Numéro : 2517 - Year : 2008
Some aspects of hydro structural issues in the design of ultra large container ships
Michel HUTHER, BUREAU VERITAS – Division Marine – Paris (France)
Sime MALENICA, BUREAU VERITAS – Division Marine – Paris (France)
Florence MAUDUIT, BUREAU VERITAS – Division Marine – Paris (France)
Recent trends in increasing the size of the container ships (up to 400m in length), raise the new hydro structural issues in their design and verification process, both from ultimate strength and fatigue points of view. Some of these issues are related to the hydroelastic structural responses which become important due to the relatively low structural natural frequencies of these ships, and due to the strong operational requirements (maximum speed around 27 knots). Indeed, the combination of the reduced natural frequencies and increased excitation frequency can lead to the forced wave induced hull girder ship vibrations called springing, which might significantly affect the ship fatigue life. In addition to this, the slamming induced transient vibration (whipping) can affect both the ultimate strength and fatigue. In any case, the classical classification society’s rules are reaching their limits for these ships and the so called direct calculation approach is needed. In this paper the over-all Bureau Veritas procedure based on direct calculations is presented and discussed.