HIGHWAY BRIDGES 23 



to the floor beams and the floor beams to the trusses shall be 

 increased by 25 per cent. 



Where sidewalks are placed outside the trusses, and supported 

 on brackets, the connection shall preferably be made by means 

 of a fully riveted tension plate, as no tension on rivet heads will 

 be allowed. 



90. Riveted Work. In riveted work the main members shall 

 be arranged, wherever practicable, so that the effective sectional 

 area is placed symmetrically about the two principal neutral 

 axes. (Par. 88.) 



Where two connected members have their centers of gravity 

 in a continuous line the rivets in the splice plates must be arranged 

 symmetrically about these, using the minimum pitch (Par. 34), 

 and, by staggering or otherwise, have as few rivets as possible 

 in planes parallel and perpendicular to the axis of the member. 



Where two members are connected by means of gusset plates 

 the rivets must be arranged symetrically about both inter- 

 secting center lines of gravity. 



The secondary stresses due to non-compliance with these rules 

 must be provided for in the joint by increasing the area of splice 

 or gusset plates and the number of rivets, or both. 



91. Rivet Spacing. (See Par. 34.) 



92. Edge Distance of Rivets. (See Par. 35.) 



93. Tension Members. In calculating the net area of tension 

 members the area of rivet holes must be deducted, assuming 

 the diameter of the hole J in. larger than the nominal size of the 

 rivet. 



Main tension members shall be composed of sections placed 

 symmetrically about the central plane through the truss. Sec- 

 ondary tension members may be made of a single shape. (Par. 

 72.) 



Pin-connected riveted tension members shall have a net 

 section through the pin hole 25 per cent in excess of that through 

 the body of the main member. The minimum net section back 

 of the pin hole, parallel to the axis of the member, shall not be 

 less than that through the body of the main member. 



94. Eye-bars. Heads of eye-bars shall be forged and so pro- 

 portioned as to develop the full strength of the bar. (Par. 

 43.) 



The eye-bars shall be placed in the truss so as to be, as nearly 



