This paper presents a procedure for evaluating the long term response distribution in ship structures. A specified travel route through given geographical areas during the lifetime of the ship is defined. The individual scatter diagrams, describing the relative occurrence of different sea states for the geographical areas, are weighted with respect to the relative time occupancy of the ship. A two-dimensional analytical distribution is fitted to the weighted scatter diagram over the lifetime. Frequency responcefunctions for all the sectorial forces are calculated for different ship speeds, heading angles and loading conditions, and fitted to a bi-cubic spline. The wave spectrum is defined by applying a gamma spectrum. The response spectrum is found using a linear frequency domain analysis. From the response spectrum, the peak distribution of the response in each short termperiod, conditioned on the loading condition, the ship speed and the waveheading direction is computed. The peak distribution over the lifetime isestimated by unconditioning with respect to sea states, maneuvering and loading conditions. The long term peak distribution to be applied in a fatigue analysis is expressed through a Weibull distribution, where the distribution parameters are calibrated from fractile values. The long term extreme value distribution is estimated based on the out-crossing of the envelope response process modified for the long-run fraction of qualified excursions.
Stochastic modeling of long term wave induced responses of ship structures
Stochastische Modellierung des Langzeitverhaltens wellenerregter Schiffskonstruktionen
Marine Structures ; 7 , 6 ; 537-566
1994
30 Seiten, 8 Bilder, 4 Tabellen, 26 Quellen
Aufsatz (Zeitschrift)
Englisch
Long-Term Fatigue Damage of Ship Structures Under Nonlinear Wave Loads
Online Contents | 2002
|Long-term fatigue damage of ship structures under nonlinear wave loads
Tema Archiv | 2002
|Ordinary wave-induced responses of victory cargo ship
Engineering Index Backfile | 1963
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