DESIGN OF STRUCTURES 213 
uare foot, One end of the truss is to be firmly bolted down, and 
capable of sliding. Rolled steel sections only to be used, with 
; ign a queen-rod roof truss with vertical struts of the form and 
nsions shown in Fig. 301. Distance apart of principals, 10 feet. Take the 
dead weight of the roof as 20 lbs. per 
ure foot, horizontal wind pressure as 50 
DS. per square foot, and snow as 6 lbs. per 
are foot. One end of the truss to be free 
, 
is 100 feet. The total rise is 25 feet, and the bottom chord has a rise of 
ie There are eight equal segments in the top chord, and seven equal 
_ Segments in the bottom chord. The trusses are 20 feet apart. Take the dead 
load as 18 lbs. per square foot. Snow, 6 lbs, per square foot. Horizontal wind 
cepeche 50 Ibs. per square foot. One end of the truss is bolted down, and 
__ the other slides. Use rolled steel sections only. 
7. The principals of a steel'roof for a dock shed are of the form sketched in 
Fig. 302. The rafters are 
- equally divided at the joints, 
- and a vertical load of 1} 
tons acts at each top joint. 
_ The huge ary are sup- 
ported on girders 8 inches 
wide, Draw the force dia- 
og the roof, and 
q your results, dis- 
peptishing between ties 
and struts. Design also Fic. 302. 
the joints at A and B. % 
a our own stresses, and draw the details one-quarter full size. [U.L. 
__ 8. The tie rod of a roof truss is connected to the foot by two clip plates, an 
_ by a cotter joint with two gibs. The diameter of the tie rod is 1} inches, 
R this joint for equal 
_ strength throughout. The forte eee ne---> 
type of joint is indicated in (~ — 
hpeketch (Fig. 303). Draw, § & cS ©pP PE pees. «2 
_ full size, plan and elevation, >. 
_ and any necessary sections. 
_ The drawings must be fully Fria. 303. 
dimensioned and finished 
off neatly in pencil. All calculations must be fully worked out, and must be 
_ handed in with your drawings. (U.L.] 
