EIVETED JOINTS 15 



Let s t = ultimate tensile unit-stress of the plate, 

 let s c = ultimate compressive unit-stress of the rivets, 

 let s s = ultimate shearing unit-stress of the rivets. 



The efficiency of a joint is the ratio between the strength of the 

 joint and the strength of the unriveted plate. Consider a single- 

 riveted lap joint. In a repeating section there is here one rivet to be 

 compressed, one rivet area to be sheared, and the plate is weakened 

 by one rivet hole ; hence 



pts t = strength of unriveted plate, 



(p d)ts t = strength of riveted plate, (A) 



tds c = compressive strength of rivet, 



s s = shearing strength of rivet. 



It is evident that the strength of the repeating section will be repre- 

 sented by the least value obtained from these. 



We may compute three efficiencies from these expressions, but the 

 smallest one only will give the true efficiency of the joint. 



Or consider the following expressions. If the joint is so propor- 

 tioned that it would fail by the tearing of the plate between the 



holes, efficiency would be - - , 



P 



ds 

 or if by the compression of the rivets, efficiency would be ; (B) 



P s t 



or if by the shearing of the rivets, efficiency would be -- 



pts t 



We may therefore compute the efficiency of a joint in two ways : 

 by dividing the smallest value found from equations (A), by the 

 strength of the unriveted plate, or by the use of expressions (J5), where 

 the real efficiency of the joint will be the smallest one of the values 

 thus obtained. 



In a repeating section of a staggered double-riveted lap joint there 

 are two rivets to transfer the tension ; hence 



