Members are connected by rivet which can not be removed unless the rivet is destroyed. Rivets are either fitted at site or in the fabrication shop. The former is called field rivets and the latter as shop rivets.
Rivets used in building construction are of soft steel with a tensile strength of the order of about 4000 kg/cm2. Sometimes wrought iron rivets are favoured as it has the property of retaining malleability even longer than that of steel after being forged.
Generally rivets have a hemispherical button-shaped head and a cylindrical shank. Other shapes are flattered head and counter sunk head. Semi-circular button head is used commonly. Wherever more clearance is needed flattered head is used. Counter-sunk heads are used when least projections are needed.
The process of driving a rivet is first to heat the rivet red hot and to place in a hole through the members which are to be connected. The projecting end is then upset to form the head of required shape with the aid of a pneumatic hydraulic riveter. While driving, the other end of the rivet is held in place by a dolly. The rivet contracts as it cools, and thereby tightening the grip. At times cutting of rivets may become necessary. In such cases, this is accomplished by chipping off the head with a pneumatic chipper and then the rivet is driven out with a pin-maul.
Centre-to-centre distance between the adjacent rivets on the same rivet line is called pitch. Minimum pitch is generally three times the diameter of the finished rivet. However, the absolute minimum pitch is twice the diameter of the rivet plus one cm.
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