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Vibrating loads lead to stress concentrations in welded joints of steel structures with complex geometries. Generally, the quality of welded joints is crucial for the life cycles of marine structures, because incorrect welding in their bearing systems leads to fatigue cracks and damage. Hence, sufficient quality for the welded joints in these structures which are exposed to high complex loads , is required (Refs .1-8). Figure 2 represents the welded joint shapes of thick sheet metals with and without joint preparation that are most frequently used in both shipbuilding and other steel structures. The weld joints can easily be made with conventional methods such as gas metal arc welding (GMAW).In shipbuilding, the GTAW process is used for welding highly alloyed steel and aluminum, especially in catamaran and yacht building. However, thick sheet metal welding joint preparation can only be manufactured with high-intensity arc welding methods such as electron beam and laser beam welding, as exhibited in Fig .2 in Fields III/1-3.
Generally, plate thicknesses, welding methods to be applied , and dynamic loads affecting marine structures determine the selection of the weld shapes. In addition, the choice of the weld shape strongly affects the welding process and the manufacturing costs. Minimization of joint volumes, renouncement of joint preparation , and omission of pre-and post treatment of welded joints reduce manufacturing costs of marine vessels and structures. These topics have been the subject of investigations around the world . Efficient welding power sources, new welding methods, and new welding techniques are also being tested . Furthermore, fatigue strength of welded joints subjected to operating loads has been intensively examined (Refs.1-12).