Hydroelastic Analysis of the Bending-Torsional Coupling Vibrations of an Ultra-Large Container Ship

2020 ◽  
Author(s):  
Hui Li ◽  
Lin Lu
Keyword(s):  
Resonance Phenomenon ◽  
Response Analysis ◽  
Container Ship ◽  
Hull Structure ◽  
Torsional Coupling ◽  
The Difference ◽  
Dynamic Amplification ◽  
Actual Response ◽  
Large Container ◽  
Wave Induced

Abstract Springing is a resonance phenomenon between the waves and the ship hull, and the high frequency vibration will threaten the safety of hull structures. With the development of economy, the size of ultra large container ships has been increasing, and the resulting springing and whipping response and their effects has been paid more and more attention. The structure of an ultra large container ship is essentially U-shaped with a low shear center, which results in strong coupling between horizontal bending and torsion. On the other hand, the actual response of hull structures will have an apparently dynamic amplification phenomenon under the effect of springing. In this paper, the wave-induced loads on the hull structure is estimated in the framework of the 3D linear hydroelastic theory, which coupling horizontal and torsional vibration. The vibration characteristics are investigated by using finite element method (FEM), which can get a better calculation accuracy than the simplified calculation method such as the Transfer Matrix Method. And the mode shape of displacement and section loads of the whole ship can be obtained and processed, which is needed for the analysis of hydroelasticity. Finally, in order to consider the effect of the dynamic amplification effect, the dynamic response analysis approach is used for the stress calculation. A 21000TEU is calculated by this method, and the difference between wave-induced and springing-induced section load in frequency domain is shown. Then the results of the frequency response analysis is compared with the quasi-static methods. And the effect of the springing and the dynamic magnification is analyzed.

scholarly journals Sloshing Impact Response in LNG Membrane Carriers: A Response Analysis of the Hull Structure Supporting the Membrane Tanks

2016 ◽  
Author(s):  
Jonas W. Ringsberg ◽  
André Liljegren ◽  
Ola Lindahl
Keyword(s):  
Structural Response ◽  
Response Analysis ◽  
Impact Loads ◽  
Dynamic Amplification Factor ◽  
Insulation System ◽  
Load Duration ◽  
Hull Structure ◽  
Load Characteristics ◽  
Membrane Type ◽  
Dynamic Amplification

This study presents the determination of structural response due to sloshing impact loads in LNG carriers with membrane type cargo tanks. These loads are characterized by very short durations and are thus likely to inflict a dynamic amplification in the response of the hull. Finite element analyses are presented using a model representing parts of an LNG membrane tank. The objective was to find and quantify the dynamic amplification factor (DAF) for the structural response towards sloshing impact pressures. The influence of variations in the load characteristics such as load duration, extent of the loaded area, load location as well as the influence of the insulation system was evaluated. The study shows that the response in the studied region of the hull structure experiences significant levels of dynamic amplification during impact loads with specific durations. The response sensitivity analysis also shows that the insulation system (MARK III type) has a large effect on the dynamic behaviour of the hull structure. It has been found to alter the magnitude of the stress and deflection response for key structural members. It also changes the load time durations for which the maximum dynamic amplification occurs and increases the magnitude of the corresponding response DAF. Finally, it has been found that dynamic response gives DAF values of up to 2. The effects have been found to be present for temporal load characteristics commonly occurring in sloshing model tests and full-scale measurements and are therefore likely to occur for a vessel in operation.

A Study on Forced Vibration of Double Bottom Structure due to Whipping on an Ultra Large Container Ship

2017 ◽  
Author(s):  
Yohei Kawasaki ◽  
Tetsuo Okada ◽  
Hiroaki Kobayakawa ◽  
Ichiro Amaya ◽  
Tetsuji Miyashita ◽  
...  
Keyword(s):  
Ultimate Strength ◽  
Time Domain ◽  
Forced Vibration ◽  
Wave Frequency ◽  
Container Ship ◽  
Hull Girder ◽  
Vibratory Response ◽  
Bottom Structures ◽  
Large Container ◽  
Wave Induced

Worldwide expansion of economy has brought about prominent and rapid enlargement of container ships. Their greater beam has caused more flexible double bottom structure, giving rise to concerns about its adverse effect to the ultimate strength of hull girder. To accurately assess the ultimate strength of hull girder, it is essential to precisely grasp how the double bottom structures behave in the actual sea state, in terms of whipping and vibratory response as well as wave frequency response. In this paper, the authors investigated structural behavior of the double bottom of a 14,000 TEU ultra large container ship in long-crested irregular head seas. Firstly, time domain ship motion and wave pressure on the hull surface was obtained through numerical analysis using Rankine source method. Subsequently, the obtained loads were applied to 3-dimensional whole ship finite element model, and time domain elastic responses of all over the hull structures were analyzed using Newmark-β method in terms of both whipping and wave frequency responses. As a result, regarding the wave frequency response, it was found that maximum wave induced upward bending of the midship double bottom structures is exerted almost simultaneously with the maximum wave induced hogging hull girder bending moment. The correlation factors between the double bottom bending and the hull girder bending were about 0.94 around the midship region, and they decreased in the fore and aft region. Regarding the whipping and vibratory response, it was found that large whipping response induces forced vibration of the double bottom structures, especially in the midship region. Because of the higher natural frequencies of the double bottom structures compared with that of whipping, the double bottom structures are excited in the same phase as the hull girder whipping, resulting in superimposed longitudinal stresses in way of the bottom shell plating. From these observations, it can be concluded that the local bending behavior of the double bottom structures adversely affects the hull girder ultimate strength, both in terms of wave loads and whipping loads, and it is necessary to take sufficient care to the double bottom rigidity.

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

2014 ◽  
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.

Structural Brittle Crack Arrest Design for Ultra Large Container Ship

2012 ◽  
Vol 81 (6) ◽  
pp. 485-488
Author(s):  
Masanobu TOYODA ◽  
Tsunehisa HANDA
Keyword(s):  
Crack Arrest ◽  
Container Ship ◽  
Brittle Crack ◽  
Large Container

Dynamic Response Analysis of Butt Joint of HTS-A Steel Considering Welding Residual Stresses

2013 ◽  
Vol 423-426 ◽  
pp. 944-950
Author(s):  
Wei Shen ◽  
Ren Jun Yan ◽  
Lin Xu ◽  
Kai Qin ◽  
Xin Yu Zhang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Dynamic Response ◽  
Hot Spot ◽  
Time History ◽  
High Strength ◽  
Simulation Method ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Response Analysis ◽  
Hull Structure

This paper uses both numerical simulation method and experimental research method to study on welding residual stress of high-strength steel of the cone-cylinder hull. Welding is often accompanied by a larger welding residual stress, which directly affects the safety and service life of the hull structure. In order to obtain the distribution of the welding residual stress, the welding procedure was developed by its parameter language by using FE analysis software in this paper. Then the welding residual stress of hot spot region was measured through X-ray nondestructive testing method, and compared it with simulation results. Finally, considering the residual stress as the initial stress, this paper analyzed dynamic response process of the welding structure under combined actions of the welding residual stress and multiaxial loads, which could more accurately determine the stress of welding structure and the location of fatigue risk point. According to the amplitude of damage parameters and strain time-history curve, we can estimate the fatigue life of structure by selecting the corresponding damage models.

FATIGUE RELIABILITY ASSESSMENT OF WELDED JOINTS OF VERY FAST FERRY ACCOUNTING FOR VEHICLE LOADS

2021 ◽  
Vol 153 (A4) ◽  
Author(s):  
Y Garbatov ◽  
C Guedes Soares
Keyword(s):  
Hot Spots ◽  
Reliability Assessment ◽  
Stress Distributions ◽  
Structural System ◽  
Fatigue Reliability ◽  
Welded Steel ◽  
Longitudinal Stiffener ◽  
Hull Structure ◽  
Vehicle Loads ◽  
Wave Induced

This work deals with the fatigue reliability assessment of a welded joint in a longitudinal stiffener of trapezoidal shape in a very fast ferry. Based on the analysis of wave and cargo induced loads the ship hull structure is evaluated. The local structure is represented by a longitudinal stiffener with a trapezoidal transverse section. The critical hot-spots and the stress distributions are defined by FEM. The fatigue damage assessment of considered hot spots is analysed accounting for the combination of wave induced and car-breaking transient loadings. The formulation for the assessment of the welded steel joint is based on the S-N approach and FORM/SORM techniques are applied to evaluate the reliability against fatigue failure accounting for corrosion deterioration. The structural system composed by several hot spots is evaluated as a series system based on second order reliability bounds.

The Effect of Bow Shape on the Springing/Whipping Response of a Large Ocean-Going Vessel: Investigated by an Experimental Method

2007 ◽  
Author(s):  
Gaute Storhaug ◽  
Torgeir Moan
Keyword(s):  
Fatigue Damage ◽  
Transfer Functions ◽  
Vertical Vibration ◽  
Full Scale ◽  
Relative Importance ◽  
High Frequency Response ◽  
Bow Flare ◽  
Excitation Mechanisms ◽  
The Difference ◽  
Wave Induced

Wave induced vibrations often referred to as springing and/or whipping increase the fatigue and extreme loading in ship hull girders. Both effects are disregarded in current ship rules. Various numerical codes exist for predicting the wave induced vibrations, but so far they are not considered reliable. Another means to investigate the importance of the high frequency response, although more resource demanding, is to carry out full scale measurements and/or model tests. Recently, full scale measurements of blunt ships have been carried out by DNV, and in this paper one of these ships was considered and tested in a towing tank to evaluate the additional fatigue damage due to the wave induced vibrations. Different excitation sources may excite the 2-node vertical vibration mode depending on ship design, and it is not straight forward to determine which is more important. The relative importance of the excitation mechanisms are investigated by two approaches in this paper. The first approach separates the whipping from springing to illustrate their relative importance based on basic theory in combination with model test results. The linear and second order transfer functions are utilized in this procedure. The second approach deals with the effect of the bow design on the additional fatigue damage. Three different bows were tested. The first bow design is identical to the real ship. The second bow design is a simplified version of the first one, by removing the bulb and flare. The third bow is fundamentally different from the two former blunt bows. Bow three is sharp pointed with a vertical sharp stem and vertical ship sides. The results indicate that the importance of whipping depends on the sea state, but that it is of similar importance as springing for the sea states that contributes most to the fatigue damage. Moreover, the difference in the additional fatigue damage due to wave induced vibrations for different bow shapes is moderate. This indicates that vessels with pointed bows and without pronounced bow flare, such as LNG vessels, may have a similar contribution from wave induced vibrations. Modern container vessels, which are more slender, but with pronounced bow flares should be further investigated.

scholarly journals Nonlinear bending moments of an ultra large container ship in extreme waves based on a segmented model test

2022 ◽  
Vol 243 ◽  
pp. 110335
Author(s):  
Ying Tang ◽  
Shi-Li Sun ◽  
Rui-Song Yang ◽  
Hui-Long Ren ◽  
Xin Zhao ◽  
...  
Keyword(s):  
Model Test ◽  
Container Ship ◽  
Bending Moments ◽  
Extreme Waves ◽  
Nonlinear Bending ◽  
Segmented Model ◽  
Large Container
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