RIVETED JOINTS AND CONNECTIONS 155 



260. Design a double-riveted butt joint to have an efficiency of 75 per cent, 

 using 1-in'. steel plates and steel rivets. 



Solution. For any strip along the joint of length equal to the pitch c, two rivets 

 are in double shear. Hence for equal strength in tension and shear we have 



Also ' ~c~ = e ' whence & = c(l e) and c d = ce. Hence, substituting these 

 values of c d and d in the first equation, the result is 



cehp = ire 2 (1 e) 2 q 



whence c = - ^ - = 4.586 in., 



7r(l-e) 2 g 



or say c = 4{j in. 



Then d = c(l-e) = 1.156, or say d = 1^\ in. 



From the results of problem 259 it is apparent that the crushing strength of the 

 joint need not be considered, since here d < 1.273 h. 



The butt straps should apparently each be half as thick as the plate, but when 

 so designed they are found to be the weakest part of the joint. It is therefore 

 customary to make the thickness of the butt straps about f ft, or, in the present 

 case, f in. 



261. In a double-riveted lap joint the plates are \ in. thick, rivets | in. in 

 diameter, and pitch 3 in. Calculate the efficiencies of the joint and determine 

 how it will fail. 



262. A boiler shell is to be 4 ft. in diameter, with double-riveted lap joints, and 

 is to carry a steam pressure of 90 lb./in. 2 with a factor of safety of 5. Determine 

 the thickness of shell plates and diameter and pitch of rivets. Also calculate the 

 efficiency of the joint. 



263. A cylindrical standpipe is 75 ft. high and 25 ft. inside diameter, with 

 double-riveted, two-strap butt joints. Determine the required thickness of plates 

 near the bottom for a factor of safety of 5, and also the diameter and pitch of rivets. 



264. A boiler shell f in. thick and 5 ft. in diameter has longitudinal, single- 

 riveted lap joints, with 1-in. rivets and 2^-in. rivet pitch. Calculate the maximum 

 steam pressure which can be used with a factor of safety of 5. 



265. A cylindrical standpipe 80 ft. high and 20 ft. inside diameter is made of 

 l-in. plates at the base, with longitudinal, single-riveted, two-strap butt joints, 

 connected by 1-in. rivets with a pitch of 3^ in. Compute the factor of safety when 

 the pipe is full of water. 



266. Determine the diameter and pitch of rivets required to give the strongest 

 single-riveted lap joint, using |-in. steel plates and steel rivets, and calculate the 

 efficiency of the joint. 



