Hull girder ultimate strength methods in ship structural design and analysis

A brief overview of various aspects and current issues regarding the existing methodology for the hull girder ultimate strength assessment is given. Comparison of the results obtained by a different existing ultimate bending capacity assessment methods for a different hull girder structures is presented, with particular emphasis on the results obtained by a subgroup comprised of the various incremental-iterative progressive collapse analysis (PCA) methods based on the Smith’s approach. Furthermore, results of the hull girder ultimate strength analyses of an oil tanker structures (Aframax, Suezmax and VLCC) damaged by the collision and/or grounding are presented. The PCA method prescribed by the incoming IACS H-CSR Harmonized Common Structural Rules is used for determination of the ultimate (vertical) bending moments of the considered structures. The size and position of a ship’s side and/or bottom damage is defined in accordance with the IACS H-CSR. Proposed analytical formulations of the relationship between reduction of the hull girder ultimate bending moment (with respect to the undamaged state) and damage size and position are based on a systematic variation of the ship’s side and/or bottom damage size and position.