,(^) m n iSbc= + TF, (| + ^) + n-h (I + ^ + ~2-) - TT^ . 3^ /Sbc = T^a?+ ^) + m.(m + -J+ -f) + H. 2 m 245 32 ROOF TRUSSES £,, = 7)1 Bending moment at b= il/i, = Hi -^ TT, (— —) Bending moment at b = M\>> = Hn —^. For the truss-bent of Fig. 45, when the columns are fixed at thebase, the stresses are the same as if the cohimns were shortened by anamount n -t- 2, as above mentioned. The bent would then appear asin Fig. 49, and the values of the various stresses
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