5. Weld Quality Levels for Fatigue Loaded Structures

The imperfections and their classification into quality groups are mostly done by the guidance of introduced codes. One standard for weld quality is ISO 5817. This standard is an adoption of the old German standard DIN 8563, which was established as a standard for communication between the welders and the inspectors. The classification criterion was the difficulties, the expenses, or the efforts to fabricate or to inspect by NDT. So by the nature, ISO 5817 has limits in direct application to fatigue problems, it is inconsistent with respect to fatigue properties and needs application guidance. Most dedicated design codes specify a general quality level according to ISO 5817 and give additional regulations. In this situation, the IIW fatigue design recommendations have extended the scope of usual fatigue design codes by describing the fatigue properties of joints containing weld imperfections on a scientific basis.