32 
thickness of met 
al. 
lates^ " '^ ^ ^ *^ Gusset OF coDiiecting plates shall be used for connecting 
all main members, except in pin-connected structures. 
In proportioning and detailing these plates the rivets 
connecting each member shall be located, as nearly as 
practicable, symmetrically with the axis of the member. 
However, the full development of the elements of the 
member shall be given due consideration. The gusset 
plates shall be of ample thickness to resist shear, direct 
stress, and flexure acting on the weakest or critical section 
of maximum stress. 
Reentrant cuts shall be avoided as far as possible. 
27. Minimum xiie minimum thickness of structural steel shall be ^ 
inch except for fillers and railings. However, gusset 
plates shall not be less than % inch in thickness. 
Metal subjected to marked corrosive influence shall be 
increased in thickness. 
Cast steel shall not be less than 1 inch and cast iron 
not less than 134 inches thick, except for filler blocks. 
In built compression members the metal shall be con- 
centrated as much as possible in the webs and flanges, so 
that the center of gravity of the section m.ay be as near 
the center line of the member as practicable. 
Cover plates of built compression members and cover 
plates on the compression flanges of plate girdere shall 
have a minimum thickness of one-fortieth, and the web 
plates of compression members a minimum thickness of 
one-thirtieth of the transverse distance between the lines 
of rivets connecting them to the flanges. However, fail- 
ing to meet this requirement, the width of plate between 
the connecting lines of rivets in excess of 40 times the 
thickness of cover plates and 30 times the thickness for 
web plates shall not be considered as effective in resisting 
stress. 
Outstanding compression flanges of girders and main 
compression members shall have a minimum thickness 
of one-twelfth of the width of the outstanding flange. 
For lateral bracing and other secondary members this 
minimum thickness may be one-fourteenth of the widtb 
of the outstanding flange. 
The open sides of compression members shall be pro- 
vided with lacing bars and shall have tie-plates as near 
each end as practicable and at intermediate points where 
the lacing is interrupted. Compression members com- 
posed of two angles and a cover plate shall have, on their 
open sides, tics composed of short lengths of channel sec- 
tion with the flanges riveted to the vertical leo:s of the 
28. Compres- 
ion members. 
29. Plates 
compression 
30. Outstand 
ing flanges. 
31. Tie-plates. 
Tension members composed of shapes shall have their 
separate segments connected by tie-plates or by tie- 
plates and lacing bars. 
The thickness of the tie-plates shall be not less than 
one-fiftieth of the distance between the connecting lines 
of rivets. Tie-plates shall be connected by not less than 
three rivets on each side and in members having lacing 
