Riveted Joints

um. Tensile and Compressive Strength of Riveted Plates.

The holes punched or drilled in a plate or bar weaken its tensile strength, and to compute that strength it is necessary to allow for the holes. By net section, in this connection, is meant the small est cross-section of the plate or bar ; this is always a section along a line of rivet holes.

If, as in the foregoing article, t denotes the thickness of the plates joined ; d, the diameter of the holes; ri,„ the number of riv ets in a row ; and w, the width of the plate or bar; then the net section = (w — tt,d) t.

Let denote the tensile working strength of the plate ; then the strength of the unriveted plate is wtS„ and the reduced tensile strength is (w — n,,d) t The compressive strength of a plate is also lessened by the presence of holes ; but when they are again filled up, as in a joint, the metal is replaced, as it were, and the compressive strength of the plate is restored. No allowance is therefore made for holes in figuring the compressive strength of a plate.

los. Computation of the Strength of a Joint.

The strength of a joint is determined by either (1) the shearing value of the rivets ; (2) the bearing value of the plate ; or (3) the tensile strength of the riveted plate if the joint is in tension. Let P, de note the strength of the joint as computed from the shearing values of the rivets ; P., that computed from the bearing value of the plates ; and P„ the tensile strength of the riveted plates. Then, as before explained, n, denoting the total number, of rivets in the joint ; and n, denot ing the total number of rivets in a lap joint, and one-half the number of rivets in a butt joint.

.Examples. 1. Two half-inch plates 71 inches wide are eon netted by a single lap joint double-riveted, six rivets in two rows. If the diameter of the rivets is / inch, and the working strengths are as follows : 12,000, 7,500, and 15,000 pounds per square inch, what is the safe tension which the joint can transmit ? Here n,== 3, n= 6, and 6 ; hence 1 3 1