KIVETED JOINTS AND CONNECTIONS 149 



where k = 1.5 for lap joints and k = 1.3 for butt joints with two 

 cover plates. 



The pitch of the rivets is next determined by equating the strength 

 of the plate along a section through the rivet holes to the strength 

 of the rivets in shear and solving the resulting equation for c. 



To illustrate the application of these rules, let it be required to 

 design a boiler shell 48 in. in diameter to carry a steam pressure of 

 125 lb./in. 2 with a double-riveted, double-strapped butt joint. 



By the above rule for thickness of shell plates we have 



125 x - 4 8 - 



h = 



eoooo 



5 



The diameter of rivets is then 



d = 1.3 ^/~J1 = .73, say | in. 



To determine the pitch of the rivets, the strength of the plate for 

 a section of width c on a line through the rivet holes is 



(cd)hp = (c \)^ X 60,000, 

 and the strength of the rivets in shear for a strip of this width is 



4x^0 = 71-:^ x 40,000. 

 4 16 



Equating these two results and solving for c, we have 



(c _ |) _5_ x 60,000 = TT T 9 g x 40,000, 

 whence c = 4.5 in. 



As a check on the correctness of our assumptions the efficiency of 

 the joint is found to be 



c-d 4.5 -.75 



e = 



4.5 



QQ 

 = .00. 



92. Structural steel. For bridge and structural work the following 

 empirical rules are representative of American practice : * 



The pitch (or distance from center to center) of rivets should not 

 be less than 3 diameters of the rivet. In bridge work the pitch 

 should not exceed 6 in. or 16 times the thickness of the thinnest 



* Given by Cambria Steel Co. 



