A Two-Dimensional Hydroelastoplasticity Method of a Container Ship in Extreme Waves

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Weiqin Liu ◽  
Katsuyuki Suzuki ◽  
Kazuki Shibanuma
Keyword(s):  
Dynamic Response ◽  
Ultimate Strength ◽  
Nonlinear Dynamic ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Nonlinear Relationship ◽  
Container Ship ◽  
Two Dimensional ◽  
Extreme Waves ◽  
Wave Load

Extreme waves have led to many accidents and losses of ships at sea. In this paper, a two-dimensional (2D) hydroelastoplasticity method is proposed as a means of studying the nonlinear dynamic response of a container ship when traversing extreme waves, while considering the ultimate strength of the ship. On one hand, traditional ultimate strength evaluations are undertaken by making a quasi-static assumption and the dynamic wave effect is not considered. On the other hand, the dynamic response of a ship as induced by a wave is studied on the basis of the hydroelasticity theory so that the nonlinear structural response of the ship cannot be obtained for large waves. Therefore, a 2D hydroelastoplasticity method, which takes the coupling between time-domain waves and the nonlinear ship beam into account, is proposed. This method is based on an hydroelasticity method and a simplified progressive collapse method that combines the wave load and the structural nonlinearity. A simplified progressive collapse method, which considers the plastic nonlinearity and buckling effect of stiffened, is used to calculate the ultimate strength and nonlinear relationship between the bending moment and curvature, so that the nonlinear relationship between the rigidity and curvature is also obtained. A dynamic reduction in rigidity related to deformation could influence the strength and curvature of a ship's beam; therefore, it is input into a dynamic hydrodynamic formula rather than being regarded as a constant structural rigidity in a hydroelastic equation. A number of numerical extreme wave models are selected for computing the hydroelastoplasticity, such that large deformations occur and nonlinear dynamic vertical bending moment (VBM) is generated when the ship traverses these extreme waves. As the height and Froude number of these extreme waves are increased, a number of hydroelastoplasticity results including VBM and deformational curvature are computed and compared with results obtained with the hydroelasticity method, and then, some differences are observed and conclusions are drawn.

Strength of a Container Ship in Extreme Waves Obtained by Nonlinear Hydroelastoplasticity Dynamic Analysis and Finite Element Modeling

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Weiqin Liu ◽  
Xuemin Song ◽  
Weiguo Wu ◽  
Katsuyuki Suzuki
Keyword(s):  
Finite Element ◽  
Nonlinear Dynamic ◽  
Structural Response ◽  
Bending Moment ◽  
Dynamic Responses ◽  
Container Ship ◽  
Extreme Waves ◽  
Wave Models ◽  
The One ◽  
The Time Domain

Extreme waves have caused a lot of ship accidents and casualties. In this paper, a two-dimensional (2D) hydroelastoplasticity method is proposed to study the nonlinear dynamic responses of a container ship in extreme waves. On the one hand, the traditional ultimate strength evaluation is mainly performed using a quasi-static assumption without considering the dynamic wave effect. On the other hand, the dynamic response of a ship induced by a wave is studied based on hydroelasticity theory, which means the ship structural response to large waves is linear. Therefore, a 2D hydroelastoplasticity method that accounts for the coupling between the time-domain wave and ship beam for nonlinear vertical bending moment (VBM) is proposed. In addition, a nonlinear dynamic finite element method (FEM) is also applied for the nonlinear VBM of ship beam. The computational results of the FEM, including the nonlinear VBM and deformational angle, are compared with the results of the 2D hydroelastoplasticity and hydroelasticity. A number of numerical extreme wave models are selected for computations of hydroelasticity-plasticity, hydroelasticity, and FEM. A difference is observed between the nonlinear VBM calculated by FEM and linear VBM calculated by hydroelasticity, and conclusions are drawn.

Experimental Determination of the Ultimate Strength of Box Girder Specimens

2016 ◽  
Author(s):  
Thomas Lindemann ◽  
Patrick Kaeding ◽  
Eldor Backhaus
Keyword(s):  
Finite Element ◽  
Experimental Determination ◽  
Ultimate Strength ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Element Model ◽  
Experimental Results ◽  
Bending Test ◽  
Box Girder

The Finite Element Method (FEM) is a feasible tool to perform progressive collapse analyses of large structural systems. Despite enormous developments in finite element formulations and computer technologies the results of structural analyses should be validated against experimental results. In this paper the collapse behaviour of two identical box girder specimens is determined experimentally for the load case of pure longitudinal bending. The specimens are composed of stiffened plate panels and connected at either ends to a loading structure. Within a 4-point bending test a constant bending moment is applied to each specimen to determine the collapse behaviour even in the post-ultimate strength range. The results of the experimental determination of the ultimate strength are presented for the box girder specimens. To simulate the collapse behaviour a finite element model is used and validated against experimental results.

Numerical and Experimental Investigation on Nonlinear Cyclic Collapse Response of Ship Model in Regular Waves

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Weiqin Liu ◽  
Yu Huang ◽  
Ye Li ◽  
Xuemin Song ◽  
Fangyi Wei ◽  
...  
Keyword(s):  
Ultimate Strength ◽  
Nonlinear Dynamic ◽  
Dynamic Strength ◽  
Bending Moment ◽  
Bending Test ◽  
Wave Loads ◽  
Nonlinear Simulation ◽  
Ship Structure ◽  
Ship Model ◽  
Element Method

Abstract Large ocean waves with large wave height may destroy the ship’s structure, whereas it is difficult to predict the nonlinear dynamic strength in the large waves. In this study, we used a nonlinear simulation based on boundary element method (BEM)-finite element method (FEM) and a collapse experiment of ship model to study dynamic ultimate strength and dynamic course of collapse of ship structure, the collapse test was performed in regular tank wave. Besides, a simulation method for nonlinear dynamic ship strength was proposed to predict and compare the results of collapse test. A collapsed model consisting of a plastic hinge and two ship strips is designed. Subsequently, we performed the nonlinear simulation of the ultimate strength of ship model induced by tank wave. Wave loads were calculated following potential theory and BEM. Next, ship structural FEM model was modeled, the ship pressure was transferred to ship wet surface elements, and inertia force was exerted as well. Finally, the nonlinear dynamic strength calculation of ship model was performed in accordance with nonlinear FEM. A four-point-bending test adopted displacement controlling method was designed to obtain the hysteresis characteristic of the elastoplastic hinge. Hysteretic test and simulation analysis was performed to determine post-ultimate bending moment. Time-domain computational results including rotation angle history and vertical bending moment are close to collapse test results so that the two methods are verified. This study verifies that structural nonlinearities of ship structure induced by wave loads could be predicted.

scholarly journals Dynamic Response and Robustness Evaluation of Cable-Supported Arch Bridges Subjected to Cable Breaking

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Guotao Shao ◽  
Hui Jin ◽  
Ruinian Jiang ◽  
Yue Xu
Keyword(s):  
Dynamic Response ◽  
Evaluation Method ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Simulation Method ◽  
Dynamic Amplification Factor ◽  
Cable System ◽  
Evaluation Indexes ◽  
Dynamic Amplification ◽  
Arch Bridges

Cable-supported arch bridges have had many cable break accidents, which led to dramatic deck damage and even progressive collapse. To investigate the dynamic response and robustness of cable-supported arch bridges subjected to cable breaking, numerical simulation methods were developed, compared, and analyzed, and an effective and accurate simulation method was presented. Then, the cable fracture of a prototype bridge was simulated, and the dynamic response of the cable system, deck, and arch rib was illustrated. Finally, the robustness evaluation indexes of the cable system, deck, and arch rib were constructed, and their robustness was evaluated. The results show that the dynamic response of the adjacent cables is proportional to the length of the broken cable, while the dynamic response of the deck is inversely proportional to the length of the broken cable. The dynamic amplification factor of the cable tension and deck displacement is within 2.0, while that of the arch rib bending moment exceeds 2.0. The break of a single cable will not trigger progressive collapse. When subjected to cable breaking, the deck system has the least robustness. The proposed cable break simulation procedure and the robustness evaluation method are applicable to both existing and new cable-supported bridges.

Dynamic Ultimate Strength of a Container Ship Under Sagging Condition

2020 ◽  
Author(s):  
George Jagite ◽  
Hervé le Sourne ◽  
Patrice Cartraud ◽  
Fabien Bigot ◽  
Quentin Derbanne ◽  
...  
Keyword(s):  
Ultimate Strength ◽  
Dynamic Load ◽  
Research Work ◽  
Structural Response ◽  
Bending Moment ◽  
Container Ship ◽  
Wave Loads ◽  
Hull Girder ◽  
Load Factors ◽  
Collapse Effect

Abstract When technically specifying ships for the future, the following aspects are examples of what we will have even more focus on than today: bigger, lighter, and faster. Thereby, the hydro-elastic type of structural response will be more and more significant. In addition, some of the recent container ships’ designs are with very low values of the “minimum hogging still water bending moment.” Combined with high whipping induced sagging moments, it casts some doubts on the probability of buckling appearance in the upper structure. Therefore, the objective of the research work presented in this paper is to investigate the dynamic ultimate strength of the entire hull girder section, subjected to sagging bending moment associated with wave loads and whipping response. The dynamic ultimate strength is computed and compared with the quasi-static ultimate strength, in order to derive the dynamic load factors, which can be used as an estimator of the dynamic collapse effect.

Analysis Method of Ultimate Strength of Ship Hull Girder Under Combined Loads: Application to an Existing Container Ship

2016 ◽  
Author(s):  
Yoshiteru Tanaka ◽  
Yutaka Hashizume ◽  
Hiroaki Ogawa ◽  
Akira Tatsumi ◽  
Masahiko Fujikubo
Keyword(s):  
Ultimate Strength ◽  
Cross Section ◽  
Bending Strength ◽  
Progressive Collapse ◽  
Fem Analysis ◽  
Ship Hull ◽  
Strength Analysis ◽  
Container Ship ◽  
Hull Girder ◽  
Longitudinal Bending

A ship hull is regarded as a box girder structure consisting of plates and stiffeners. When the ship hull is subjected to excessive longitudinal bending moment, buckling and yielding of plates and stiffeners take place progressively and the ultimate strength of the cross-section is attained. The ultimate longitudinal bending strength is one of the most fundamental strength of a ship hull girder. Finite element method (FEM) analysis using fine-mesh hold models has been increasingly applied to the ultimate longitudinal strength analysis of ship hull girder. However, the cost and elapsed time necessary for FEM analysis including finite element modelling are still large for the design stage. Therefore, the so-called Smith’s method [1] has been widely employed for the progressive collapse analysis of a ship hull girder under bending. Recently, there is a growing demand for a container ship, which is characterized as a hull girder with large open decks. This type of ship has a relatively small torsional stiffness compared to the ships with closed cross-section and the effect of torsion on the ultimate longitudinal strength may be significant. However, the Smith’s method above mentioned cannot consider the influence of torsion. Therefore, some of the authors developed a simplified method of the ultimate strength analysis of a hull girder under torsion as well as bending [2–4]. In this method, a hull girder is modeled by linear beam elements in the longitudinal direction, and the warping as well as bending deformation is included in the formulation. The cross-section of a beam element is divided into plate elements by the same way as the Smith’s method. Therefore, the shift of instantaneous neutral axis and shear center can be automatically considered by introducing the axial degree of freedom as well as the bending ones into the beam elements, and keeping the zero axial load condition. In this study, the average stress-average strain relationship of each element is calculated using the formulae of the Common Structural Rules (CSR) [5] and HULLST proposed by Yao et al. [6, 7] considering the effect of shear stress due to torsion on the yield strength. There had been a lot of papers [8] which discuss the importance of strength assessment to large container ships under torsion. However, there are few papers which discuss the influence of torsion on the ultimate hull girder strength. In this paper, the proposed simplified method is applied to the existing Post-Panamax class container ship. First, a torsional moment is applied to the beam model for the ship within the elastic range. Then, the ultimate bending strength of cross-sections is calculated applying the Smith’s method to a beam element considering the warping and shear stresses. On the other hand, nonlinear explicit FEM are adopted for the progressive collapse analysis of the ship by using LS-DYNA. The effectiveness of present simplified analysis method of ultimate hull girder strength under combined loads is discussed compared with the LS-DYNA analysis.

Effect of current on the dynamic response of a bi-articulated offshore tower

2020 ◽  
Vol 23 (14) ◽  
pp. 3089-3101
Author(s):  
Mohd Moonis Zaheer ◽  
Nazrul Islam
Keyword(s):  
Dynamic Response ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Equations Of Motion ◽  
Bending Moment ◽  
Dynamic Effect ◽  
Random Wave ◽  
Wave Load ◽  
Environmental Loads ◽  
Power Spectral

Wind and wave loadings have a predominant role in the design of articulated offshore towers for its successful service and survival. Such towers are very sensitive to the dynamic effect of environmental loads. The compliant nature of these towers with environmental loads introduces geometric nonlinearity due to large displacements, which becomes an important consideration in the analysis of these towers. This article deals with the dynamic response of a bi-articulated offshore tower to wind, wave, and current forces. The exposed portion of the tower is subjected to the action of wind, while the submerged portion is acted upon by random wave and current forces. Wind load is modeled by Ochi and Shin spectrum, while the wave load is characterized by Pierson–Moskowitz spectrum. The nonlinear dynamic equations of motion are derived by Hamilton’s principle. Response of the tower is determined by a time domain iterative (Wilson-θ) method. Power spectral density of important parameters such as surge, tilting motion, hinge shear, and bending moment are presented under high and low sea states. It is observed that response of tower due to current modifies the peak energy of power spectral density functions.

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