HIGHWAY BRIDGES 21 



be provided with riveted or cast-iron separators spaced not 

 over 5 ft. 



80. Pony Bridges. The top chord of pony trusses shall be 

 securely stayed at each panel point by means of gusset plates, 

 knee braces, or wide web members of angles with lattice or web 

 plate when efficiently connected to the floor beams. 



81. Deck Bridges. Trusses in deck bridges shall be pro- 

 vided at each panel point in the bottom chord with vertical 

 sway bracing sufficiently strong to carry the lateral forces to 

 which they are subjected. 



82. Through Bridges. All trusses shall be so designed that 

 the stresses may be determined with reasonable accuracy; they 

 shall have stiff hip verticals, and in the bottom chord the two 

 end segments shall also be made rigid whenever the stresses 

 reverse or are near that point. 



All web members, including counters, except for long spans 

 (Pars. 50, 94, 95), shall be made rigid. 



83. Bracing. Ends of all through spans shall be provided 

 with portals of rigid design, which shall be as deep as the required 

 clearance (Par. 52) will allow, and in the end posts proper pro- 

 vision shall be made for the bending stresses produced by such 

 portals. 



All the intermediate panel points in the top chord of through 

 spans shall be provided with transverse struts with knee braces 

 or with vertical sway bracing. The struts shall be made of 

 four angles laced and shall have the same depth as the chord, 

 to the upper and lower face of which they shall be riveted by 

 means of connection plates. 



In the plane of the " loaded " chord ends of all bridges shall 

 be provided with lateral struts where no end floor beams are used. 



Lateral, longitudinal and transverse bracing in all structures 

 shall be composed of rigid members. 



84. Steel Trestles. Each trestle bent shall be composed of 

 two columns braced together and, when battered, the batter 

 shall generally not be less than 1 horizontal to 8 vertical or more 

 than 1 horizontal to 4 vertical. 



The majority of the bents shall be united in pairs, forming 

 a tower, which shall be rigidly braced on all four sides and shall 

 have four horizontal struts at its base. 



The column feet shall be secured to the foundations by means 



