Equivalent design wave

An equivalent design wave (EDW) is a single regular wave, defined by amplitude, period (or length), heading, and phase, chosen so that a selected structural response equals its long-term extreme value from full spectral analysis. The procedure picks a dominant load parameter, runs a long-term response prediction to get the target response at the design probability (often 10-to-the-minus-8), then back-calculates the regular-wave amplitude that reproduces that response at the response-peak frequency. The IACS Common Structural Rules apply EDWs such as case H (head-sea vertical bending), F (following sea), R (roll), and P (waterline pressure). It replaces costly direct spectral load cases with a few deterministic waves for finite element strength assessment.