COMPARISON OF RAILWAY BRIDGE SPECIFICATIONS. 207 



79. Web Stiffeners. Seven specifications have the same specification as given in section 79- 

 Two >|K (itir.it ion> require that stiffeners be spaced not to exceed depth of girder. The Baltimore 



The New York Central Lines require that stiffeners be spaced not to exceed depth of 

 h r or ft. 6 in.; near ends of girders the spacing shall not exceed one-half the depth of girder 

 or .} ft. 6 in. 



The New York Central Lines require that stiffeners shall have an outstanding leg not less 

 than 2 inches plus 5^ the depth of the girder. 



The Chicago, Milwaukee & St. Paul Ry. requires that stiffeners bearing against 6" X 6" 



flange angles shall be 5" X 3*" X f"; and against 8" X 8" flange angles shall be 6" X 3*" X |". 



8 1. Camber of Trusses. Six specifications require full camber as stated in section 81. Six 



specifications require that the upper chords be increased J in. for each 10 ft. One specification 



requires that the upper chord be increased i in. for each 15 ft. Two specifications require that 



a be cambered TW the span. One specification requires that trusses be cambered rfco the 



span. 



82. Rigid Members. All specifications require that hip verticals and the two end panels 

 of bottom chords (two at each end) be stiff members. The Common Standard specifications 

 (Harriman Lines) require that the bottom chords of bridges of less than 150 ft. span be stiff 

 members. The Illinois Central R. R. requires that bridges with 6 panels or less shall have stiff 

 lower chords. The New York Central Lines limit the specification for rigid members to spans 

 less than 300 ft. 



83. Eye-bars. Nine specifications permit bars to be out of line i in. in 16 ft. as in section 83. 

 le specification permits bars to be out of line I in. in 8 ft. 

 Miscellaneous. The following specifications are of interest. 



Initial Stress. Four of the sixteen specifications require that diagonals and struts be designed 

 for an initial stress of 10,000 Ib. in each diagonal. 



Collision Strut. Two of the sixteen specifications require collision struts. 

 Fastening Angles. Two specifications require that angles .must be fastened by both legs, 

 iree specifications require that angles be fastened by both legs or only one leg will be considered 

 fective. One specification requires that 75 per cent of the net area be considered effective where 

 igles are fastened by one leg, and 90 per cent of the net area be considered effective where angles 

 fastened by both legs. 



Calculating Dead Load Stresses. One specification requires that all the dead load be con- 

 sidered as coming on the loaded chord. Two specifications require that three-fourths of the dead 

 id be considered as coming on the loaded chord and one-fourth on the unloaded chord. Two 

 ecifications require that two-thirds of the dead load be considered as coming on the loaded chord 

 id one-third on the unloaded chord. Two specifications require that the floor load shall be 

 wumed as taken by the loaded chord, and the remainder of the dead load to be divided equally 

 jtween the chords. The other specifications do not state where the dead load shall be applied. 

 Minimum Bar. Three specifications require that the minimum bar shall have not less than 

 sq. in. cross section. One specification permits a minimum bar I } in. square. One specification 

 jquires that an increase of 80 per cent in the live load shall not increase the stress in the counters 

 lore than 80 per cent. One specification has a similar clause with 70 per cent variation. 

 Paint. The shop coat of paint as required by several specifications is as follows: 

 The New York Central Lines use red lead paint mixed by the following formula: too Ib. 

 sure red lead; 4 gallons pure open-kettle-boiled linseed oil; and not to exceed one-half pint of 

 irpentine-japan drier. 



The Boston & Maine R. R. and the New York, New Haven & Hartford R. R. use red lead 

 lint made by mixing 32 Ib. of red lead to one gallon of linseed oil. 



The A. T. & S. F. Ry. gives steel work a shop coat of linseed oil; while the C. R. I. & P. 

 1. R. uses linseed oil with 10 per cent of lamp black. 



The Illinois Central R. R. uses red lead paint for a shop coat. 



The Pennsylvania Lines West of Pittsburgh use a shop coat of pure linseed oil. 



The Common Standard specifications require a shop coat of red lead. 



