COOPER'S LOADINGS. 



153 



Cooper's Conventional System of Wheel Concentrations. In Cooper's loadings two con- 

 locomotives are followed by a uniformly distributed train load. The typical loading 

 for Cooper's Class 40, 45, E 50, E 55 and E 60, are shown in Fig. 18. The loads on the 

 (Irivi-rs in thousands of pounds and the uniform train load in hundreds of pounds are the same as 

 the class number. The wheel spacings are the same for all classes. The stresses for Cooper's 

 loadings calculated for one class may be used to obtain the stresses due to any other class loading. 

 For example, the live load stresses in any truss due to Cooper's Class E 60 are equal to f of the 

 stresses in the same truss due to Class E 40 loading. The E 50, E 55 and E 60 loadings are those 

 most used for steam railways in the United States. In bridges designed for Class E 40 loading 

 and under the floor system must in addition be designed for two moving loads of 100,000 Ib. each, 

 spaced 6 ft. apart on each track. The special loads for Class E 50 are 120,000 Ib. with the same 



ZO 30 40 50 60 70 80 90 100 

 Span in Feet. 



IG. 7. WEIGHT OF SINGLE TRACK DECK 

 .ATE GIRDER SPANS. OPEN TIMBER FLOOR. 

 TYPE A4 (FLANGES OF 6 ANGLES WITH- 

 OUT COVER PLATES). CHICAGO, MIL- 

 WAUKEE & ST. PAUL RY. 



ZO 20 40 50 00 70 80 90 100 

 Span in Feet. 



FIG. 8. WEIGHT OF SINGLE TRACK DECK 



PLATE GIRDER SPANS. TIMBER BALLAST 



FLOOR. TYPE A4 (FLANGES OF 6 ANGLES 



WITHOUT COVER PLATES). CHICAGO, 



MILWAUKEE & ST. PAUL RY. 



spacing. The American Railway Engineering Association has adopted Cooper's loadings, except 

 that the special loads are spaced 7 ft. The live loads used by several prominent railroads are 

 given in Table XVI. The heaviest locomotives in use on American railroads as given in Bulletin 

 No. 161, November 1913, of the Am. Ry. Eng.Assoc., by Mr. ]. E. Greiner, Consulting Engineer, 

 are given in Table II. The maximum stresses in terms of the maximum stresses for E 50 loading 

 for spans between 100 ft. and 10 ft. are given in the last two columns. The ratios for spans 

 greater than 100 ft. are less than for those given. The larger ratio is for short spans so that by 

 increasing the special concentrated loads a bridge designed for an E 50 loading will safely carry 

 the heaviest engines now in use. 



