Fatigue Design Factor/ Design Fatigue Factor (FDF/DFF)

Design fatigue factors (DFFs) are related to partial safety factors used in code-based design of any structure or its component to take care of uncertainties associated with the design process. DFFs are related to the fatigue failure probability and ultimately proportional to reliability against fatigue failure. Higher DFFs imply higher reliability. The DFF is generally determined by calibration and by experiences. DFF may vary for different kind of structure based on consequences of failure and on the type of detail and it may vary within a structure lacking accessibility to inspections.