PLATE GIRDERS 41 



at the ends and inner edges of bearings and at points of concen- 

 trated loads, their area to be determined by the formula: 



S = 16,000 -70-, 



where S = allowable unit stress. 



I = one-half the depth of girder in inches. 

 r= Radius of gyration of angles, neglecting fillers and 

 inclosed portion of web. 



End stiffeners, those under concentrated loads and at web splices, 

 shall be on fillers and have their outstanding legs as wide as the 

 flange angles will allow and shall fit tightly against them. 



Where the thickness of the web is less than one-sixty-fourth 

 (fa) of its depth between inner rivet lines intermediate stiffeners 

 shall be used. 



The intermediate stiffeners shall be spaced by the formula: 



For girders in buildings d^64t( -~ ) . 



\ v / 



(1 2000X 

 ~~o ) ' 



where d= distance in inches between centers of stiffeners, with a 

 maximum distance equal to the depth of the girder, or 

 64 in. 



t= thickness of web in inches; 

 Q = shear in web per square inch. 



Intermediate stiffeners may be offset (crimped), and their out- 

 standing legs shall not be less than one-thirty-second (fa) of the 

 depth of the girder plus 2 in. 



1 68. Bracing. All deck-plate girder bridges shall have lat- 

 eral bracing near the plane of the top chord, but far enough 

 below the flanges to clear the ties, and those having a span of 

 ft. or over shall in addition have lateral bracing in the plane 

 of the bottom chord. Cross frames shall be located near each 

 end and at intermediate points not exceeding 20 ft. The lateral 

 system shall generally be of the single cancellation type. 



Through-plate girder spans, not having a solid floor, shall 



