192 PRACTICAL STRUCTURAL DESIGN 



the member. Looking in the table, in the column headed by 

 thickness of plate, opposite the size of rivet will be found the 

 bearing value. In the column headed by shear find the shearing 

 '^Mw^^^M^wn value of the rivet. Use the smaller 



^" ^-^ value. Divide the total load by 



this selected value and obtain the 



* i ^ ' f number of rivets. If the rivets 



are in double shear double the 

 shearing value given in the table 

 and compare it with the bearing 

 value, using the smaller amount. 

 The rivets selected in this way are 

 Double shear ga f e a g a i ns t destruction by shear- 



g- 112< ing across and the edges of the 



holes through the plate will not crush. Fig. 112 illustrates single 

 and double shear. 



Let / = bearing value on plate in Ibs. per sq. in. 

 i = thickness of plate in inches. 

 v = shearing value of rivet in Ibs. per sq. in. 

 d = diameter of rivet. 

 Then 



Shearing value in single shear = 0.7854 x d 2 X v. 



Shearing value in double shear = 2 x 0.7854 x d 2 X V. 



Bearing value = d x t x /. 



When driven, rivets are assumed to completely fill the holes, 

 and, therefore, in compression pieces no reduction in area is made 

 for the rivet holes. Tensile stress cannot, however, be trans- 

 mitted through the rivets and the area occupied by rivet holes 

 weakens the piece in tension. If the member is narrow and one 

 hole is drilled, or punched through it, the piece must be increased in 

 width or thickness to make up for the area removed by the hole. 

 Thus, if in a bar 4 ins. wide and \ in. thick a hole f in. diameter 

 is made, the bar will be increased in width by f in., or the thick- 

 ness will be increased, provided the width must be maintained. 

 The thickness is increased as follows: The width left is 3.25 ins. 

 The area removed is \ x f = f sq. in. The thickness to be added 

 equals 0.3750 -5- 3.25 = -fa in., making the total thickness f in. 

 There may be one hole through the plate or there may be several. 

 If the holes are in line the cross-sectional area of one hole is de- 

 ducted. If the holes are in two lines the cross-sectional area of 



