SPECIFICATIONS 



403 



67. All rods with screw ends except sag rods must be 

 upset at the ends so that the diameter at the base of the 

 threads shall be 1-16 inch larger than any part of the body of 

 the bar. 



68. Upper chords shall have symmetrical cross-sections, 

 and shall preferably consist of two angles back to "back. 



69. All other compression members except sub-struts 

 shall be composed of sections symmetrically placed. Sub-struts 

 may consist of a single section. 



70. Side posts which take flexure shall preferably be com- 

 posed of 4 angles laced, or 4 angles and a plate. Where side 

 posts do not take flexure and carry heavy loads they shall pref- 

 erably be composed of two channels laced. 



Posts in end framing shall preferably be composed of I 

 beams or 4 angles laced. Corner columns shall preferably be 

 composed of one angle. 



The cross-bending stress due to eccentric loading in col- 

 umns carrying cranes shall be calculated. 



71. Laced compression members shall be stayed at the 

 ends by batten plates placed as near the end of the member as 

 practicable and having a length not less than the greatest width 

 of the member. The thickness of batten plates must not be 

 less than 1-40 of the distance between rivet lines at right angles 

 to axis of member. 



72. Single lattice bars shall have a thickness of not less 

 than 1-40, and double bars connected by a rivet at the intersec- 

 tion of not less than 1-60 of the distance between the rivets 

 connecting them to the member ; they shall make an angle not 

 less than 45 with the axis of the member; their width shall 

 be in accordance with the following standards, generally : 



SIZE OF MEMBER. 

 For 15-inch channels, or built 

 sections with 3^ and 4- 

 inch angles. 



For 12, 10 and 9-inch chan- 

 nels, or built sections with 

 3-inch angles. 



WIDTH OF LACING BARS. 



2^2 inches (J^-inch rivets). 



2)4 inches (^4 -inch rivets). 



Upset Rods. 



Upper Chords. 



Compression 

 Members. 



Columns. 



Crane Posts. 



Lacing. 



