Standard wave (IACS Rec. 34)

IACS Recommendation No. 34 defines the standard wave data used as the design environment for ship structural rules, fatigue, and seakeeping in the classification societies. Its core is the North Atlantic wave scatter diagram, a joint table of significant wave height H_s against zero-up-crossing or peak period covering the most severe global ocean climate, paired with a spectral form (historically a two-parameter Pierson-Moskowitz / Bretschneider spectrum, with JONSWAP and directional spreading in the updated revision). It underpins the Common Structural Rules design loads and the 25-year, 10-to-the-minus-8 probability extreme loads. Revision 2 (2023) updated the diagram from modern satellite, hindcast, and buoy data.