Essentials in the theory of framed structures . Pig. 105. 148 THEORY OF FRAMED STRUCTURES Chap. IV is the influence line for M2, when the load of i lb. is betweenLo and L2. Now it may be observed that the influence line ONQ for if 2is identical with the influence line which was drawn, when thecriterion for maximum bending moment at the center of theloo-ft. girder was required in Article 90. Hence, the criterionand position of an E-40 train are the same in each case. It wasfound in Article 90 that wheels 11, 12 and 13 at the center,. -4S)25=/00Pig. 106. satisfied the criterion for a maximum ben
Essentials in the theory of framed structures . Pig. 105. 148 THEORY OF FRAMED STRUCTURES Chap. IV is the influence line for M2, when the load of i lb. is betweenLo and L2. Now it may be observed that the influence line ONQ for if 2is identical with the influence line which was drawn, when thecriterion for maximum bending moment at the center of theloo-ft. girder was required in Article 90. Hence, the criterionand position of an E-40 train are the same in each case. It wasfound in Article 90 that wheels 11, 12 and 13 at the center,. -4S)25=/00Pig. 106. satisfied the criterion for a maximum bending moment; wheel12 giving the greatest maximum, or 3,219 98. Illustrative Problem. Determine the stress in U1U2 for an E-40 loading when wheel12 is at Z^ (Fig. 106). There are seven forces acting on the truss—five floor beamloads and two truss reactions. After the floor beam loadsand the resulting truss reactions have been determined,the stress in U1U2 may be obtained by finding the sum ofthe moments about L2 of all the forces acting on one side(either side) of a section through panel 1-2, and dividing thesum by 32. SM of the floor beam loads about X o = X 25 = 1, X 5° = 3, X 75 = 3, X 100 = 2,720 100)11,754 = truss reaction at Lo Sec. Ill BRIDGES 149 SM about Z,2 of the forces on the left of the X SO = 5,877 X 25 = 1, X 50 = 1,360 2,65832)3^219 = compressive stress in UiUi-The problem may be solved more quickly by consideri
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