CHAPTER IV. 

 STEEL RAILWAY BRIDGES. 



TYPES OF STEEL BRIDGES. The same types of trusses are used for railway as for high- 

 way bridges, Fig. 4, Chapter III. Beam bridges are used for short spans, and plate girders up to 

 spans of about 125 ft. Riveted truss spans are used for spans of 100 ft. and upwards. Pin-con- 

 nected truss spans are still used for long span bridges and by a few railroads for spans of 150 ft. 

 and upwards. Many railroads are building riveted trusses for spans of more than 200 ft., and 

 riveted truss spans of 300 ft. are not uncommon. The new terminal bridge over the Missouri 

 River at Kansas City, Mo., has riveted trusses with a span of 425 ft. 6$ in. The Norfolk & West- 

 ern R. R. has constructed a double track bridge over the Ohio River with a span of 520 ft., which 

 is riveted with the exception of four bottom chord panel points, which have pin joints. The 

 lengths and types of railway bridges as used by different railroads are given in Table XII in the 

 latter part of this chapter. The longest simple truss span is 668 ft. and is in the Municipal Bridge 

 over the Mississippi River at St. Louis, Mo. The maximum practical length of simple span truss 

 bridges made of carbon steel is about 550 feet; while with nickel steel it is practical to build simple 

 truss spans up to 750 feet and economical to build simple truss spans up to 700 feet. The pro- 

 posed Metropolis Bridge over the Ohio River will be a double track simple truss bridge with a 

 in of 720 feet. 



Portal --, 



FIG. i. DIAGRAMMATIC SKETCH OF A RAILWAY TRUSS BRIDGE. 



149 



