WEIGHTS OF RAILWAY BRIDGES. 



151 



A diagramatic sketch of a truss railway bridge is shown in Fig. I. The names of the different 

 iiit-iiil>ers are shown on the diagram. The floor may be carried on two or more stringers. Two 

 M i in^ri ^ .ire commonly used for an open timber floor and two or four stringers for a ballasted floor. 



A railway steel trestle is shown in Fig. 2. Steel trestles are commonly built with the inter- 

 mi diute spans equal to twice the tower spans; 60 feet and 30 feet, and 80 feet and 40 feet being 

 common lengths of span. 



Swing, movable, cantilever and suspension bridges will not be considered in this chapter. 



20 30 40 50 60 70 80 00 100 

 Span in Feet. 



50 100 150 WO 150 300 

 Span in Feet. 



IG. 3. WEIGHT OF SINGLE TRACK DECK 

 PLATE GIRDER SPANS, CONCRETE BALLAST 

 FLOOR. CHICAGO, MILWAUKEE & ST. 

 PAUL RY. 



FIG. 4. WEIGHT OF SINGLE TRACK RIVETED 

 DECK TRUSS SPANS. CHICAGO, MIL- 

 WAUKEE & ST. PAUL RY. 



WEIGHTS OF RAILWAY BRIDGES. The weights of railway bridges vary with the 

 loading, the specifications, the span, the width, the type of floor, and with the design. The weights 

 of the total structural steel in single track bridges of different types as designed and built by the 

 Chicago, Milwaukee & St. Paul Ry. are given in Fig. 3 to Fig. 10, inclusive. 



Weights of single track plate girder spans as designed and built by the Illinois Central Rail- 

 road are given in Fig. n, Fig. 12 and Fig. 13; weights of single track through bridges are given in 

 Fig. 14, weights of signal bridges are given in Fig. 15, and weights of single track draw spans are 

 given in Fig. 16. Weights and other data for railway bridges designed by the Harriman Lines, 

 under "Common Standard Specification 1006" (approximately equal to Cooper's E 55), are given 

 in Table I. 



Weights of single track steel viaducts as designed by the McClintic-Marshall Construction 

 Co. are given in Fig. 17. 



