SPECIFICATIONS FOR STEEL HIGHWAY BRIDGES. 33 
bars the last rivet in the tie-plate shall preferably also 
pass through the end of the adjacent bar. 
For main compression members the end tie-plates 
shall have a length not less than l}^ times the perpen- 
dicular distance between the lines of rivets connecting 
them to the member and the intermediate tie-plates a 
length not less than that distance. For main tension 
members the end tie-plates shall have the length above 
specified for end tie-plates on main compression members 
and the length of the intermediate tie-plates shall be not 
less than three-fourths the length specified for inter- 
mediate tie-plates on compression members. In ten- 
sion members whose elements are connected by tie- 
plates only, the distance center to center of plates shall 
not exceed 3 feet. 
For lateral struts and other secondary members the 
length of end and intermediate tie-plates shall be not 
less than three-fourths the perpendicular distance be- 
tween the lines of rivets connecting them to the member. 
The lacing of compression members shall be propor- ^2. Lacing bars 
tioned to resist a transverse shear not less than that cal- 
culated by the formula : 
S = 300A. 
where 
S -= transverse shear in poimds. 
J. = gross area of member in square inches. 
This shear shall be considered as divided equally among 
all stifl'ening parts in parallel planes, whether made up 
of continuous plates or of lattice. The stress in the in- 
dividual lacing bar shall be taken as the component of the 
the shear, in the direction of the bar, in case single lacing 
is used and half that amount if double lacing is used. 
The size of the bar shall be determined by the column 
formula in which ^^L" shall be taken as the distance 
between the connections to the main sections. 
The minimum mdth of lacing bars shall be: 
For J/g-mch. rivets, 23^2 inches. 
For ^-inch rivets, 23^ inches. 
For ^-inch rivets, 2 inches. 
Lacing bars having two rivets in each end shall be 
used for flanges 5 inches or more in width. 
The minimum thickness of bars shall be one-fortieth of 
the distance between end rivets in the case of single lac- 
ing and one-sixtieth of this distance for double lacing. 
Double lacing, riveted at the intersections, shall be 
used when the perpendicular distance between rivet 
lines exceeds 15 inches. 
The inclination of single lacing shall generally be about 
60 degrees, and for double lacmg it shall be about 45 
degrees to the axis of the member. Furthermore, the 
maximum spacing of lacing bars shall be such that the 
ratio of length to radius of gyration ( — jfor the portion of 
