Reliability-Based Inspection of Corroded Ship-Type FPSO Hulls

2006 ◽  
Vol 50 (02) ◽  
pp. 171-180
Author(s):  
Hai-Hong Sun ◽  
C. Guedes Soares
Keyword(s):  
Ultimate Strength ◽  
Thickness Measurement ◽  
Time Dependent ◽  
Stiffened Panel ◽  
Inspection Planning ◽  
Safety Level ◽  
Buckling Strength ◽  
Hull Girder ◽  
Reliability Method ◽  
Corrosion Model

This paper proposes a time-variant probabilistic corrosion model derived from a database with 157 thickness measurement records of 140 tankers. Incorporating the corrosion model in a time-dependent reliability method and referring to a required limit of safety level, a reliability-based inspection planning is proposed for ship-type floating production, storage, and offloading units (FPSOs) based on corrosion renewal criteria that account simultaneously for thickness reduction, hull girder ultimate strength, stiffened panel buckling strength, and plate ultimate strength

Ship Hull Ultimate Strength Reliability Considering Corrosion

1998 ◽  
Vol 42 (02) ◽  
pp. 154-165
Author(s):  
Jeom Kee Paik ◽  
Anil K. Thayamballi ◽  
Sung Kyu Kim ◽  
Soo Hong Yang
Keyword(s):  
Ultimate Strength ◽  
Reliability Index ◽  
Failure Modes ◽  
Ship Hull ◽  
Time Dependent ◽  
General Corrosion ◽  
Wave Load ◽  
Hull Girder ◽  
Corrosion Rates ◽  
Reliability Method

The aim of the present paper is to develop and demonstrate a procedure for assessment of ship hull girder ultimate strength reliability taking into account the degradation of primary members due to general corrosion. The probabilistic model for ultimate hull girder strength is established on the basis of an analytical formula that considers corrosion related time dependent strength degradation in the various failure modes. Corrosion rates and their probabilistic characterization are based on available studies using gauging data. Applicable extreme hull girder loads are calculated using a simplified direct method for wave load calculation together with the IACS design guidance formula for stillwater bending moment. The variability in strength, corrosion rates and loads are accounted for in the second order reliability method (SORM) based on calculations of the time dependent reliability index. The procedure developed is illustrated by application to both tankers and bulk carriers. For a given set of renewal criteria, apart from trends of hull girder section modulus, ultimate strength and the reliability index as a function of vessel age, the probability of steel renewal due to corrosion is also predicted.

Structural Reliability Applications in Design and Maintenance Planning of Ships Subjected to Fatigue and Corrosion

2012 ◽  
Author(s):  
Marcos Corrêa Câmara ◽  
Júlio C. Ramalho Cyrino
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Time Dependent ◽  
Maintenance Planning ◽  
Inspection Planning ◽  
Utilization Factor ◽  
Hull Girder ◽  
Target Reliability Index ◽  
Hull Structure ◽  
Reliability Method

This paper presents structural reliability applications in design and maintenance planning for ships hull structures. For the assessment of structural strength, the model developed consists in an ultimate limit-state of hull-girder considering degradation by corrosion based in a statistical investigation of time-variant hull girder strength made by ABS (American Bureau of Shipping) on 2007. The time dependent reliability index obtained with the minimum elastic section modulus required by the rules of the classification society American Bureau of shipping (ABS), of two ship designs are compared against the results obtained from the target reliability index based design. The target reliability index assessment for corroded hulls is also showed. The monte-carlo simulation reliability method is used to calculate the time-dependent reliability of the primary hull structure. Two approaches of fatigue and corrosion-enhanced fatigue time dependent reliability are developed. A long term stress range applied to a detail is fitted to a weibull distribution based in a known design life. A utilization factor is introduced in order to consider the fraction of time at sea. A risk-based inspection planning is discussed for commercial and naval vessels Both S-N curve and fracture mechanics based reliability methods are used and the results are compared. An example of reliability updating after a inspection result is showed.

Assessment of Residual Ultimate Strength of VLCC According to Damage Extents and Average Compressive Strength of Stiffened Panel

2014 ◽  
Author(s):  
Ji-Myung Nam ◽  
Joonmo Choung ◽  
Se-Yung Park ◽  
Sung-Won Yoon
Keyword(s):  
Compressive Strength ◽  
Ultimate Strength ◽  
Probabilistic Approach ◽  
Stiffened Panel ◽  
Moment Capacity ◽  
Hull Girder ◽  
Damage Area ◽  
Damage Indices ◽  
Smith Method ◽  
Average Compressive Strength

This paper presents the prediction of residual ultimate strength of a very large crude oil carrier considering damage extents due to collision and grounding accidents. In order to determine extents of damage, two types of probabilistic approaches are employed: deterministic approach based on regulations based on ABS [1], DNV [2], and MARPOL [3] and probabilistic approach based on IMO probability density functions (PDFs) (IMO guidelines [4]). Hull girder ultimate strength is calculated using Smith method which is dependent on how much average compressive strength of stiffened panel is accurate. For this reason, this paper uses two different methods to predict average compressive strength of stiffened panel composing hull girder section: CSR formulas and nonlinear FEA. Calculated average compressive strength curves using CSR formulas (IACS [5, 6]) and nonlinear FEA are imported by an in-house software UMADS. Residual ultimate moment capacities are presented for various heeling angles from 0° (sagging) to 180° (hogging) by 15° increments considering possible flooding scenarios. Three regulations and IMO guidelines yield minimum of reduction ratios of hull girder moment capacity (minimum of damage indices) approximately at heeling angles 90° (angle of horizontal moment) and 180° (angle of hogging moment), respectively, because damage area is located farthest from neutral axis.

An Approximate Calculation Approach for Ultimate Strength of Ship Hull Girder

2013 ◽  
Author(s):  
Chenfeng Li ◽  
Huilong Ren ◽  
Zhongqiu Zhao ◽  
Xiaodong Zhao ◽  
Ji Zeng ◽  
...  
Keyword(s):  
Ultimate Strength ◽  
Calculation Method ◽  
Approximate Calculation ◽  
Progressive Collapse ◽  
Beam Theory ◽  
Stiffened Panel ◽  
Collapse Mechanism ◽  
Hull Girder ◽  
Post Buckling ◽  
Progressive Collapse Analysis

The assessment of the ultimate strength of a ship structure is very important not only for the initial design but also for the operation, maintenance, and repair of the structure. There exist two typical methods to assess the ultimate strength of stiffened panel and hull girder. One is the approximate calculation method and the other is the progressive collapse analysis. The approximate calculation method is based on ship beam-theory mainly, and the ultimate moment was calculated by assuming stress distribution of the whole section of the ship girders, which can not effectively consider the structural post-buckling behaviour. Based on progressive collapse mechanism and hull’s beam theory, A approximate calculation approach was proposed. By calculating the ultimate strength of stiffened panels in the distal end hull section, the deflections were obtained when the different stiffened panel reaching in the limit state, and then the stress state and bending moment of section were determined with different deflections, the hull’s ultimate moment value is determined by searching and comparing finally. The numerical examples show that the presented method was reasonable and effective compared with traditional direct calculation method and progressive collapse analysis. The method given hereof followed the progressive collapse mechanism through inversion searching in some degree, and the structural post-buckling behaviour was effectively considering.

The application of Structural Reliability Analysis on hull girder ultimate strength of bulk carriers-a trial on Safety Level Approach

2015 ◽  
Author(s):  
Daokun Zhang ◽  
Wenyong Tang
Keyword(s):  
Reliability Analysis ◽  
Ultimate Strength ◽  
Structural Reliability ◽  
Safety Level ◽  
Hull Girder ◽  
Structural Rules ◽  
Structural Reliability Analysis ◽  
Trial Analysis ◽  
Bulk Carriers ◽  
Partial Safety Factors

The International Maritime Organization is developing the Goal Based Standard, in which the Safety Level Approach(SLA) is one of the two parallel ways forward focusing on deriving explicit and reasonable safety level. During the development of Safety Level Approach, the Structural Reliability Analysis(SRA) is recognized as one of the useful tools. The application of SRA on the calibration of partial safety factors for hull girder ultimate strength is so far a typical illustration, which could be very helpful for the application of Safety Level Approach on the structural Rules in the future. China Classification Society (CCS) carries out a trial analysis with co-operation of Shanghai Jiao Tong University.

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.

Reliability-based sensitivity analysis of ships

2005 ◽  
Vol 219 (1) ◽  
pp. 11-23
Author(s):  
J Downes ◽  
Yongchang Pu
Keyword(s):  
Ultimate Strength ◽  
Progressive Collapse ◽  
Safety Margin ◽  
Random Variables ◽  
Individual Element ◽  
Hull Girder ◽  
Analysis Methodology ◽  
Reliability Method ◽  
Collapse Analysis ◽  
Progressive Collapse Analysis

Failure of a ship hull girder is a very important failure mode, which is normally catastrophic and has severe consequences. It is of great importance to predict accurately the ultimate strength of a hull girder so that an adequate but not excessive safety margin for this failure can be ensured in the ship design. This study proposes a method for reliability-based analysis of the ultimate strength of a hull girder. The reliability method is interactively integrated with progressive collapse analysis so that the uncertainties in individual random variables relating to the prediction of the ultimate strength of a hull girder can be accurately considered in reliability analysis and that sensitivity factors of these random variables can be probabilistically evaluated. The ultimate strength will be evaluated using a progressive collapse analysis methodology with the appropriate individual element stress-strain curves derived interactively. The method is applied to two example structures and the sensitivities of the reliability to the random variables are presented.

scholarly journals Analysis of Hull Girder Ultimate Strength and Residual Strength Based on IACS CSR-H

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Gui-jie Shi ◽  
Da-wei Gao ◽  
Hong Zhou
Keyword(s):  
Ultimate Strength ◽  
Residual Strength ◽  
Influence Factors ◽  
Safety Level ◽  
Hull Girder ◽  
Common Structure ◽  
Smith Method ◽  
Bulk Carriers ◽  
Calculation Results ◽  
Oil Tankers

In order to express the safety level of hull structures, IACS Common Structure Rules of Bulk Carriers and Oil Tankers (CSR-H) makes new requirements of hull girder ultimate strength. Compared with original CSR (i.e., CSR-OT and CSR-BC), partial safety factors of hull girder ultimate strength in CSR-H have been partly modified, and new requirements of residual strength have been added in the rules for hull safety after grounded/collided damage. This paper compares the rule requirements of ultimate strength in CSR-H and CSR-OT/CSR-BC and explains the technical background of rule requirements. The hull girder ultimate strength is mainly analyzed by SMITH method in rule requirements due to fast and stable calculation results. This paper also uses nonlinear finite element method (NFEM) to explain the critical influence factors for hull girder ultimate strength implied in the rule requirements. Based on 5 typical Bulk Carriers and 4 typical Oil Tankers, the influence of hull girder ultimate strength and residual strength in CSR-H has been evaluated for ship building industry. The actual ship evaluation results can be used to instruct the new CSR-H ship design.

scholarly journals Ultimate Limit State Design Technology for Aluminum Multi-Hull Ship Structures

2005 ◽  
Author(s):  
Jeom Kee Paik ◽  
Owen F. Hughes ◽  
Paul E. Hess ◽  
Celine Renaud
Keyword(s):  
Ultimate Strength ◽  
Limit State ◽  
Extensive Study ◽  
Stiffened Panel ◽  
Ultimate Limit State ◽  
Ship Structures ◽  
Strength Assessment ◽  
Hull Girder ◽  
National University ◽  
Ultimate Limit

The present paper is a summary of recent research and developments related to some core ultimate limit state (ULS) technologies for design and strength assessment of aluminum multi-hull ship structures, jointly undertaken by Pusan National University, Virginia Tech, U.S. Naval Surface Warfare Center and Alcan Marine. An extensive study on the subject has been undertaken by the authors theoretically, numerically and experimentally. Methods to analyze hull girder loads / load effects, stiffened panel ultimate strength and hull girder ultimate strength of aluminum multi-hull ship structures are developed in the present study. Application examples of the methodologies for the ULS structural design and strength assessment of a hypothetical 120m long all aluminum catamaran fast ship structure are presented. Important insights and conclusions developed from the present study are summarized. Some of the comparisons have shown that 5383 called Sealium (a patented Alcan Marine alloy) is superior to the standard aluminum alloy 5083 in terms of material properties, ULS characteristics and welding performance. It is our hope that the methods developed from the present study will be useful for ULS design and strength assessment of aluminum multi-hull ship structures.

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