Springing Responses Analysis and Segmented Model Testing on a 550,000 DWT Ore Carrier

For ultra large ore carriers, springing response should be analyzed in the design stage since springing is the steady-state resonant vibration and has an important effect on the fatigue strength of hull structure. The springing response of a 550,000 DWT ultra large ore carrier has been studied by using experimental and numerical methods. A flexible ship model composed of nine segments was used in the experiment. The model segments were connected by a backbone with varying section, which can satisfy the request of natural frequency and stiffness distribution. The experiments in regular waves were performed and the motions and wave loads of the ship were measured. The experimental results showed that springing could be excited when the wave encounter frequency coincides with half or one-third the flexural natural frequency of the ship. In this paper, the analysis of the hydroelastic responses of the ultra large ore carrier was also carried out using a 3-D hydroelastic method. Comparisons between experimental and numerical results showed that the 3-D hydroelastic method could predict the motions and the vertical bending moments quite well. Based on this numerical method, the fatigue damage was estimated and the contribution of springing was analyzed.

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THE INFLUENCE OF CENTRE BOW LENGTH ON SLAMMING LOADS AND MOTIONS OF LARGE WAVE-PIERCING CATAMARANS

The International Journal of Maritime Engineering ◽

10.5750/ijme.v160ia1.1047 ◽

2021 ◽

Vol 160 (A1) ◽

Author(s):

J R Shahraki ◽

G A Thomas ◽

M R Davis

Keyword(s):

Wave Height ◽

Full Scale ◽

Bending Moments ◽

Regular Waves ◽

Large Wave ◽

Towing Tank ◽

Segmented Model ◽

Model Experiments ◽

Slamming Load ◽

Wave Induced

The effect of various centre bow lengths on the motions and wave-induced slamming loads on wave-piercing catamarans is investigated. A 2.5 m hydroelastic segmented model was tested with three different centre bow lengths and towed in regular waves in a towing tank. Measurements were made of the model motions, slam loads and vertical bending moments in the model demi-hulls. The model experiments were carried out for a test condition equivalent to a wave height of 2.68 m and a speed of 20 knots at full scale. Bow accelerations and vertical bending moments due to slamming showed significant changes with the change in centre bow, the longest centre bow having the highest wave-induced loads and accelerations. The increased volume of displaced water which is constrained beneath the bow archways is identified as the reason for this increase in the slamming load. In contrast it was found that the length of centre bow has a relatively small effect on the heave and pitch motions in slamming conditions.

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Experimental Study on Wave Loads of Flooded Ship

Volume 2: Structures, Safety and Reliability; Petroleum Technology Symposium ◽

10.1115/omae2007-29154 ◽

2007 ◽

Author(s):

B. W. Kim ◽

D. C. Hong ◽

S. Y. Hong ◽

J. H. Kyoung ◽

S. K. Cho ◽

...

Keyword(s):

Model Test ◽

Ship Motions ◽

Test Model ◽

Bending Moments ◽

Wave Loads ◽

Test Results ◽

Ocean Engineering ◽

Shear Forces ◽

Engineering Research ◽

Ship Model

This paper investigates wave loads of a flooded ship by model test. Model tests are performed in ocean engineering basin of MOERI (Maritime and Ocean Engineering Research Institute). Ship motions are measured by RODYM6D. Wave loads such as shear forces, bending moments and torsion moments are measured by ATI load cell mounted on segmented parts of the ship model. A 300 m-long barge ship with two flooded compartments is considered in model test. Responses of intact and flooded cases are compared. The test results are also compared with numerical analyses using boundary element method.

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Theoretical and Experimental Study on Nonlinear Hydroelastic Responses and Slamming Loads of Ship Advancing in Regular Waves

Shock and Vibration ◽

10.1155/2018/2613832 ◽

2018 ◽

Vol 2018 ◽

pp. 1-26 ◽

Cited By ~ 2

Author(s):

Jialong Jiao ◽

Yulin Zhao ◽

Yufei Ai ◽

Chaohe Chen ◽

Tianhui Fan

Keyword(s):

High Speed ◽

Large Scale ◽

Irregular Waves ◽

Green Water ◽

Design Stage ◽

Regular Waves ◽

Restoring Force ◽

Wave Basin ◽

Hull Structure ◽

Hydrodynamic Wave

Wave loads estimation and structural strength evaluation are the fundamental work at the ship design stage. The hydroelastic responses and slamming strength issues are also concerned especially for large-scale high-speed ships sailing in harsh waves. To accurately predict the wave-induced motions and loads acting on the ship sailing in regular waves, a fully coupled 3D time-domain nonlinear hydroelasticity theory is developed in this paper. The vibration modal characteristics of the flexible hull structure derived by the 3D finite element method (FEM) and simplified 1D nonuniform Timoshenko beam theory are firstly described. The hydrostatic restoring force and hydrodynamic wave force are calculated on the real-time wetted surface of hull to address geometric nonlinearity due to the steep wave and large amplitude motions. The bow slamming and green water loads acting on the ship in severe regular waves are estimated by the momentum impact method and dam-breaking method, respectively. Moreover, a small-scaled segmented ship model is designed, constructed, and tested in a laboratory wave basin to validate the hydroelasticity algorithm. The results predicted by theoretical and experimental approaches are systemically compared and analyzed. Finally, future work for predictions of ship hydroelasticity and slamming loads in irregular waves is prospected.

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The Influences of Centre Bow Length on Slamming Loads and Motions of Large Wave-Piercing Catamarans

10.3940/rina.ijme.2018.a1.451 ◽

2018 ◽

Vol Vol 160 (A1) ◽

Cited By ~ 1

Author(s):

J R Shahraki ◽

G A Thomas ◽

M R Davis

Keyword(s):

Wave Height ◽

Full Scale ◽

Bending Moments ◽

Regular Waves ◽

Large Wave ◽

Towing Tank ◽

Segmented Model ◽

Model Experiments ◽

Slamming Load ◽

Wave Induced

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Symmetric Response of a Hydroelastic Scaled Container Ship Model in Regular and Irregular Waves

Volume 4B: Structures, Safety and Reliability ◽

10.1115/omae2014-23860 ◽

2014 ◽

Cited By ~ 1

Author(s):

Sheng Peng ◽

Pandeli Temarel ◽

S. S. Bennett ◽

Weiguo Wu ◽

Zhengguo Liu ◽

...

Keyword(s):

Full Scale ◽

Irregular Waves ◽

Container Ship ◽

Bending Moments ◽

Segmented Model ◽

Numerical Predictions ◽

Hull Structure ◽

Strip Theory ◽

Head Waves ◽

Wave Induced

Wave-induced vibrations, such as whipping and springing, of container carriers have been attracting much attention because of their effects on hull-girder bending moments and fatigue damage. An investigation has been carried out comparing experimental measurements and numerical predictions of symmetric wave-induced loads (i.e. vertical bending moment) of the latest River-sea link container ship design, LPP = 130 m. The dual mission characteristics, namely rivers and open seas, make this type of ship an extremely interesting type of container carrier, particularly in terms of springing and whipping. A backbone beam segmented model is used in the experiments with the focus on springing- and whipping-induced vertical bending moments, for the model travelling at Fn = 0.21 in regular and long-crested irregular head waves, of 2.5m full-scale height or significant wave height. In addition higher order (harmonics) vertical bending moments (VBM) are also extracted from the experiments. The measurements are taken at amidships and the fore and aft quarters. Numerical predictions, for both the full-scale vessel and segmented model, are obtained using the two-dimensional linear hydroelasticity theories, where the hull structure is idealized as a non-uniform beam and the fluid actions evaluated using strip theory. The measured model test results, in relatively moderate conditions based on a particular area of operation for this low-draught vessel, indicate that nonlinear springing accounts for a significant portion of the total wave-induced bending moments in regular and, to an extent, irregular waves and slamming effects are small due to the operational area selected. The numerical predictions in regular waves show that linear hydroelasticity analysis can only predict similar trends in the variation of the VBM and the resonance peak. On the other hand, in long crested irregular waves the linear hydroelasticity analysis provides peak statistics that are commensurate with the measurements. The numerical predictions were obtained for two variants, having L = LPP and L = 0.9 LPP, the latter corresponding to the length of the backbone.

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Numerical Methods for Hull Structure Strength Analysis and Ships Service Life Evaluation, for a LPG Carrier

Volume 2: Structures, Safety and Reliability ◽

10.1115/omae2008-57602 ◽

2008 ◽

Author(s):

Leonard Domnisoru ◽

Dumitru Dragomir ◽

Alexandru Ioan

Keyword(s):

Service Life ◽

Dynamic Response ◽

Ship Hull ◽

Design Stage ◽

Head Wave ◽

Strength Analysis ◽

Response Analysis ◽

Wave Loads ◽

Life Evaluation ◽

Hull Structure

In this paper the authors focus on the ship hull structure strengths and fatigue analyses, in order to estimate the ship service life period at the initial design stage. The topic of the paper is divided in three-interlinked parts. The first part includes the method for the hull strength analysis, based on 3D/1D-FEM models, under equivalent quasi-static head wave loads. The second part presents the method for the ship hull dynamic response analysis, based on non-linear hydroelasticity theory with second order wave spectrum. The last part includes the fatigue analysis method for the initial ship hull structure, based on the long-term prediction ship dynamic response, the cumulative damage ratio and the design S-N material curves. The numerical analyses are carried out for a LPG carrier with independent cargo-tanks type A. Two significant load cases are considered: full and ballast. The numerical results outline the extreme wave loads and the ships initial service life evaluation.

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Hull Deformation Effect on Membrane-Type LNG Containment Systems

Volume 3: Structures, Safety and Reliability ◽

10.1115/omae2016-54903 ◽

2016 ◽

Author(s):

Bo Wang ◽

Yung-Sup Shin ◽

Eric Norris

Keyword(s):

Structural Integrity ◽

Water Pressure ◽

Local Deformation ◽

Fatigue Tests ◽

Wave Loads ◽

Insulation System ◽

Structural Fatigue ◽

Hull Structure ◽

Membrane Type ◽

Global Deformation

The objective of this study is to investigate the relationship between the maximum allowable hull deformation, which includes global elongation and local deflection, and the capacity of the CCS in membrane-type LNG vessels. The LNG CCS mainly consists of the primary barrier (e.g. a corrugated membrane for GTT MK III system and an invar membrane for GTT NO 96 system) and the insulation panel which is attached to the inner hull through mastics or couplers. The excessive hull elongation due to dynamic wave loads may cause fatigue damage of the primary barrier. Thus, the maximum allowable hull elongation (global deformation) can be determined based on the fatigue strength of the primary barrier. On the other hand, the excessive hull deflection due to cargo or ballast water pressure may cause failure of the insulation panel and the mastic. Therefore, the maximum allowable hull deflection (local deformation) in the hull design can be determined based on the strength of the insulation panel and the mastic. In the present paper, the determination of fatigue life vs. strain curves of materials has been summarized for the primary barrier. Fatigue curves based on either structural fatigue tests or standard specimen tests can be applied in fatigue assessment of a primary barrier. As an example, the finite element (FE) analysis has been conducted on the MK III CCS with the hull structure under pressure loads. Two different load cases including full load and ballast load conditions have been considered to evaluate the structural integrity of the insulation system in numerical simulations. FE results show that the mechanical behavior of the insulation system and the mastic under the maximum allowable hull deflection has been examined based on the yielding strength of each individual component. Finally, the complete procedure to determine the maximum allowable hull elongation and the maximum allowable hull deflection has been developed for meeting the requirements of containment system design for membrane-type LNG carriers.

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Vertical wave loads acting on a cruise ship in head, oblique and following regular waves

Progress in the Analysis and Design of Marine Structures ◽

10.1201/9781315157368-5 ◽

2017 ◽

pp. 29-34

Author(s):

S. Rajendran ◽

C. Guedes Soares

Keyword(s):

Wave Loads ◽

Cruise Ship ◽

Regular Waves

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INFLUENCE OF INCONSTANT DISTRIBUTION OF DEADWOOD BEARING STIFFNESS COEFFICIENTON NATURAL FREQUENCY OF THE SHAFT TRANSVERSE VIBRATIONS

VESTNIK OF ASTRAKHAN STATE TECHNICAL UNIVERSITY SERIES MARINE ENGINEERING AND TECHNOLOGIES ◽

10.24143/2073-1574-2019-1-89-96 ◽

2019 ◽

pp. 89-96

Author(s):

Guriy Kushner ◽

Victor Andreevich Mamontov

Keyword(s):

Differential Equation ◽

Distribution Function ◽

Uniform Distribution ◽

Natural Frequency ◽

Stiffness Coefficient ◽

Propeller Shaft ◽

Shaft Length ◽

Slide Bearing ◽

Transverse Vibrations ◽

Stiffness Distribution

One of the most significant factors affecting the natural frequency of transverse vibrations of shaft-slide bearing systems is the stiffness coefficient of the slide bearing. The need to consider the influence of heterogeneity of stiffness coefficient of the bearing on its natural frequency is caused by the fact that when the bearing is worn, the modulus of longitudinal elasticity of the material changes, and since the bearing wears unevenly, the non-uniform distribution of the stiffness coefficient occurs. The problem of determining the natural frequency of transverse vibrations of a ship propeller shaft based on the foundation with a variable stiffness coefficient along the length has been studied. The differential equation of the propeller shaft vibrations written taking into account the stiffness coefficient variable along the shaft length is considered. It has been noted that, in the general case, this equation is a fourth-order partial differential equation and cannot be integrated in quadratures for an arbitrary stiffness distribution function along the shaft length. A numerical-analytical method for determining the natural frequency of a system based on approximation of the stiffness distribution function by a piecewise-linear function is proposed. The method is applied to calculate the natural frequencies of the pipeline section taking into account the functions describing the change in the stiffness coefficient. The proposed method allows to consider the section of the shafting enclosed in the stern bearing, subject to the non-uniform distribution of the stiffness coefficient of the bearing, and is the basis for improving the accuracy of finding the true natural frequency of transverse vibrations of the shafting.

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