SPECIFICATIONS. 61 



87. Web Stiffeners. Web stiffeners shall be in pairs, and shall have a close fit against flange 

 angles. The stiffeners at the ends of plate girders shall have filler plates. Intermediate stiffeners 

 may have fillers or be crimped over the flange angles. The rivet pitch in stiffeners shall not be 

 greater than 5 in. 



88. Web Splices. Web plates shall be spliced at all points by a plate on each side of the 

 wi-li, capable of transmitting the shearing and bending stresses through the splice rivets. 



89. Net Sections. Net sections must be used in calculating tension members and in deducting 

 the rivet holes they shall be taken i in. larger than the nominal size of rivet. 



90. Pin connected riveted tension members shall have a net section through the pin hole 

 25 per cent in excess of the required net section of the member. The net section back of the 

 pin hole in line of the center of the pin shall be at least 0.75 of the net section through the pin 

 hole. 



91. Upset Rods. 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 & inch larger than any part of the body of the bar. 



92. Upper Chords. Upper chords of trusses shall have symmetrical cross-sections, and shall 

 preferably consist of two angles back to back. 



93. Compression Members. All other compression members for roof trusses, except sub- 

 struts, shall be composed of sections symmetrically placed. Sub-struts may consist of a single 

 section. 



94. Columns. Side posts which take flexure shall preferably be composed of 4 angles laced, 

 or 4 angles and a plate. Where side posts do not take flexure and carry heavy loads they shall 

 preferably be composed of two channels laced, or of two channels with a center diaphragm. 



95. Posts in end framing shall preferably be composed of I-beams or 4 angles laced. Corner 

 columns shall preferably be composed of one angle. 



96. Crane Posts. The cross-bending stress due to eccentric loading in columns carrying 

 cranes shall be calculated. Crane girders carrying heavy cranes shall be carried on independent 

 columns. 



97. Batten Plates. 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 shall not be less than -fa of the 

 distance between rivet lines at right angles to axis of member. 



98. Lacing. Single lacing bars shall have a thickness of not less than fa, and double bars 

 connected by a rivet at the intersection of not less than fa of the distance between the rivets 

 connecting them to the member; they shall make an angle not less than 45 degrees with the axis 



the member; their width shall be in accordance with the following standards, generally: 



Size of Member. . Width of Lacing Bare. 



For 15 in. channels, or built sections with 3$ and 4 in. angles.. .2j inches (| in. rivets). 

 For 12, 10 and 9 in. channels, or built sections with 3 in. angles. . .2} inches (J in. rivets). 

 For 8 and 7 in. channels, or built sections with 2\ in. angles.. . .2 inches (f in. rivets). 

 For 6 and 5 in. channels, or built sections with 2 in. angles i \ inches (i in. rivets). 



I Where laced members are subjected to bending, the size of lacing bars or angles shall be cal- 

 lated, or a solid web plate shall be used. 

 99. Pin Plates. All pin holes shall be reinforced by additional material when necessary, so 

 as not to exceed the allowable pressure on the pins. These reinforcing plates must contain enough 

 rivets to transfer the proportion of pressure which comes upon them, and at least one plate on 

 each side shall extend not less than 6 in. beyond the edge of the batten plate. 



100. Maximum Length of Compression Members. No compression member shall have a 

 length exceeding 125 times its least radius of gyration for main members, nor 150 times its least 

 radius of gyration for laterals and sub-members. The length of a main tension member in which 

 the stress is reversed by wind shall not exceed 150 times its least radius of gyration. 



101. Maximum Length of Tension Members. The length of riveted tension members^ in 

 horizontal or inclined position shall not exceed 200 times their radius of gyration except for wind 

 bracing, which members may have a length equal to 250 times the least radius of gyration. The 

 horizontal projection of the unsupported portion of the member is to be considered the effective 

 length. 



102. Splices. In compression members joints with abutting faces planed shall be placed as 

 near the panel points as possible, and must be spliced on all sides with at least two rows of rivrts 

 on each side of the joint. Joints with abutting faces not planed must be fully spliced. 



103. Splices. Joints in tension members shall be fully spliced. 



104. Tension Members. Tension members shall preferably be composed of angles 

 shapes capable of taking compression as well as tension. Flats riveted at the ends shall not I 

 used. 



