30 STANDARD SPECIFICATIONS 



tenth (fo) of the span. Plate girders and rolled beams, used 

 as girders, shall preferably have a depth of not less than one- 

 twelfth ( T y of the span. If shallower trusses, girders, or beams 

 be used the section shall be increased so that the maximum deflec- 

 tion will not be greater than if the above limiting ratios had not 

 been exceeded. 



For general dimensions see Par. 75. 



126. Floor Framing. Stringers shall preferably be riveted 

 to the webs of all intermediate floor beams by means of connection 

 angles not less than ^ in. thick. Shelf angles, or other means 

 provided to support the stringers during erection, shall not be 

 considered as carrying any of the reaction. 



Floor beams shall preferably be arranged so as to be perpendic- 

 ular to the girder or truss at the panel point, they may rest upon 

 the top chord in deck bridges, but in through bridges they shall 

 be riveted to the verticals. 



\Yhere end floor beams are not used stringers resting on 

 masonry shall have cross frames near their ends. These frames 

 shall be riveted to girder or truss shoes where practicable. (Par. 

 129.) 



127. Beam and Plate-Girder Bridges. (See Pars. 79, 125, and 

 Part IV.) 



128. Pony Bridges. Pony trusses shall be riveted structures 

 with double-webbed chords and shall have all web members 

 latticed or otherwise effectively stiffened. (Par. 80.) 



129. Deck Bridges. Deck spans shall have transverse brac- 

 ing at each end proportioned to carry the lateral load to the 

 supports. (Par. 81.) 



130. Through Bridges. All trusses shall be so designed 

 that the stresses may be determined with reasonable accuracy. 



The hip verticals and similar members, and the two end panels 

 of the bottom chords of all single-track pin-connected trusses, 

 and of all double-track trusses over 300 ft. span, shall be made 

 rigid. 



Rigid counters are preferred, and where subject to reversal 

 of stress shall preferably have riveted connections to the chords. 

 Adjustable counters shall have open turnbuckles. 

 131. Bracing. Lateral, longitudinal, and transverse bracing 

 in all structures shall be composed of rigid members. 



Through truss spans shall have riveted portals which shall be 



