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FEM Structural Analysis and CAD Hull Modelling for a Bulk Carrier - a Case Study

Pintilie Alexandru, Manea Mihaela-Greti, Cristea Ovidiu, Burlacu Paul, Mărăşescu Daniel, Clinci Catalin-Paul

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2025

Vol. 19 No. 2

503--514

Due to the frequent damage encountered in the hull of bulk carriers in operation, it is necessary to analyse the possibilities to increse the performances by structural and dimensional modeling of the central area of the hull of the vessel under the effect of combined general stresses (and specific local stresses. The present paper analyzes the response of the central section of the bulk carrier of 165000 tdw for three representative cases of total stress, re-evaluated by simulation with the help of finite element analysis software. Following the interpretation of the results obtained by the finite element analysis, the authors propose some solutions to increase the structural strength of the central area of the bulk carrier of 165000 tdw. The present study shows that the structure of the cylindrical area of the hull of the analyzed ship, remodeled by finite element, ensures the compromise between the operational requirements and the design requirements imposed by the norms The structural characteristics of the central section of the ship were analyzed, the practical validation being provided by the finding that the bending moments do not exceed the permissible values imposed by the class society. Work was done on three separate cases of ship loading and corrections were made for 12 sections of the hull. The use of high-strength steel has led to a weight reduction of 22%.

A multistate approach to reliability analyses of a ship hull structure

Soszyńska-Budny Joanna, Ivošević Špiro

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2024

Vol. 18 No. 4

897--904

Structural damage in the form of corrosion, fatigue, damage, cracks and fouling can significantly reduce the structural integrity of ships in navigation and decrease the navigation safety. Therefore, numerous studies aim to improve international rules and regulations, and ensure proper maintenance of ships and timely inspections. Classification societies, flag states and port states strive to conduct appropriate inspections of ships with the aim of preventive detection of defects. Through the application of International Safety Management system, companies strive to improve maintenance systems, monitor the condition of ships and conduct risk assessments to reduce potential accidents and negative consequences for people, material goods and the environment. By means of advanced Structural Health Monitoring, the observation and analysis of the physical, chemical or electrical characteristics of components or systems are conducted over time. Such examinations tend to identify the variations that lead to degradation of the current or future performance of the inspected systems and their components. The condition of hull structures is monitored by mandatory requirements which are prescribed by classification societies e.g. the number of thickness measurements of hull structure areas and elements. The measurements create extensive databases that are further used to monitor the condition of existing ships and predict their future conditions. This study relies on a database of 25 bulk carriers aged between 5 and 25 years. The measurements were performed during regular special surveys on the total of 110 fuel tanks located in double bottom area of ships, which provided 3070 measured data in total. The values of the thickness diminution of steel plates due to corrosion were obtained through the measurements of the thickness of the steel plates by means of ultrasound thickness gauging equipment, in accordance with the rules of classification societies. Based on those rules and allowable substance and extensive corrosion, the paper considers the excessive corrosion values (above 20%) that were identified as failures and required the replacement of corroded surfaces. The multistate approach to the reliability analysis of the steel plates of inner bottom plating and the improvement of reliability after critical conditions showed that the usability of the analyzed ships significantly dropped after 15 years of exploitation.