12 



PROBLEMS IN STRENGTH OF MATERIALS 



IV. RIVETED JOINTS . 



In structural work, as in girders, trusses, etc., and in many forms 

 of receptacles, such as tanks, the shells of steam boilers, etc., composed 

 of plates, the plates are joined together by riveted joints. 



When the plates are in tension the rivets transfer the tension 

 from one plate to another. This brings a stress upon each rivet, 

 which tends to shear it across in the plane of the surfaces of con- 

 tact of the plates. A compressive stress is also brought upon the 

 rounded surface of the rivet, where it bears upon the plate, which 

 tends to crush it against the metal of the plate hi front of the rivet. 

 This is called a bearing stress, and the exact manner in which this 

 stress acts between the cylindrical surface of the rivet and the hole 

 in the plate through which the rivet passes is not known. Experi- 

 ment and experience, however, show that for our computations we 

 may suppose this stress to be uniformly distributed over an area 

 which is the projection of the curved surface of the rivet hole up 

 on a plane through its axis. We then compute for this projected 

 area a working unit-stress whose safe value has been determined by 

 experiment. 



The general discussion of riveted joints covers their use in all kinds 

 of structures, but we shall limit our attention to their use in uniting 

 plates of pipes and shells which are subjected to internal fluid pres- 

 sure, and have to be designed for tightness as well as strength. The 

 special case is that of cylindrical boiler shells. 



In connecting the plates, the rivets may be arranged in many dif- 

 ferent ways, but in general they are distributed in rows extending 

 parallel to the edges of the plates that are joined, as is shown in the 

 diagrams of a few forms of joints (see Figs. 39). 



r- -T_ 



r-J-*i "1 ) 



FIG. 3. Single-Riveted Lap Joint 



FIG. 4. Double-Chain-Riveted Lap Joint 



