filVETING. 



149 



Then 3.25 X 0.375 X 55> =7> 031 Ibs. = strength of 

 solid plate. 



(3.25 - 0.8125) X 0.375 X 55,000 = 50,273 Ibs. = 

 strength of net section plate. 



0.5185 X 3 X 38,000 = 59,109 Ibs. = strength of 3 rivets 

 in single shear. 



Net section of plate is weakest, therefore 50,273 -=- 67,031 

 = 75 per cent, efficiency of joint. 



FIG. 42. TklPLE- RIVETED JoiNT. 



Double-welt Butt-joint (Fig. 44). We now come to the 

 double-welt butt-joint, triple-riveted. 



I have selected this joint because we use it in practice where 

 boilers of large diameters and high pressures are required. 



In the double-welt joint a new element comes into the 

 problem, viz., that of rivets in double-shear. Its inner welt is 

 broader than the outer welt, and extends far enough beyond the 

 former to enable us to introduce a third row of rivets, which 

 are in single-shear, but also are in double-pitch. This in- 

 creases the net section of plate, and also adds another rivet to be 

 sheared. All the other rivets are in double-shear. The ques- 

 tion now arises, What is the value of a rivet in double-shear? 

 We have assumed, therefore, that the value of a rivet in 

 single-shear was 38,000 Ibs. per square inch. 



Now, can we assume that the same rivet in double-shear 

 has twice the value that it had in single-shear? It has been 



