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

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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Fatigue Assessment for Ship Structure Acted on Non-Linear Wave Loads

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.353-358.2786 ◽

2007 ◽

Vol 353-358 ◽

pp. 2786-2789

Author(s):

Chao He Chen

Keyword(s):

Fatigue Damage ◽

Bending Moment ◽

Linear Wave ◽

Wave Loads ◽

Ship Structure ◽

Random Seas ◽

Non Linear ◽

Bow Flare ◽

Short Term Prediction ◽

The Given

Efficient methods are described here to predict the fatigue damage of ship structure due to nonlinear wave loads that are produced in random seas. Firstly the effects of the non-linear waveinduced bending moment on the fatigue damage of ship structure with very large bow flare are presented in short-term prediction by the method of spectrum analysis. Then, the fatigue damage is estimated and analyzed in the given environment of long-term.

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Long-Term Fatigue Damage of Ship Structures Under Nonlinear Wave Loads

Marine Technology and SNAME News ◽

10.5957/mt1.2002.39.2.95 ◽

2002 ◽

Vol 39 (02) ◽

pp. 95-104

Author(s):

Xue KangGu ◽

Torgeir Moan

Keyword(s):

Fatigue Damage ◽

Nonlinear Wave ◽

Direct Analysis ◽

Linear Wave ◽

Wave Loads ◽

Ship Structures ◽

Hull Girder ◽

Structural Fatigue ◽

Large Container

Fatigue is a principal mode of failure in ship structures, especially when high tensile steels are applied. Although significant efforts have been made to predict fatigue damage, there are still uncertainties existing, e.g., in the stress histories that cause fatigue. This paper addresses estimation of fatigue damage in ships under wave loads, with an emphasis on containerships, which have large bow flare and low hull girder rigidity. Linear and nonlinear wave-induced loads as well as dynamic effects due to hull flexibility, i.e., whipping, are researched. With the direct analysis method of fatigue, the nature of the wave loading, hull rigidity, structural damping, stress range counting algorithm and SN curve on structural fatigue damage are investigated. In long-term fatigue damage estimates, the influence of different sea environments is numerically analyzed. The importance of nonlinearity of wave loads and especially the whipping on the structural fatigue damage is demonstrated by calculation for a large container vessel with large flare and lowest natural frequency of 0.749 Hz. Depending upon sea environments and SN curves used in long-term predictions, the fatigue damage based on nonlinear wave loads (excluding whipping) is 10–100% larger than that due to linear wave loads; the fatigue damage based on nonlinear combined loads (including whipping) may be 1–9 times larger than that of steady-state nonlinear wave loads.

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Fatigue Strength Assessment Analysis of Large Container Ship

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.602-605.385 ◽

2014 ◽

Vol 602-605 ◽

pp. 385-389 ◽

Cited By ~ 1

Author(s):

Feng Lei Han ◽

Chun Hui Wang ◽

An Kang Hu ◽

Ya Chong Liu

Keyword(s):

Fatigue Strength ◽

Hot Spot ◽

Direct Calculation ◽

Linear Wave ◽

Container Ship ◽

Wave Loads ◽

Wave Load ◽

Strength Assessment ◽

Fatigue Strength Assessment ◽

Large Container

Fatigue assessments of container ship structures can be processed using various direct calculation approaches or various approaches of classification societies [1,2]. In this investigation, the fatigue strength assessment to the key positions of a 9200TEU container ship has been performed ,subjected to the rules of BV about fatigue strength specification of large container ships, based on design wave method and Miner fatigue cumulative damage theory analysis method. Wave loads have been computed using linear wave load calculation method based on three-dimensional potential flow theory. And the fatigue strength assessment of the typical hot spot structures has also been conducted based on a series of critical single design wave.

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

Volume 4: Offshore Geotechnics; Ronald W. Yeung Honoring Symposium on Offshore and Ship Hydrodynamics ◽

10.1115/omae2012-83043 ◽

2012 ◽

Cited By ~ 2

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.

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Time Domain Analysis of Springing and Whipping Responses Acting on a Large Container Ship

Volume 6: Ocean Engineering ◽

10.1115/omae2011-49218 ◽

2011 ◽

Cited By ~ 1

Author(s):

Yongwon Lee ◽

Zhenhong Wang ◽

Nigel White ◽

Spyros E. Hirdaris

Keyword(s):

Time Domain ◽

Nonlinear Effects ◽

Time Domain Analysis ◽

Container Ship ◽

Wave Loads ◽

Ocean Engineering ◽

Hull Girder ◽

Engineering Research ◽

Large Container ◽

Element Method

As part of WILS II (Wave Induced Loads on Ships) Joint Industry Project organised by MOERI (Maritime and Ocean Engineering Research Institute, Korea), Lloyd’s Register has undertaken time domain springing and whipping analyses for a 10,000 TEU class container ship using computational tools developed in the Co-operative Research Ships (CRS) JIP [1]. For idealising the ship and handling the flexible modes of the structure, a boundary element method and a finite element method are employed for coupling fluid and structure domain problems respectively. The hydrodynamic module takes into account nonlinear effects of Froude-Krylov and restoring forces. This Fluid Structure Interaction (FSI) model is also coupled with slamming loads to predict wave loads due to whipping effects. Vibration modes and natural frequencies of the ship hull girder are calculated by idealising the ship structure as a Timoshenko beam. The results from springing and whipping analyses are compared with the results from linear and nonlinear time domain calculations for the rigid body. The results from the computational analyses in regular waves have been correlated with those from model tests undertaken by MOERI. Further the global effects of springing and whipping acting on large container ships are summarised and discussed.

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