Structural Reliability of a Suezmax Oil Tanker Designed According to New Joint Tanker Project Rules

2006 ◽  
Author(s):  
C. Guedes Soares ◽  
Josˇko Parunov
Keyword(s):  
Structural Reliability ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Single Step ◽  
Moment Capacity ◽  
Hull Girder ◽  
Term Operation ◽  
Reliability Method ◽  
Wave Induced

The paper aims at quantifying the changes in notional reliability levels that result from redesigning an existing suezmax tanker to comply with new Joint Tanker Project (JTP) rule requirement for ultimate vertical bending moment capacity. The probability of structural failure is calculated using a first-order reliability method. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance to IACS recommended procedure. Comparative analysis of long-term distributions of vertical wave bending moment calculated by two independent computer seakeeping codes is performed. The still water loads are defined on the basis of a statistical analysis of loading conditions from the loading manual. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by JTP single-step procedure and by program HULLCOLL for progressive collapse analysis of ship hull-girders. The reliability assessment is performed for “as-built” and “corroded” states of the existing ship and a reinforced design configuration complying with new JTP rules. It is shown that hull-girder failure probability of suezmax tanker reinforced according to new JTP rules is reduced several times. Sensitivity analysis and a parametric study are performed to investigate the variability of results to the change of parameters of pertinent random variables within their plausible ranges.

Structural Reliability of a Suezmax Oil Tanker Designed According to New Common Structural Rules

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
C. Guedes Soares ◽  
Joško Parunov
Keyword(s):  
Structural Reliability ◽  
International Association ◽  
Bending Moment ◽  
Single Step ◽  
Hull Girder ◽  
Structural Rules ◽  
Term Operation ◽  
Reliability Method ◽  
Common Structural Rules

The paper aims at quantifying the changes in notional reliability levels that result from redesigning an existing suezmax tanker to comply with new Common Structural Rules (CSR) requirement for ultimate vertical bending moment capacity. The probability of structural failure is calculated using a first-order reliability method. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance to International Association of Classification Societies (IACS) recommended procedure. Comparative analysis of long-term distributions of vertical wave bending moment calculated by two independent computer seakeeping codes is performed. The still-water loads are defined on the basis of a statistical analysis of loading conditions from the loading manual. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by CSR single-step procedure and by program HULLCOLL for progressive collapse analysis of ship hull-girders. The reliability assessment is performed for as-built and corroded states of the existing ship and a reinforced design configuration complying with CSR. It is shown that hull-girder failure probability of suezmax tanker reinforced according to new CSR is reduced several times. Sensitivity analysis and a parametric study are performed to investigate the variability of results to the change of parameters of pertinent random variables within their plausible ranges.

Hull-Girder Reliability of a Chemical Tanker

2009 ◽  
Vol 46 (04) ◽  
pp. 192-199
Author(s):  
Jôsko Parunov ◽  
Maro Corak ◽  
C. Guedes Soares
Keyword(s):  
International Association ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Single Step ◽  
Hull Girder ◽  
Structural Rules ◽  
Term Operation ◽  
Reliability Method ◽  
Reliability Bound ◽  
Oil Tanker

The aim of the paper is to calculate hull-girder reliability of chemical tanker according to the reliability model proposed by International Maritime Organization (IMO). The probability of hull-girder failure is calculated using a first-order reliability method for two operational profiles—one typical for oil tanker and the other one modified in order to reflect differences between oil tanker and chemical tanker. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance with International Association of Classification Societies (IACS) recommended procedure. The stillwater loads are defined on the basis of a statistical analysis of loading conditions from the loading manual. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by progressive collapse analysis and by single-step procedure. The reliability analysis is performed for "as-built" ship and for "corroded" ship according to corrosion deduction thickness from new Common Structural Rules for double-hull oil tankers. It is shown that hull-girder failure probability of "as-built" chemical tanker is well above the upper reliability bound proposed by IMO, while the "corroded" ship is slightly unconservative since the reliability index is lower than IMO lower reliability bound.

Experimental Assessment of Form Based Approach for Predicting Extreme Value Distribution of Hull Girder Bending Moment in a Ship

2019 ◽  
Author(s):  
Tomoki Takami ◽  
Yusuke Komoriyama ◽  
Takahiro Ando ◽  
Kazuhiro Iijima
Keyword(s):  
Estimation Method ◽  
Bending Moment ◽  
Extreme Value Distribution ◽  
Irregular Waves ◽  
Extreme Wave ◽  
Scaled Model ◽  
Element Analysis ◽  
Hull Girder ◽  
Reliability Method ◽  
Wave Induced

Abstract This paper describes a series of towing tank tests using a scaled model of a recent container ship for validating the First Order Reliability Method (FORM) based approach to predict the maximum response. The FORM based approach is adopted in conjunction with the nonlinear strip method as an estimation method for the most probable wave episodes (MPWEs) leading to the given extreme wave-induced vertical bending moments (VBMs). Tank tests under the pre-determined MPWEs are conducted to evaluate the extreme wave-induced VBMs. Numerical simulations based on the coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) are also conducted and are compared with the test results under the MPWEs. Furthermore, to estimate the extreme VBM statistics, tank tests under random irregular waves are conducted. A series of validations of the probability of exceedances (PoEs) of the VBM evaluated from the FORM based approach is carried out. The effect of hydroelastic (whipping) vibrations on the extreme VBM statistics are finally discussed.

Hull-Girder Reliability of an Aged Oil Tanker

2008 ◽  
Author(s):  
Josˇko Parunov ◽  
Paulo Mage ◽  
C. Guedes Soares
Keyword(s):  
Transfer Functions ◽  
International Association ◽  
Single Step ◽  
Hull Girder ◽  
Structural Rules ◽  
Term Operation ◽  
Strip Theory ◽  
Reliability Method ◽  
Years Of Service ◽  
Oil Tanker

The aim of the paper is to assess the hull-girder reliability of an existing single-hull oil tanker after 25 years of service using a reliability method and assumptions very similar to those proposed recently by International Maritime Organization (IMO). The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance with the International Association of Classification Societies (IACS)-recommended procedure, while transfer functions are calculated using the linear strip theory. The still-water loads are defined on the basis of statistical analysis of data recorded on single-hull oil tankers. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by progressive collapse analysis and by a single-step procedure according to Common Structural Rules (CSR). The reliability analysis is performed for three states of the hull: as built ship with scantlings of the new ship, CSR corroded state with net thicknesses of the structural members according to the corrosion deduction thickness proposed by CSR and survey state with scantlings according to the thickness measurements after 25 years of service. The yearly probability of structural failure is calculated using the first-order reliability method, while sensitivity analysis and a parametric study are performed to investigate the variability of the results with changes of the random variables within their plausible ranges. Results of the analysis are compared with recommended target reliability indices proposed by IMO and also with the results of the reliability assessment of the new double-hull tanker. Such comparison is possible since similar reliability methods and uncertainty models are employed. Results of the analysis may have several useful applications related to the decision-making aspects of the future of an aged oil tanker.

Time-Variant Redundancy of Ship Structures

2011 ◽  
Vol 55 (03) ◽  
pp. 208-219 ◽  
Author(s):  
Alberto Decó ◽  
Dan M. Fragopol ◽  
Nader M. Okasha
Keyword(s):  
Bending Strength ◽  
Progressive Collapse ◽  
Probability Of Failure ◽  
Optimization Approach ◽  
Ship Structures ◽  
Hull Girder ◽  
Reliability Method ◽  
Ultimate Bending Strength ◽  
Ultimate Failure ◽  
Bending Failure

An efficient procedure for the computation of the redundancy of ship structures is presented. The changes in the redundancy due to corrosion section loss over time are also studied. Moreover, uncertainties associated with structural geometry, material properties, and loading, are accounted for. In order to calculate the redundancy index, the probability of failure of the first component and the probability of ultimate failure of the whole hull girder must be evaluated. The probability of failure is computed using a hybrid Latin Hypercube - second-order reliability method (SORM) technique. The deterministic analyses during the simulations are conducted using an optimization approach for computing the ultimate bending strength of the whole hull girder and the progressive collapse method for computing the first bending failure.

Load Combination for Fatigue Analysis of Ship Structures

2004 ◽  
Author(s):  
Yung S. Shin ◽  
Booki Kim ◽  
Alexander J. Fyfe
Keyword(s):  
Bending Moment ◽  
Linear Summation ◽  
Load Combination ◽  
Longitudinal Stiffeners ◽  
Stress Components ◽  
Tank Pressure ◽  
Wave Induced ◽  
Vertical Bending Moment ◽  
Oil Tanker

A methodology for calculating the correlation factors to combine the long-term dynamic stress components of ship structure from various loads in seas is presented. The methodology is based on a theory of a stationary ergodic narrow-banded Gaussian process. The total combined stress in short-tem sea states is expressed by linear summation of the component stresses with the corresponding combination factors. This expression is proven to be mathematically exact when applied to a single random sea. The long-term total stress is similarly expressed by linear summation of component stresses with appropriate combination factors. The stress components considered here are due to wave-induced vertical bending moment, wave-induced horizontal bending moment, external wave pressure and internal tank pressure. For application, the stress combination factors are calculated for longitudinal stiffeners in cargo and ballast tanks of a crude oil tanker at midship section. It is found that the combination factors strongly depend on wave heading and period in the short-term sea states. It is also found that the combination factors are not sensitive to the selected probability of exceedance level of the stress in the long-term sense.

On the Effect of Hull Girder Flexibility on the Vertical Wave Bending Moment for Ultra Large Container Vessels

2012 ◽  
Author(s):  
Ingrid Marie Vincent Andersen ◽  
Jørgen Juncher Jensen
Keyword(s):  
Bending Moment ◽  
Main Concern ◽  
Hull Girder ◽  
Numerical Predictions ◽  
Strip Theory ◽  
Reliability Method ◽  
Non Linear ◽  
Large Container ◽  
The Waves ◽  
Good Agreement

Currently, a number of very large container ships are being built and more are on order, and some concerns have been expressed about the importance of the reduced hull girder stiffness to the wave-induced loads. The main concern is related to the fatigue life, but also a possible increase in the global hull girder loads as consequence of the increased hull flexibility must be considered. This is especially so as the rules of the classification societies do not explicitly account for the effect of hull flexibility on the global loads. In the present paper an analysis has been carried out for the 9,400 TEU container ship used as case-ship in the EU project TULCS (Tools for Ultra Large Container Ships). A non-linear time-domain strip theory is used for the hydrodynamic analysis of the vertical bending moment amidships in sagging and hogging conditions for a flexible and a rigid modelling of the ship. The theory takes into account non-linear radiation forces (memory effects) through the use of a set of higher order differential equations. The non-linear hydrostatic restoring forces and non-linear Froude-Krylov forces are determined accurately at the instantaneous position of the ship in the waves. Slamming forces are determined by a standard momentum formulation. The hull flexibility is modelled as a non-prismatic Timoshenko beam. Generally, good agreement with experimental results and more accurate numerical predictions has previously been obtained in a number of studies. The statistical analysis is done using the First Order Reliability Method (FORM) supplemented with Monte Carlo simulations. Furthermore, strip-theory calculations are compared to model tests in regular waves of different wave lengths using a segmented, flexible model of the case-ship and good agreement is obtained for the longest of the waves. For the shorter waves the agreement is less good. The discrepancy in the amplitudes of the bending moment can most probably be explained by an underestimation on the effect of momentum slamming in the strip-theory applied.

Analysis of Ship Structural Loading in a Seaway

1972 ◽  
Vol 9 (02) ◽  
pp. 173-194
Author(s):  
Dan Hoffman
Keyword(s):  
Pressure Distribution ◽  
Phase Relationship ◽  
Bending Moment ◽  
Green Water ◽  
Detailed Structural Analysis ◽  
Transverse Pressure ◽  
Structural Loading ◽  
Wave Induced

The recent advent of the large tanker and bulk carrier has promoted the requirements for more detailed structural analysis of a ship and the reevaluation of theories for calculating the static, quasistatic and dynamic loads. The paper begins with discussion of the methods available to determine the various types of loads expected, their phase relationship, and ways of superimposing them. It then proceeds to the treatment of sea loads based on theoretical and experimental data, and techniques of determining the ship response in a seaway are discussed. The response to regular waves is reviewed with special reference to the determination of pressure distribution on the hull. Statistical ship response, immediate and cumulative over the life of the ship, is demonstrated in relation to the prediction of long-term bending moment trends, and the distribution of the extremes is discussed. Special loading conditions are described with special emphasis on the transverse pressure distribution, dynamic effects due to motion of liquid cargo in tanks, shipping of green water, wave-induced vibrations, slamming pressures and whipping stresses due to various causes. The paper treats the above subjects in a broad manner and no attempt to illustrate the theory in detail is made.

The Effect of Sloshing in Tanks on Motions and Hull Girder Responses of Damaged Vessels

2011 ◽  
Author(s):  
Huirong Jia ◽  
Torgeir Moan
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Bending Moment ◽  
Roll Motion ◽  
Multimodal Approach ◽  
Rectangular Shape ◽  
Hull Girder ◽  
Structural Reliability Analysis ◽  
Oil Tankers

The structural reliability analysis of damaged vessels has up to now commonly been investigated by neglecting the effect of sloshing. This paper deals with the effect of sloshing in tanks on motions and hull girder responses of oil tankers in various damage conditions and represents a part of a study to assess the effect of sloshing on hull girder failure of damaged vessels, The flooded tanks are assumed to have a of rectangular shape and linear multimodal approach is adopted to deal with sloshing. It is concluded that even though the effect of sloshing in tanks on the roll motion of vessels can be neglected in certain damage conditions, the effect of sloshing on the horizontal bending moment cannot be neglected, especially when resonance motion occurs.

Effects of Avoidance of Heavy Weather on the Wave Induced Load on Ships

2006 ◽  
Author(s):  
Zhi Shu ◽  
Torgeir Moan
Keyword(s):  
Green Water ◽  
Vertical Acceleration ◽  
Sea State ◽  
Hull Girder ◽  
Term Prediction ◽  
Strip Theory ◽  
Operational Criteria ◽  
Wave Induced ◽  
Long Term Prediction

This paper is concerned with evaluating the effect of avoidance of heavy weather on the long term wave induced loads on ships. Two hydrodynamic codes VERES based on a 2D strip theory and WASIM based on a 3D Rankine panel method are employed to calculate the wave induced loads and motions on various vessels. Two models for heavy weather avoidance are proposed. The first is based upon the assumption that operational criteria relevant to vertical acceleration, green water and bottom slamming are fulfilled. The second one is based upon the assumption that the sea state forecasts are available to the ship master, and that rerouting is made. And based on the first model considering avoidance of heavy weather and the hydrodynamics results calculated from two codes, the wave induced hull girder loads are obtained. The results are discussed. In particular, the effect of different hydrodynamic codes and various scatter diagrams are assessed. After all, the long term prediction of wave induced hull girder loads considering the effect of avoidance of heavy weather will give a relatively more realistic evaluation of the extreme hull girder loads. Finally the results from ship rules will also be re-evaluated compared with the long term prediction with and without heavy weather avoidance.

Sign in / Sign up

Export Citation Format

Share Document