Pony Truss 

 Bridges 



Plate Girders 



Compression 

 Flanges 



Fi an g e 

 Sections 



Web Plates 



Web Stiffeners 



64. Pony truss bridges shall be of the riveted type, they shall have double webbed 

 chords, and latticed or otherwise effectually stiffened web members. 



65. In all pony truss bridges, the vertical truss members and the floor beam connec- 

 tions shall be proportioned to resist, in addition to the stresses already specified, a lateral 

 force at the centre of gravity of the top chord of the truss not less than three per cent. 

 of the maximum axial stress at that point. 



66. Plate girders shall be proportioned either by their moment of inertia, using the 

 net section of both flanges and web, or by assuming that the flanges are concentrated 

 at their centres of gravity. In the latter case, 1/8 of the gross section of the web, if 

 properly spliced, may be used as flange section. For girders having unusual sections, 

 the moment of inertia method shall be used. 



67. The gross area of the compression flange of plate girders shall be not less than 

 the gross area of the tension flange, and further, the stress per square inch shall not 

 exceed : 



16 000 - 200-r-pounds, 



in which 



/ = the length of the unsupported flange, between lateral connections or knee 



braces, in inches. 

 6 = the flange width, in inches. 



68. Where flange cover plates are used, one cover plate on the top flange of through 

 plate girders shall extend full length, and unless otherwise specified by the Engineer, all 

 cover plates on the top flanges of deck plate girders shall extend full length (except where 

 side cover plates are used in compound flanges). Other cover plates (including side 

 covers in compound flanges) shall extend at least 18 inches beyond the theoretical point 

 at each end. 



69. The flange angles shall form as large a part of the area of the flange as practic- 

 able. Side plates shall not be used except when flange angles exceeding one inch in 

 thickness would otherwise be required. 



70. Flange cover plates shall be equal in thickness, or shall diminish in thickness 

 from the flange angles outward. No plate shall have a thickness greater than that of 

 the flange angles. 



7lA. Splices in flange members of plate girders, when not shown on the Railway 

 Company's drawings, shall not be used except by special permission of the Engineer. 

 Two members in any one flange shall not be spliced at the same cross section, and, if 

 practicable, splices shall be located at points where there is an excess of material. Flange 

 angle splices shall consist of angles. 



72. Web plates shall be so proportioned that the permissible shear on their gross 

 section will not be exceeded. Splices in web plates shall be avoided as far as possible, 

 but, when necessary, they shall be designed so that the full value of the web plate will be 

 uniformly developed, both for bending and for shear. 



73. Plate girders shall have stiffener angles over end bearings, the outstanding legs 

 of which shall extend as nearly as practicable to the outer edge of the flange angles. The 

 end stiffeners shall be proportioned for bearing of the outstanding legs, which shall be 

 arranged to transmit the end reaction to and distribute it over the pier members. 

 They shall be connected to the web by enough rivets to transmit the reaction. End 

 stiffeners shall not be crimped. 



74. The webs of plate girders shall be stiffened by angles at intervals not greater 

 than : 



(a) 6 'feet. 



(b) The depth of the web. 



