Offshore structural components such as pipelines and risers should be assessed for fatigue. Sources of cyclic loadings that should be considered are as follows:
- Loads during installation of pipeline
- Startup and shutdown of the pipeline system
- Pressure and temperature fluctuations
- Vortex Induced Vibration
- Wave induced hydrodynamic loads
- Platform movements
In cases when number of load cycles is high and stress level is relatively low (high cycle fatigue), fatigue analysis should be assessed based on available laboratory tests or results of tests presented in codes or recommended practices. One of the most popular recommended practices in this area is DNV-RP-C203, Fatigue Design of Offshore Steel Structures. In cases when number of load cycles is relative low and the stress level in the pipeline is relatively high (low cycle fatigue), the following equation from the American Welding Society (AWS) may be used. 
Where, ?? is total amplitude (range) of strain (maximum strain - minimum strain). Reference: Pipeline and Risers, Dr. Yong Bai., Elsevier Ocean Engineering Book Series.
