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

2007 ◽  
pp. 2786-2789
Author(s):  
Chao He Chen
Keyword(s):  
Linear Wave ◽  
Wave Loads ◽  
Ship Structure ◽  
Fatigue Assessment ◽  
Non Linear

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

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.

Advanced Integrated Design Method for Fatigue Assessment of Large Elastic Ship Structures

2013 ◽  
Vol 371 ◽  
pp. 443-447
Author(s):  
Ionica Rubanenco ◽  
Iulia Mirciu ◽  
Leonard Domnisoru
Keyword(s):  
Service Life ◽  
Hot Spot ◽  
Ratio Method ◽  
Wave Loads ◽  
Ship Structures ◽  
Fatigue Assessment ◽  
Integrated Method ◽  
Oscillation Analysis ◽  
Non Linear ◽  
Wave Induced

This paper is focused on an advanced method for ship structures fatigue assessment. The ships classification societies standard rules for fatigue analysis are based on simplified procedures, with wave induced loads obtained by linear oscillation analysis (low frequency, around 0.1 Hz), or equivalent statistical wave loads. In the case of large elastic ship structures, with hull length over 150 m, the global wave induced vibration response (high frequency, around 1 Hz) becomes significant. The developed integrated method for large ships fatigue assessment includes three interlinked analyses, as follows: the hot-spot stresses evaluation by 3D finite element models, wave induced loads by short term linear and non-linear hydroelastic dynamic analysis, ship service life and fatigue assessment by damage cumulative ratio method. As testing ship, it is considered a double hull LPG Liquefied Petroleum Gas carrier, with total length 239 m, for a set of structural details with stress hot-spots. Based on the non-linear hydroelastic wave loads, the integrated method of fatigue assessment becomes more accurate, predicting for the amidships structure 14 years of ship service life, instead of over 20 years according to the rules standard approach, so that the confidence on ship structure fatigue evaluation can be increased in the design process.

Non-linear wave loads and ship responses by a time-domain strip theory

1998 ◽  
Vol 11 (3) ◽  
pp. 101-123 ◽  
Author(s):  
Jinzhu Xia ◽  
Zhaohui Wang ◽  
J.Juncher Jensen
Keyword(s):  
Time Domain ◽  
Linear Wave ◽  
Wave Loads ◽  
Strip Theory ◽  
Non Linear

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.

Non-Linear Wave Loads Acting on Obliquely Slowly Advancing Platform

2009 ◽  
Author(s):  
Yasunori Nihei ◽  
Sota Sugimoto ◽  
Takashi Tsubogo ◽  
Weiguang Bao ◽  
Takeshi Kinoshita
Keyword(s):  
Boundary Value Problems ◽  
Potential Theory ◽  
Boundary Value ◽  
The Body ◽  
Linear Wave ◽  
Wave Loads ◽  
Forward Speed ◽  
Wave Drift ◽  
Non Linear ◽  
Drift Force

It is necessary to evaluate wave drift force for ships advancing obliquely. There are some approaches, for instance the strip method, solving the Navier-Stokes equation directly in the fluid domain (CFD), potential theory and so on. In the present study, the non-linear wave loads acting on the ship with constant oblique forward speed is considered based on the potential theory. Consistent perturbation expansion based on two parameters, i.e. the incident wave slope and the ratio of the forward speed compared to the phase velocity of the waves, is performed on a moving frame (body-fixed) coordinate system to simplify the problem. So obtained boundary value problems for each order of potentials is solved by means of the hybrid method. The fluid domain is divided into two regions by an artificial circular cylinder surrounding the body. The potential in the inner region is expressed by an integral over the boundary surface with a Rankin source as its Green function while it is expressed in the eigen function expansion for the outer region. Consequently, the boundary value problems can be solved efficiently. In the present paper, the authors will discuss the effects of the obliquely advancing on the wave drift force in a diffraction wave field up to the order proportional to the advancing speed. An ellipsoid model is used in the calculation and the wave drift force is evaluated for various Froude number.

Non-Linear Wave Forces Acting on a Body of Arbitrary Shape Slowly Oscillating in Waves

2005 ◽  
Author(s):  
Yasunori Nihei ◽  
Takeshi Kinoshita ◽  
Weiguang Bao
Keyword(s):  
Low Frequency ◽  
The Body ◽  
Coordinate Frame ◽  
Wave Forces ◽  
Linear Wave ◽  
Wave Loads ◽  
Low Frequency Oscillation ◽  
Wave Drift ◽  
Non Linear ◽  
Low Frequency Motion

In the present study, non-linear wave loads such as the wave drift force, wave drift damping and wave drift added mass, acting on a moored body is evaluated based on the potential theory. The body is oscillating at a low frequency under the non-linear excitation of waves. The problem of interaction between the low-frequency oscillation of the body and ambient wave fields is considered. A moving coordinate frame following the low frequency motion is adopted. Two small parameters, which measure the wave slope and the frequency of slow oscillations (compared with the wave frequency) respectively, are used in the perturbation analysis. So obtained boundary value problems for each order of potentials are solved by means of the hybrid method. The fluid domain is divided into two regions by an virtual circular cylinder surrounding the body. Different approaches, i.e. boundary element method and eigen-function expansion, are applied to these two regions. Calculated nonlinear wave loads are compared to the semi-analytical results to validate the present method.

New Methods to Solve High Order Potential Used in Calculating Non-Linear Wave Loads

2006 ◽  
Author(s):  
Yasunori Nihei ◽  
Weiguang Bao ◽  
Takeshi Kinoshita
Keyword(s):  
Perturbation Expansion ◽  
Low Frequency ◽  
The Body ◽  
Body Motion ◽  
Moving Frame ◽  
Linear Wave ◽  
Wave Loads ◽  
Wave Drift ◽  
Non Linear ◽  
Low Frequency Motion

In the present study, non-linear wave loads such as the wave-drift force, wave-drift damping and wave-drift added mass, acting on the body is considered based on the potential theory. To investigate non-linear wave loads, consistent perturbation expansion by means of two small parameters, i.e. the incident wave slope and the low frequency body motion, is performed on a moving frame (body-fixed) coordinate system. To avoid complicated free surface integrals as much as possible, new approach for the higher order potential in the interaction problem of low frequency motion and waves is suggested in the present work. Instead of integrals, derivative operators are defined to obtain special solutions efficiently.

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