In proportioning riveted joints, the friction between the plates caused by the clamping effect of the rivets is neglected. Hence, a riveted joint may fail in two ways, namely, by the shearing of the rivets, and by the crippling or crushing of the metal in the member around the rivet hole. It is necessary therefore, in designing a riveted joint, to consider, besides the shearing of the rivets, the bearing value of the plates or rolled sections.

The strength of a riveted joint also depends upon the distribution of the members connected, and the location of the rivets; that is, whether the rivets are in single or double shear, and the members connected in ordinary or web bearing.

A rivet may be in single shear, as at (a), or in double shear as shown at (6), in Fig. 29. At (a) the tendency is to shear the rivet along the line ab, and the strength of the rivet is equal to its sectional area multiplied by the shearing strength of the material composing it. At (6) the tendency is to shear the rivet along the lines a b and c d; hence, the strength of the rivet in this case is twice that of the former, and is equal to twice the sectional area of the rivet, multiplied by the shearing strength of the material in the rivet.

The plates or structural sections composing a joint tend to fail or cripple, as at a, Fig. 30. Hence, the bearing strength of a plate is equal to the thickness of the plate multiplied by the diameter of the rivet and this product by the bearing strength of the material composing the plates or rolled sections. Where the plate is situated, as at (6), Fig. 29, between two outside plates, the central plate is said to be subjected to web bearing, and it is usual to consider the value of this plate, in resisting bearing, to be a third higher than in ordinary bearing, as at (a).

The most reliable test of steel and iron is the tensile, and the shearing and, bearing values are deduced from it. Conservative practice takes shearing values for high-grade iron and steel at 3/4 of the tensile strength of the material, and the ordinary bearing value at 1 1/2 times the tensile, while web bearing is taken at twice the tensile strength. On this basis the following table is formed:

Strength Of Rivets And Pins Rivets 266

Fig. 29.

Strength Of Rivets And Pins Rivets 267

Fig. 30.