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

• Main Authors: JURIŠIĆ, Paul, PARUNOV, Joško, SENJANOVIĆ, Ivo
• Format: Text
• Language: English
• Published: Brodarski Institute d.o.o. 2007
• Subjects: Aframax tankers; bending moment; fatigue strength; hull girders; vertical waves; North Atlantic
• Online Access: http://hrcak.srce.hr/16588; http://hrcak.srce.hr/file/25138

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 have recently been introduced into CSR because of frequent crack appearances on the 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 an Aframax oil tanker fully complying with “old” rules of classification societies. Since the results of fatigue calculation for initial structure have not been found acceptable, a significantly increased hull section modulus is necessary as the only practical way for the deck longitudinal fatigue life improvement. In practice, the vertical wave bending moment at midship, as the primary cause of hull girder fatigue damage, is calculated according to a simplified CSR formula. In order to improve the knowledge of its influence on the calculated fatigue life, the wave bending moment is also determined directly by a hydrodynamic and statistical analysis. In that analysis, the North Atlantic navigation is assumed as design wave environment for three predominant loading conditions. It is obvious that such an approach enables a more detailed and rational fatigue analysis than the one carried out according to the CSR rules.