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.

Estimation of hull girder vertical bending moments including non-linear and flexibility effects using closed form expressions

2009 ◽  
Vol 223 (3) ◽  
pp. 377-390 ◽  
Author(s):  
P T Pedersen ◽  
J J Jensen
Keyword(s):  
Closed Form ◽  
Linear Response ◽  
Bending Moment ◽  
Phase Lag ◽  
Bending Moments ◽  
Hull Girder ◽  
Strip Theory ◽  
Non Linear ◽  
Bow Flare ◽  
Wave Induced

A simple but rational procedure for prediction of extreme wave-induced hull girder bending moment in slender mono-hull displacement vessels is presented. The procedure takes into account main ship hull characteristics such as length, breadth, draught, block coefficient, bow flare coefficient, forward speed, and hull flexibility. The wave-induced loads are evaluated for specific operational profiles. Non-linearity in the wave bending moment is modelled using results derived from a second-order strip theory and water entry solutions for wedge-type sections. Hence, bow flare slamming is accounted for through a momentum type of approach. The stochastic properties of this non-linear response are calculated through a monotonic Hermite transformation. In addition, the impulse loading attributable to, for example, bottom slamming or a rapid change in bow flare is included using a modal expansion in the two lowest vertical vibration modes. These whipping vibrations are added to the wave frequency non-linear response, taking into account the rise time of the impulse response as well as the phase lag between the occurrence of the maximum non-linear load and the maximum impulse load. Previous results for the sagging bending moment are validated by comparison with fully non-linear strip theory calculations and supplemented with new closed form results for the hogging bending moment. Focus is on the extreme hull girder hogging bending moment. Owing to the few input parameters, this procedure can be used to estimate the wave-induced bending moments at the conceptual design phase. Another application area is for novel single-hull ship types not presently covered by the rules of the classification societies. As one application example the container ship MSC Napoli is considered. Further validations are needed, however, in order to select proper values of the parameters entering the analytical form of the slamming impulse.

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.

Large deflection of elastoplastic, non-linear strain-hardening cantilevers

2001 ◽  
Vol 216 (4) ◽  
pp. 433-446 ◽  
Author(s):  
X Huang ◽  
B Wang ◽  
G Lu ◽  
T X Yu
Keyword(s):  
Strain Hardening ◽  
Large Deflection ◽  
Rectangular Cross Section ◽  
Bending Moment ◽  
Linear Strain ◽  
Non Linear ◽  
Theoretical Predictions ◽  
Strain Relationship ◽  
Inclined Angle ◽  
Good Agreement

This paper concerns the large deflection of elastoplastic, non-linear strain-hardening cantilevers of rectangular cross-section, for which the stress-strain relationship after yielding is described by σ= K1εq. Both the bending moment and axial force are included in the yielding criterion, and the corresponding strain increments obey the associated normality rule. Comparisons between the experimental data and the theoretical predictions are made for mild steel cantilevers subjected to a tip force with an inclined angle ϕ = 67.5,90 and 157° respectively. Reasonable agreement is obtained. The theoretical analysis has described the large deflection behaviour of the cantilever and is in good agreement with tests.

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.

Numerical Study for the Progressive Collapse of Scale Model for ULCS Hull Girder Under Longitudinal Bending

2018 ◽  
Author(s):  
Chonglei Wang ◽  
Deyu Wang
Keyword(s):  
Numerical Study ◽  
Progressive Collapse ◽  
Similarity Criterion ◽  
Bending Moment ◽  
Scale Model ◽  
Stiffened Panels ◽  
Hull Girder ◽  
Load Carrying ◽  
Longitudinal Bending ◽  
Large Container

For evaluating reliable load carrying capacity of actual hull girder, experiments for similar scale model are necessary. The object of the present paper is to figure out a reliable FE analysis method in the similar scale model experiment regarding hull girder ultimate strength. The compared results between the true hull girder of a typical ultra large container ship (ULCS) and the scale experimental model created by the similarity criterion proposed in this paper assessed by finite element method (FEM) under longitudinal bending moment considering the effects of initial deflections are obtained guaranteeing the similarity in both elastic and inelastic range during the progressive collapse of plates, stiffened panels and hull girder. Finally, a series of elastic-plastic large deflection analyses is conducted to ensure the failure mode of hull girder is consistent with the actual ship.

Examination of Effect of Lateral Loads on the Hull Girder Ultimate Strength of Large Container Ships

2016 ◽  
Author(s):  
Toshiyuki Matsumoto ◽  
Toshiyuki Shigemi ◽  
Mitsuhiko Kidogawa ◽  
Kinya Ishibashi ◽  
Kei Sugimoto
Keyword(s):  
Ultimate Strength ◽  
Bending Moment ◽  
Lateral Loads ◽  
Hull Girder ◽  
Local Strength ◽  
The Difference ◽  
Collapse Behavior ◽  
Large Container ◽  
Vertical Bending Moment

It is known that the hull girder ultimate strength with consideration of lateral loads such as bottom sea pressures and/or cargo loads generally decreases than that without consideration of the lateral loads (i.e. the effect of lateral loads). In this study a series of elasto-plastic analyses of three cargo holds models, which can reproduce the collapse behavior of the hold structures subjected to both vertical bending moment and lateral loads such as bottom sea pressures, container cargo loads etc., were carried out on a number of container ships with various sizes, and the hull girder ultimate strength obtained through the analyses were comparatively examined focusing on the effect of the lateral loads. As results of the examination, it has been concluded that local strength of the double bottom structure against the lateral loads is closely related to the hull girder ultimate strength in the case of container ships, the effect of the lateral loads on the hull girder ultimate strength varies among container ships due to the difference of construction of the double bottom structure and it is important to assess the hull girder ultimate strength explicitly taking into consideration the effect of the lateral loads for large container ships such as Post-Panamax sizes.

Determination of global design loads for large high-speed catamarans

2002 ◽  
Vol 216 (1) ◽  
pp. 79-94
Author(s):  
S E Heggelund ◽  
T Moan ◽  
S Oma
Keyword(s):  
High Speed ◽  
Bending Moment ◽  
Wave Loads ◽  
Strip Theory ◽  
Non Linear ◽  
Design Loads ◽  
Linear Effects ◽  
Operational Criteria ◽  
Vertical Bending Moment

Methods for calculation of design loads for high-speed vessels are investigated. The influence of operational restrictions on design loads is emphasized. Relevant operational criteria for high-speed displacement vessels are discussed. Procedures and criteria for numerical calculation of operational limits are incomplete and should be further investigated. Operational limits and design loads for a 60 m catamaran are calculated on the basis of linear strip theory. Non-linear effects on design loads are assessed from calculations in regular waves. Simplified formulae commonly used by classification societies for prediction of operational limits seem to over-predict the reduction of motions and wave loads at reduced speed. When operational limits typically given by the shipmaster or the operator are used, the design loads found by direct calculations are comparable with design loads given by classification societies. For vertical bending moment and torsion, the use of active foils is found to increase the linear loads. Owing to reduced motions, the foils reduce the non-linear loads and hence the total loads. The effect of non-linear horizontal loads is not investigated but can be important for transverse bending moment.

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.

Full-Scale Measurements on Hull Response of a Large-Container Ship in Service

2006 ◽  
Author(s):  
Kenichiro Miyahara ◽  
Ryuju Miyake ◽  
Norikazu Abe ◽  
Atsushi Kumano ◽  
Masanobu Toyoda ◽  
...  
Keyword(s):  
High Harmonic ◽  
Bending Moment ◽  
Full Scale ◽  
Linear Wave ◽  
Container Ship ◽  
Wave Loads ◽  
Non Linear ◽  
Large Container ◽  
Probability Density Distributions

In order to investigate hull responses of post-Panamax container ships in the actual sea, full-scale measurements on hull responses of a post-Panamax container ship in service were conducted. In linear wave domain, the probability density distributions of hull responses obtained by full-scale measurements were compared with the Rayleigh distributions to check on the range of the applicability, and comparisons with the long-term distributions of the longitudinal stress obtained by full-scale measurements and the direct structural analyses based on the wave loads analyzed by using the linear 3D Rankine source method were made to verify the accuracy. In non-linear wave domain, the measured longitudinal stresses showed the asymmetry of vertical bending moment. The long-term distributions of hull responses, which have the high harmonic components, obtained by full-scale measurements were compared with the numerical results analyzed by using non-linear methods to investigate the non-linearity on hull responses of container ship.

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