Design by first principles requires explicit criteria for serviceability and safety. Structuralsafety is ensured in terms of load effects and strength depending upon relevant failuremodes, also denoted limit states. For marine structures, limit state criteria should include:ultimate (ULS); fatigue (FLS) as well as accidental collapse limit state (ALS) relates toultimate failure of the overall structure, caused by some initial damage, typically byaccidental loads or deficient strength (Fig. 12).