STRESS DIAGRAMS 199 
wise, the magnitudes of the unknown forces X, Y, Z, and deduce the force in 
‘the member AB. [U.L.] 
x 
; 6-7" 
LU er 
5 >. , b 
”) 
iS 
50° 
o 3 
Fig. 270. > - Fie. 271. 
40. In the truss shown (Fig. 271), AB is a beam member. The links AE, EG, 
_ GF, and FB are equal, and the links EC and FD connect the joints E and ¥F to 
4 The span 
_ of the frame given 
in Fig. 272 is 57 
feet, the depth 
_ LM is 7 feet, and et |M 
the distance NO is Wa. 272 
18 feet. There Aare 
are loads of 2 tons at P, 4 tons at O, and 2 tons at M. Find the stresses in the 
_ members. [U.L.] 
12. A truss is as shown in Fig. 273. 
Each top joint carries a load W, and 
the top boom is divided into equal 
' segments. The length of the horizon- © 
= age is helt ee oe Deter- 
mine the ratio of depth to span so : 
that the tension in all the tie-rods Fig, 378. 
shall be the same, and prs your result by drawing a force diagram. [U.L.] 
13. The sketch (Fig. 274) shows the frame of a tandem bicycle. Calculate 
120 lbs. 120 lbs. 
Se eens ee gS Soe 
| ne 30 lbs. 30 lbs. ' 
be — 5 23~ - — --10™ He -12~ te -10* 9" >! 
Fia. 274. 
. and draw bending moment and shear diagrams for this frame, when each of the 
__ two riders weighs 150 Ibs., 30 Ibs. of the weight of each rider being assumed to 
____ be borne at the driving axle centres. Regarding the frame as a plane structure, 
draw a complete force diagram for it. [B.E.] 
td 
