Feasibility study on buoyancy–weight ratios of a submerged floating tunnel prototype subjected to hydrodynamic loads

Long, Xu; Ge, Fei; Hong, Youshi

doi:10.1007/s10409-015-0428-3

Cited by 20 publications

(7 citation statements)

References 22 publications

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“…Additionally, the vortex shedding frequency in the wake region around the tube is generally not close to the natural frequency of the tunnel. Additionally, because the vortex-induced force on the tunnel is much smaller than the wave loads and the restoring forces from the mooring system, in most cases aiming at the hydrodynamic response of SFT [6,8,9,11], only the wave forces on the tube are considered, without the vortex-induced force. Hence, we separately consider the wave force acting on the tube body, and the effect of water flow on the cables.…”

Section: Governing Equationsmentioning

confidence: 99%

“…Kunisu [7] used the boundary element method (BEM) and the Morison equation to calculate the wave load acting on the SFT. Long et al [8,9] studied the effects of some basic structure parameters on the dynamic behaviors of the SFT under wave and current via ANSYS software. Seo et al [10] measured the wave forces acting on the tunnel tube through a model test with scale SFT segments.…”

Section: Introductionmentioning

confidence: 99%

“…Most of the above research mainly addressed the global performance of the SFT tube based on Morison equations [7][8][9][10][11]. However, despite that the support stiffness provided by anchor-cables acting on the tube was included in most of these models, the vibration of the cable itself was neglected.…”

Section: Introductionmentioning

confidence: 99%

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Coupled Vibration Analysis of Submerged Floating Tunnel System in Wave and Current

et al. 2018

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Featured Application: A simplified theoretical model is proposed for vibration analysis of the coupled Submerged floating tunnel (SFT) tube-cable system under combined vortex-induced and wave forces. Several cases under different working conditions are presented to reveal the dynamic characteristics of the SFT. This approach can be extended to future actual structures to determine structural parameters and avoid strong resonance.Abstract: Submerged floating tunnel (SFT) is an innovative underwater structure for crossing long straits, which withstands the effects of water wave and current throughout its lifecycle. This paper proposes a theoretical approach to investigate the nonlinear dynamic response of the SFT tube-cable system under combined parametric excitation and hydrodynamic forcing excitations (i.e., wave and vortex-induced loading). Firstly, the governing equations of the SFT system considering the coupled degrees of freedom in the tube and cable are established based on the Hamilton principle and are solved numerically. Then, several representative cases are analyzed to reveal the dynamic characteristics of the SFT. Finally, some key parameters are discussed, such as the wave and current conditions and the structural parameters. The results show that when the flow velocity reaches a certain value, the vortex-induced vibration (VIV) of the anchor-cables will excite a strong resonance in the structure. The displacement amplitude of the SFT increases with the increase of the wave height. Gravity-buoyance ratio (GBR) of the tube and the inclined mooring angle (IMA) of the cables jointly determine the natural vibration frequency of the SFT. The influence of the wave force on the tube is limited when the installation depth of SFT is more than 40 m.

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Section: Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coupled Vibration Analysis of Submerged Floating Tunnel System in Wave and Current

et al. 2018

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“…Environmental loads include waves, earthquakes, currents, and tsunamis. Among them, waves tend to be the most important environmental loading if the submergence depth is not sufficiently large [3][4][5][6][7]. For SFT with a large diameter, it was found through hydro-elastic analysis that large static and dynamic mooring tensions were critical issues [7].…”

Section: Introductionmentioning

confidence: 99%

Mooring-Failure Monitoring of Submerged Floating Tunnel Using Deep Neural Network

et al. 2020

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This paper presents a machine learning method for detecting the mooring failures of SFT (submerged floating tunnel) based on DNN (deep neural network). The floater-mooring-coupled hydro-elastic time-domain numerical simulations are conducted under various random wave excitations and failure/intact scenarios. Then, the big-data is collected at various locations of numerical motion sensors along the SFT to be used for the present DNN algorithm. In the input layer, tunnel motion-sensor signals and wave conditions are inputted while the output layer provides the probabilities of 21 failure scenarios. In the optimization stage, the numbers of hidden layers, neurons of each layer, and epochs for reliable performance are selected. Several activation functions and optimizers are also tested for the present DNN model, and Sigmoid function and Adamax are respectively adopted to enhance the classification accuracy. Moreover, a systematic sensitivity test with respect to the numbers and arrangements of sensors is performed to find the appropriate sensor combination to achieve target prediction accuracy. The technique of confusion matrix is used to represent the accuracy of the DNN algorithms for various cases, and the classification accuracy as high as 98.1% is obtained with seven sensors. The results of this study demonstrate that the DNN model can effectively monitor the mooring failures of SFTs utilizing real-time sensor signals.

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“…Long et al [3] conducted parametric studies to investigate the effects of the BWR and mooring-line stiffness. Dynamic motions at varying BWRs and the corresponding comfort index were investigated by Long et al [20]. Seo et al [21] compared experimental results with simplified numerical approach for a segment of the SFT.…”

Section: Introductionmentioning

confidence: 99%

Time-Domain Hydro-Elastic Analysis of a SFT (Submerged Floating Tunnel) with Mooring Lines under Extreme Wave and Seismic Excitations

Jin

Kim

2018

Applied Sciences

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Global dynamic analysis of a 700-m-long SFT section considered in the South Sea of Korea is carried out for survival random wave and seismic excitations. To solve the tunnel-mooring coupled hydro-elastic responses, in-house time-domain-simulation computer program is developed. The hydro-elastic equation of motion for the tunnel and mooring is based on rod-theory-based finite element formulation with Galerkin method with fully coupled full matrix. The dummy-connection-mass method is devised to conveniently connect objects and mooring lines with linear and rotational springs. Hydrodynamic forces on a submerged floating tunnel (SFT) are evaluated by the modified Morison equation for a moving object so that the hydrodynamic forces by wave or seismic excitations can be computed at its instantaneous positions at every time step. In the case of seabed earthquake, both the dynamic effect transferred through mooring lines and the seawater-fluctuation-induced seaquake effect are considered. For validation purposes, the hydro-elastic analysis results by the developed numerical simulation code is compared with those by a commercial program, OrcaFlex, which shows excellent agreement between them. For the given design condition, extreme storm waves cause higher hydro-elastic responses and mooring tensions than those of the severe seismic case.

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Feasibility study on buoyancy–weight ratios of a submerged floating tunnel prototype subjected to hydrodynamic loads

Cited by 20 publications

References 22 publications

Coupled Vibration Analysis of Submerged Floating Tunnel System in Wave and Current

Coupled Vibration Analysis of Submerged Floating Tunnel System in Wave and Current

Mooring-Failure Monitoring of Submerged Floating Tunnel Using Deep Neural Network

Time-Domain Hydro-Elastic Analysis of a SFT (Submerged Floating Tunnel) with Mooring Lines under Extreme Wave and Seismic Excitations

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