
Reg. 177
SHELLS
Methods of calculating the strength of riveted joints
a) 
The percentage of strength
of a riveted joint (J) shall be found from the following
formulae (i), (ii), (iii); (i) and (ii) are applicable
to any ordinary type of joint, (iii) is applicable only
to that type of joint in which the number of rivets in
the inner rows is double that of the outer row. The lowest
value given by the application of these formulae is to
be taken as the percentage of strength of the joint compared
with the solid plate.
(i) 
100(P  D) 
= Plate percentage 
Eqn.(2). 
P 
(ii) 
100 x A x N x C x S1

= Rivet percentage 
Eqn.(3) 
P x T x S 
(iii) 
100(P  2D)

+ 
100 x A x C x S1 
= Combined
plate and rivet percentage . 
Eqn.(4) 
P 
P x T x S 
Where
P is the pitch of rivets of outer row in inches.
D is the diameter of rivet holes in inches.
A is the sectional area of one rivet hole in square inches.
N is the number of rivets per pitch (P).
T is the thickness of plate in inches.
C = 1 for rivets in single shear as in lap joints, and
1.875 for rivets in double shear as in double butt strapped
joints.
S1 is the shearing strength of rivets which shall be taken
to be 23 tons per square inch for steel and 18 tons per
square inch for iron.
S is the minimum tensile breaking strength of shell plates
in tons per square inch, or whatever strength is allowed
under Regulation 5
of chapter I,
In the first formula (i) D is the diameter of the rivet
holes in the outer rows and in the third formula D is
the diameter of the rivet holes in the next rows. In the
last formula A is the area of one rivet hole in the outer
row 
b) 
When the sectional area of
the rivet holes is not the same in all rows, and when
some of the rivets are in double shear and others in single
shear the rivet sections per pitch of each size in shear
shall be computed separately and added together to form
the total rivet section. 

