Fig. 3241.
“Thus, [Fig. 3241] represents a single riveted lap joint, in which the joint at rivets a, b, and c is intact, the metal outside of d has crushed, the rivets e, f have sheared, and the plate has torn at h, leaving a piece j on the rivets k l.
“It is obvious that, since it is the same strain that has caused these different kinds of rupture, the joint has, at each location, simply given way where it was the weakest.
“If a riveted joint was to give way by tearing only, the indication would be that the proportion of strength was greatest in the rivets, which might occur from the plate being of inferior metal to the rivets, or from the rivets being too closely spaced. If the rivets were to shear and the plate remain intact, it would indicate insufficient strength in the rivets, which might occur from faulty material in the rivets, from smallness of rivet diameter, or from the rivets being too widely spaced.
“The object then, in designing a riveted joint is to have its resistance to tearing and shearing proportionately equal, whatever form of joint be employed.”
The English Board of Trade recommends that the rivet section should always be in excess of the plate section, whereas, in ordinary American practice, for stationary engine boilers, the plate and rivet percentages are made equal.
The forms of riveted joints employed in boiler work are as follows:
