eyes tre 
joint iy give way (1) by tearing at 
-E. The values of these various resistances 
a oe ee eee = Vig 
SIMPLE STRAINS AND STRESSES 75 
_ Fig. 85 shows a tie-bar joint. Here a bar of width } and thick- 
ness ¢ has a lap joint in it containing 
nine ened arranged as shown. This AB ¢. DE 
A or E; (2) by shearing of: all the 
rivets; (3) by tearing at B or D, and shear- 
ing at A or E; (4) by tearing at C, 
and shearing at A and B or at D and 
ae ee 
are— Fra. 85 
i aif... +... a..(2) (b-2dVifi+70h, « ADF OA 6) 
Mf.» QB) . O-3t3sTTy. . . . - 
The strength of the solid bar is bt/,, and the various efficiencies are 
ape stl har try ae APSR 
ae sebiidstas pd On sone Hata 64) 
There is only one dimension to determine, viz. d, and a value of d 
may be found by equating any two of the four expressions which give 
the resistance of the joint. Six possible values of d may be found in 
this way, but generally there is only one value which will give the highest 
minimum efficiency of joint. 
The most satisfactory way of finding the best value of d is to plot the 
various efficiencies for different values of d, as shown in Fig. 86. In this 
case } has been taken equal 
to 10 inches, t=1 inch, and 2100 (2) 
f,=0°8f,. The best diameterof & bec 4) 
rivet must be under the inter- $ 90 = 4 
section of a pair of efficiency a eae’ RAL aoe Cae (3 
curves, and an inspection of Re 7 
the figure shows that the dia- vi 
meter which gives the best S 
efficiency is under the inter- “705——~—75 16 18 
section of (2) and (3). This Dirvisten “of deas 
diameter is 1°23 inches, and Fic? 86 
the minimum efficiency is 85-6 ee 
per cent. In plotting the efficiency curves it is only necessary to show 
the : ahah in the neighbourhood of their intersections. 
butt joint with two cover straps, such as is shown in Fig. 87, is a 
more satisfactory joint for a tie-bar than the 
lap joint, because in the case of the butt joint ° i = 
the pulling forces on opposite sides of the 
joint are in the same plane, whereas in the ele 
case of the lap joint the pulling forces are in Oe ga ea 
different planes, and in consequence there is ae 
a bending action on the bar in the neigh- 
bourhood of the joint. 
