Several failures of metallic engineering structures occur due to cyclic loading. The failure process often consists of three stages : (a) crack initiation (from microcrack initiation to engineering-size flaw formation), (b) crack propagation, and (c) final failure. The fatigue phenomena remarkably affect joints and components in the field of the offshore structures. As a matter of fact, these structures are subjected to a severe cyclic loading, and the crack propagation rate is increased by the environmental conditions under which they usually work.