Collapse Analysis of Ship Hull Girder in Waves Using Idealized Structural Unit Method

2016 ◽  
Author(s):  
Masahiko Fujikubo ◽  
Kazuhiro Iijima ◽  
Zhiyong Pei ◽  
Han Htoo Htoo Ko
Keyword(s):  
Simple Procedure ◽  
Progressive Collapse ◽  
Ship Hull ◽  
Element Formulation ◽  
Total System ◽  
Plate Element ◽  
Hull Girder ◽  
Hull Structure ◽  
Collapse Analysis ◽  
Progressive Collapse Analysis

Recent progress in the development and application of the ISUM plate element is highlighted with a particular focus on its application to the progressive collapse analysis of a ship hull structure. The plate element is characterized by idealized shape functions for defection based on buckling collapse mode and a simple procedure for element formulation similar to that for standard displacement-based finite elements. The formulation of the plate element under in-plane loads is presented, and then the plate element and the plate-stiffener combination model are applied to the progressive collapse analysis of a hull-girder cross section and double bottom structure. The development of a total system for motion/collapse analysis of a whole ship in waves is also presented. The effectiveness of these ISUM models is demonstrated.

Evaluation of Ultimate Hull Girder Strength in Longitudinal Bending: Historical Review and Smith’s Method

2016 ◽  
Author(s):  
Tetsuya Yao
Keyword(s):  
Progressive Collapse ◽  
Historical Review ◽  
General Situation ◽  
Average Strain ◽  
Simple Method ◽  
Hull Girder ◽  
Research Activities ◽  
Collapse Analysis ◽  
Longitudinal Bending ◽  
Progressive Collapse Analysis

Ultimate hull girder strength in longitudinal bending is the most important strength of ship structure. In the present paper, firstly, historical review is made regarding the research activities regarding the ultimate hull girder strength evaluation. Then, focusing on the Smith’s method, possibility of simplified method is discussed including what are the limitations of a simple method and how it can be extended to more general situation. A simple method is introduced to derive average stress-average strain relationships of stiffener elements with attached plating. At the end, results of some example calculation are introduced to demonstrate the effectiveness of a simple method for progressive collapse analysis of a ship hull girder.

Collapse Analysis of Ship Hull Girder Using Hydro-Elastoplastic Beam Model

2018 ◽  
Author(s):  
Han Htoo Htoo Ko ◽  
Akira Tatsumi ◽  
Kazuhiro Iijima ◽  
Masahiko Fujikubo
Keyword(s):  
Cross Sections ◽  
Progressive Collapse ◽  
Ship Hull ◽  
Average Stress ◽  
Beam Model ◽  
Structural Elements ◽  
Hull Girder ◽  
Collapse Analysis ◽  
Strain Relationship ◽  
Collapse Behavior

A method of time-domain collapse analysis of ship hull girder considering the interaction between elastoplastic deformation and hydrostatic/dynamic forces is developed. Ship hull girder is longitudinally divided by conventional beam elements, and progressive collapse behavior of cross sections is simulated by Smith method considering material yielding, buckling and post-buckling of structural elements. Average stress–average strain relationship of structural elements is transformed to average stress–average plastic strain relationship so that it can be treated as pseudo strain-hardening/softening effects. Strip method is used for the calculation of hydrodynamic forces on the hull girder. Hydrodynamic coefficients for cross-sections are calculated by 2D-BEM. In-house analysis code is developed and applied to the collapse analysis of a uniform hull-girder model under impulsive bending loads. The effects of load duration time on the dynamic collapse behavior of the hull girder are discussed.

A Guide for the Ultimate Longitudinal Strength Assessment of Ships

2004 ◽  
Vol 41 (03) ◽  
pp. 122-139
Author(s):  
Jeom Kee Paik
Keyword(s):  
Progressive Collapse ◽  
Limit State ◽  
Bending Moment ◽  
Ship Hull ◽  
Safety Measure ◽  
Ultimate Limit State ◽  
Ship Hulls ◽  
Collapse Analysis ◽  
Longitudinal Strength ◽  
Progressive Collapse Analysis

The aim of the present paper is to establish a practical guide for the ultimate longitudinal strength assessment of ships. The ultimate hull girder strength of a ship hull can be calculated using either the progressive collapse analysis method or closed-form design formulas. In the present paper, both the progressive collapse analysis method and the design formulas are presented. A comparison between the progressive collapse analysis results and the design formula solutions for merchant cargo ship hulls is undertaken. The total design (extreme) bending moment of a ship hull is estimated as the sum of the still-water and wave-induced bending moment components as usual. The safety measure of a ship hull is then defined as a ratio of the ultimate longitudinal strength to the total design bending moment. The developed guidelines are applied to safety measure calculations of merchant ship hulls with respect to hull girder collapse. It is concluded that the guidance and insights developed from the present study will be very useful for the ultimate limit state design of newly built ships as well as the safety measure calculations of existing ship hulls. The essence of the proposed guide shall form ISO code 18072-2: Ships and Marine Technology— Ship Structures—Part 2: Requirements of Their Ultimate Limit State Assessment.

scholarly journals Progressive Collapse Analysis of Intact and Damaged Ships under Unsymmetrical Bending

2020 ◽  
Vol 8 (12) ◽  
pp. 988
Author(s):  
Burak Can Cerik ◽  
Joonmo Choung
Keyword(s):  
Structural Damage ◽  
Progressive Collapse ◽  
Arbitrary Cross Section ◽  
Neutral Axis ◽  
Hull Girder ◽  
Adverse Conditions ◽  
Collapse Analysis ◽  
Unsymmetrical Loading ◽  
Double Hull ◽  
Progressive Collapse Analysis

This study examined the hull girder strength of intact and damaged ships by adopting the incremental-iterative method for progressive collapse analysis, which was extended to the general case of the unsymmetrical bending of beams with an arbitrary cross-section. The sources of an unsymmetrical loading, including rotation of the loading plane and section asymmetry caused by structural damage, are described. A fast and robust procedure is presented to determine the translation and rotation of the instantaneous neutral axis at each curvature increment when applying Smith’s progressive collapse analysis method. A series of analyses were conducted on a double hull VLCC and a bulk carrier, considering various loading plane angles and damage conditions. The decrease in ultimate strength and the influences of rotation of the instantaneous neutral axis and ship heeling are discussed. The proposed method can be used for a rapid and rational assessment of the hull girder strength under adverse conditions.

scholarly journals Progressive Collapse Analysis of an FPSO Vessel Hull Girder Under Vertical Bending Considering Different Corrosion Models

2020 ◽  
Author(s):  
Zorareh Nouri ◽  
Mohammad Reza Khedmati
Keyword(s):  
Ultimate Strength ◽  
Pitting Corrosion ◽  
Progressive Collapse ◽  
Relative Reduction ◽  
Uniform Corrosion ◽  
Hull Girder ◽  
Operational Life ◽  
Collapse Analysis ◽  
Corrosion Model ◽  
Progressive Collapse Analysis

Abstract Nowadays, with the increasing operational life of ships, the aging effects on their structural behavior need to be investigated precisely. With the corrosive marine environment taken into consideration, one of the important effects of aging that must be studied is thickness degradation. In this paper, with the use of previously proposed equivalent thickness formulations for corroded plates, the progressive collapse analysis software HULLST is enhanced, and then, the effects of different corrosion models of uniform, random, pitting, and tanker pattern types on the ultimate and residual strengths of a floating production, storage, and offloading vessel hull girder are evaluated for the ages of 0 to 25 years. Results reveal that the uniform corrosion and random corrosion models have close outcomes. The value of relative reduction in the ultimate strength of ship hull girder (compared with the intact condition) ranges roughly from 6% for the age of 5 years to 17% for the age of 25 years in the hogging mode. The relative reduction in the ultimate strength ranges from 4% to 16% in the sagging mode. Pitting corrosion and tanker pattern (random) corrosion models lead to higher relative reductions in ultimate strength. The pitting corrosion model leads to a 16%–32% relative reduction in the ultimate strength for the ages of 5–25 years of the ship in either hogging or sagging. The tanker pattern (random) corrosion model leads to a 6%–37% relative reduction in the ultimate strength in the hogging mode and 3%–31% in the sagging mode at ship ages of 5 to 25 years.

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