The unit load to be used in connection with the influence lines will be taken at 10,000 pounds. Remembering that the panel lengths are each 30 feet, it will be seen that the panel-point _Q_ is 150 feet from _A_. Hence the product _gx_ will be 1,500,000 foot-pounds. Similarly the product _g_(l - _x_) will be 900,000 foot-pounds. Laying off the first of these quantities, as _AD_, at a scale of 1,000,000 foot-pounds per linear inch, and the second quantity, as _BK_, by the same scale, the influence line _ACB_ can at once be completed. Vertical lines are next to be drawn through the positions of the various weights, including one through the centre of the uniform train-load 110 feet in length resting on the truss. The vertical line through the centre of the uniform train-load is shown at _O_. By carefully scaling the vertical intercepts between _AB_ and _ACB_, and remembering that each of the loads on the truss must be divided by 10,000, the following tabulated statement will be obtained, the sum of the intercepts for each set of equal weights being added into one item, and all the items of intercepts being multiplied by 1,000,000: .195 × 110 × .4 × 1,000,000 = 8,580,000 foot-pounds. 1.78 × 2.6 × ” = 4,628,000 ” ” 2.14 × 4 × ” = 8,560,000 ” ” .485 × 2 × ” = 970,000 ” ” 1.525 × 2.6 × ” = 3,965,000 ” ” .9 × 4 × ” = 3,600,000 ” ” .12 × 2 × ” = 240,000 ” ” ---------- 2⟌30,543,000 ” ” ---------- Moment for one truss = 15,271,500 ” ” The lever-arm of _ef_, i.e., the normal distance from _Q_ to _ef_, is 39.7 feet. Hence the stress in _ef_ is 15,271,500 ----------- = 384,700 pounds. 39.7 All the chord stresses can obviously be found in the same manner. In order to place the same moving load so as to produce the greatest shear at the same section _Q_, the criterion of equation (33) must be employed. The dimensions of the truss shown in connection with Fig. 29 give the following data to be used in that equation: _i_ = 210 feet, _m_ = 60 feet, and _p_ = 30 feet. _l_(_m + i_) _l_ Hence ------------ = 10²/₇, --- = 1¹/₇. _pi i_ [Illustration: FIG. 25_b_.] [Illustration: FIG. 25_c_.] [Illustration: FIG. 25_d_.]