engleski

Assessment of Aframax Tanker Hull-Girder Fatigue Strength According to New Common Structural Rules

The paper describes the fatigue strength assessment of ship hull girder according to Common Structural Rules for oil tankers (CSR). Additional criteria for hull girder fatigue calculation are recently introduced in CSR because of frequently crack appearances in main deck structure of large tankers. Hull girder fatigue check in CSR is performed in two steps: preliminary “ fatigue section modulus” verification and detail fatigue calculation of deck longitudinals. The analysis is performed for Aframax oil tanker fully complying with “ old” rules of classification societies. Since the results of fatigue calculation for initial structure are not at acceptable level, significant increase of hull section modulus is necessary as only practical way for deck longitudinal fatigue life improvement. Vertical wave bending moment at midship, as primary cause of hull girder fatigue damage is calculated in practice according to simplified CSR formula. In order to improve knowledge of influence of wave bending moments on calculated fatigue life, these are determined also directly by hydrodynamic and statistical analysis. In that analysis, the North Atlantic navigation is assumed during all time operations for three predominant loading conditions. Such approach enables more detailed and rational fatigue analysis comparing to CSR rules.

aframax tanker; bending moment; fatigue strength

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