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Sunday, December 10, 2023

ClassNK Updates Guidelines for Direct Load Analysis & Strength Assessment

Maritime Activity Reports, Inc.

August 29, 2022

© Nikolay / Adobe Stock

© Nikolay / Adobe Stock

Classification society ClassNK has released its Guidelines for Direct Load Analysis and Strength Assessment (Edition 2.0), which clarifies the requirements for more rational structural design reflecting the latest structural strength assessment methods based on R&D outcomes.

ClassNK’s Rules and Guidance for the Survey and Construction of Steel Ships and IACS CSR stipulate that hull strength assessment based on finite element analysis should be conducted, and the evaluation applying simplified formulae of the loads depending on ship type estimated from existing ships is required. In the case of the size lacking sufficient service record or new structurals configurationor, the method called "direct load and structural analysis”, which directly simulates the wave-induced loads acting upon ships may be used for strength assessment that accurately captures the characteristics of each ship. These guidelines (Edition 1.0) published in 2018 specify the classification requirements for these analyses.

Through the joint R&D with National Maritime Research Institute (NMRI) of Japan, it has been revealed that statistical prediction of nonlinear response quantities such as Von-Mises stress, which was previously considered impossible, is now actually possible, and requirements for strength evaluation using the statistical prediction method have been added in the guidelines. Furthermore, the update incorporates the concepts (various standards, technical background, etc.) related to structural strength assessment introduced in the comprehensively revised version of Part C of its Rules and Guidance for the Survey and Construction of Steel Ships (published as of July 1, 2022).

The class notation “PS-DA-DLA” and/or “PS-FA-DLA” is respectively affixed to the classification characters of a ship when strength assessments have been carried out for all cargo areas in accordance with the guidelines.

The guidelines are available to download via ClassNK’s website.

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