. Handbook of railroad construction; for the use of American engineers. Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States .. . all-ing E the horizontal distance between the vertical suspend-ers, we have the formula X=-riXa, in which we place E, 2 E, 3 E, etc., in place of Y, thus call-ing the rods one hundred feet apart, we have Centre. 00 Rodl. 1002 Rod 2. X a X80 4E^ 2002 -, X 80 500- Rod 3. 9E^3002 Xa ^2X80 500■ Rod 4. 1££2400 2 X a 500 X 80 Rod 5. 25^2500 2 X a
. Handbook of railroad construction; for the use of American engineers. Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States .. . all-ing E the horizontal distance between the vertical suspend-ers, we have the formula X=-riXa, in which we place E, 2 E, 3 E, etc., in place of Y, thus call-ing the rods one hundred feet apart, we have Centre. 00 Rodl. 1002 Rod 2. X a X80 4E^ 2002 -, X 80 500- Rod 3. 9E^3002 Xa ^2X80 500■ Rod 4. 1££2400 2 X a 500 X 80 Rod 5. 25^2500 2 X a 500 X 80 Problem 3. 227. To find the angle E C G, fig. 103. The formula forthe angle between the axis of the tower, and the tangent tothe curve of the cable at the point of suspension is 2atanga = ECG=-T-. Span being one thousand feet, b is five hundred; and aibeing eighty feet, we have IRON BRIDGES. 207 160tangECG = ^ = logl60 —log500: or — = tang = 17° 45 = E C , 90° —17° 45 = 72° 15 = angle G C A, or A C H. When the points of suspension are not at the same eleva-tion, we proceed in the same manner: only using F G, G E,in place of E F, E C, in fig. 103 A. Fig. 103 That the resultant of the forces acting upon the top ofthe tower may be vertical, the angles G C A, and A C H,fig. 103, must be equal; if not, the masonry must be soarranged as to cause the resultant to pass through thecentre of gravity. When more than one span is used, andthe openings are unequal, that the intermediate pier or piersshall not be pulled over, the cable of the largest, and con-sequently heaviest span, must have a greater inclinationfrom the horizontal than that of the shorter span; theproduct of the tensions by their respective inclinationsmust be equal. Mr. Roeblings plan in connecting severalspans, is to attach the cables of adjacent spans to a pendu- 208 HANDBOOK OF RAILROAD CONSTRUCTION. lum upon the pier, by which arrangement the differe
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