SPECIFICATIONS FOE STEEL HIGHWAY BEIDOES. 
23 
Girders and truss members, except as noted below, g^J^^^^lJlJilsj^r 
shall be designed for the following uniform loads, ex-es. 
pressed in pounds per square foot of roadway width 
between curbs: 
Loaded length. 
Load.i 
Class 1-15 
Class 1-20. 
Class 2-15. 
Class 2-20. 
60 feet 
Pounds. 
100 
80 
60 
Pounds. 
130 
90 
70 
Pou nds. 
180 
120 
90 
lOOfeet 
200 feet and over 
J Proportionate loads shall be used for intermediate lengths. 
The lengths given are to be considered as loaded 
lengths and the uniform load used shall correspond to 
the length of that portion of the span which, when fully 
loaded, will produce maximum stress in the member 
under consideration. 
WJien the loaded length is less than 50 feet, girders and 
truss members shall be designed for the floor loads here- 
inafter specified. The trucks shall be so placed as to pro- 
duce the most severe stresses, but trucks in tandem need 
not be considered. When two lines of trafiic are to be 
considered the trucks shall be assumed to be running in 
the same direction. 
Sidewalk live loads shall be uniform loads of 80 pounds 8. side walk 
per square foot for loaded lengths of 50 feet or less, and^°^^^°^* 
60 pounds per square foot per loaded lenths of 100 feet 
or more. For intermediate lengths proportionate loads 
shall be used. All stringers and brackets of sidewalks 
shall be designed for not less than 80 pounds per square 
foot. 
Stringers, floor beams, and floor beam hangers shall be ^- ^loor loads, 
designed for the following loads. Furthermore, girders, 
trusses, and truss members in which the maximum live- 
load stresses result from loaded lengths of less than 50 
feet shall be so designed : 
Class 1-15. — One 15-ton truck, or 100 pounds per 
square foot of roadway, whichever produces the greater 
stress. 
Class 1-20.— One 20-ton truck. 
Cla^s 2-15. — Two 15-ton trucks. 
Class 2-20.~-Two 20-ton trucks. 
In bridges involving three or more lines of traffic the 
floorbeams and floorbeam hangers shall be designed for 
two trucks assumed to be located in the most unfavor- 
able position, together with a uniform live load of 100 
pounds per square foot on the width of roadway not 
occupied by the trucks. 
All live loads, except those due to centrifugal, tractive, lo. impact, 
and wind forces, shall be increased to their static equiv- 
alents by a proper allowance for dynamic, vibratory, 
and impact effects. The amount of this allowance or 
