Study On Fatgue Analysis Of Oil Tanker Hull

Fatigue is responsible for a large portion of cracks occurring in welded oil tanker structural details. For many years, fatigue related failure has become a major concern in the maintenance of existing vessels. A lot of oil tanker failure was reported in recent years, which attracted much attention of navigation industry. After investigation and analysis, fatigue crack was suspected to be one of main causes. The fatigue cracks were discovered mostly on the side longitudinals at the connections to transverse bulkheads or transverse webs. Considerable effort in the development of fatigue requirements and computer programs has been devoted to cope with assessment of fatigue of structures.The demand of disposal or scraping of old oil tankers has been highlighted since the accident of Erika. It is necessary to develop a procedure for existing oil tankers to determine the technical situation, especially fatigue situation of tanker hulls.In the paper, a fatigue assessment and evaluation procedure is developed based on the introduction of general fatigue analysis procedure of ship hulls and in detail discussion of simplified fatigue analysis of oil tanker hulls. Fatigue evaluation methods are introduced to establish a fatigue assessment model for tanker hulls. To provide a practical tool for fatigue assessment, this approach is based on the so-called Simplified Fatigue Analysis with the assumption that the long-term stress histogram of the hull structure follows the Weibullprobability distribution, the S-N curves used in the assessment and evabatbn are the Basic Design -N Curves for non-nodal Johts' issued by DEn(Department of Energy of United Kingdom), combining with computer technology the assessment procedure is programmed, which will indicate the fatigue damage condition and degree of technical status of tanker hulls. Tanker operators can take advantage of the results of the procedure to determine whether the tanker is to be disposed or repaired or just let it be.The oil tanker hull fatigue assessment and evaluation procedures, implementations and illustrations are presented.