Retrofitting of Floating Bridges With Perforated Outer Cover for Mitigating Wave-Induced Responses

2018 ◽  
Author(s):  
K. G. Vijay ◽  
T. Sahoo
Keyword(s):  
Structural Parameters ◽  
Domain Boundary ◽  
Wave Theory ◽  
Hydrodynamic Characteristics ◽  
Wave Forces ◽  
Vertical Force ◽  
Integer Multiple ◽  
Bridge Structures ◽  
Floating Bridges ◽  
Wave Induced

An investigation has been carried out based on multi-domain boundary element method to analyze the mitigation of wave-induced hydrodynamic loads on a pair of floating rectangular bridges by retrofitting the structures with external porous plates. The study is based on the assumptions of small amplitude water wave theory in finite water depth with the characteristics of wave-body interactions remain unaltered along the bridge. Wave past porous structure is modelled using Darcy’s law. Various hydrodynamic characteristics are studied by analyzing the wave forces acting on the floating bridges and the retrofitted porous structures for different wave and structural parameters. With the introduction of a retrofit, the horizontal force on the bridge reduces irrespective of wave and structural parameters, whilst vertical force increases under certain conditions. Moreover, when the distance between the bridges is an integer multiple of half of the wavelength of the incident waves, both the bridges experience optima in horizontal and vertical wave forces, with both these forces being 180° out of phase. The present study is expected to be useful in the design of efficient bridge structures which will reduce wave-induced hydrodynamics loads on the structure and thus enhance the service life of floating bridges.

scholarly journals WAVE FORCES ON PILES OF VARIABLE DIAMETER

1982 ◽  
Vol 1 (18) ◽  
pp. 108
Author(s):  
Bernard LeMehaute ◽  
James Walker ◽  
John Headland ◽  
John Wang
Keyword(s):  
Wave Field ◽  
Intertidal Zone ◽  
Wave Theory ◽  
Wave Force ◽  
Wave Forces ◽  
Linear Wave ◽  
Inertial Effects ◽  
Linear Wave Theory ◽  
Variable Diameter ◽  
Wave Induced

A method of calculating nonlinear wave induced forces and moments on piles of variable diameter is presented. The method is based on the Morrison equation and the linear wave theory with correction parameters to account for convective inertial effects in the wave field. These corrections are based on the stream function wave theory by Dean (1974). The method permits one to take into account the added wave force due to marine growth in the intertidal zone or due to a protective jacket, and can also be used to calculate forces on braces and an array of piles.

scholarly journals A Semi-Analytical Model for Studying Hydroelastic Behaviour of a Cylindrical Net Cage under Wave Action

2021 ◽  
Vol 9 (12) ◽  
pp. 1445
Author(s):  
Mingyuan Ma ◽  
Hong Zhang ◽  
Dong-Sheng Jeng ◽  
Chien Ming Wang
Keyword(s):  
Analytical Model ◽  
Least Squares Method ◽  
Structural Parameters ◽  
Free Water ◽  
Wave Theory ◽  
Porous Membrane ◽  
Wave Forces ◽  
Different Depths ◽  
Net Cage ◽  
Net Cages

In the present study, a semi-analytical model based on the small-amplitude wave theory is developed to describe the wave fields around a single gravity-type cylindrical open fish net cage. The cage may be submerged to different depths below the free-water surface. The fish cage net is modelled as a flexible porous membrane, and the deflection of the net chamber is expressed by the transverse vibration equation of strings. The velocity potential is expanded in the form of the Fourier–Bessel series and the unknown coefficients in these series are determined from matching the boundary conditions and the least squares method. The number of terms for the series solution to be used is determined from convergence studies. The model results exhibit significant hydroelastic characteristics of the net cages, including the distribution properties of wave surface, pressure drop at the net interface, structural deflection, and wave loading along the cage height. In addition, the relationships between wave forces on the net cage with hydrodynamic and structural parameters are also revealed. The findings presented herein should be useful to engineers who are designing fish cage systems.

scholarly journals Improvement on Structural Forms of Pile Group Foundations of Deepwater Bridges

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Enbo Yu ◽  
Sen Ren ◽  
Haojun Tang ◽  
Yongle Li ◽  
Chen Fang
Keyword(s):  
Slenderness Ratio ◽  
Wave Theory ◽  
Pile Group ◽  
Internal Force ◽  
Induced Response ◽  
Wave Forces ◽  
Long Span ◽  
The Stability ◽  
Wave Induced ◽  
Pile Length

As long-span cross-sea bridges extend to deeper sea areas, the bridge pile tends to increase in its slenderness ratio and becomes more susceptible to waves. To improve the structural stability at the construction stage, this study analyses wave-induced response of foundations. The wave theory and the method used for computing wave forces on foundations are first introduced. Then, a pile group foundation is taken as the research object, and different pile lengths ranging from 16 m to 46 m are considered. The wave-induced response of the piles and the cap is calculated. After understanding the effect of the pile length, three optimized foundations are proposed with the aim of reducing the free length of the pile, and the corresponding finite element models are established to compare their wave-induced response. The results show that the displacement at the top of the foundation increases with the increase in the pile length until the cap partly emerges from water and so does the internal force at the bottom. Setting a constraint in the middle of the piles can reduce their free lengths and is favourable to the wave-induced response of the foundation except for the shearing force. A stronger constraint shows better effects on improvement of the stability of the foundation. The conclusions provide reference for optimization on pile foundations of deepwater bridges.

Hydrodynamic coefficients of a floater near a partially reflecting seawall in the presence of an array of caisson blocks

2021 ◽  
pp. 1-23
Author(s):  
K G Vijay ◽  
Santanu Koley ◽  
Kshma Trivedi ◽  
Chandra Shekhar Nishad
Keyword(s):  
Wave Scattering ◽  
Structural Parameters ◽  
Wave Force ◽  
Vertical Force ◽  
Hydrodynamic Coefficients ◽  
Floating Structure ◽  
Surface Gravity Wave ◽  
Damping Coefficients ◽  
Half Wavelength ◽  
Scattering And Radiation

Abstract In the present study, surface gravity wave scattering and radiation by a freely floating rectangular buoy placed near a partially reflecting seawall and in the presence of an array of caisson blocks are analyzed. Various hydrodynamic parameters related to the wave scattering and radiation, such as the added mass and radiation damping coefficients, correspond to sway, heave and roll motions of the floating buoy, horizontal force, vertical force and moment acting on the floating structure, and horizontal wave force acting on the partially reflecting seawall are studied for a variety of wave and structural parameters. The study reveals that the resonating pattern in various hydrodynamic coefficients occurs for moderate values of the wavenumber. Further, when the distance between the floater and the sidewall is an integral time of half wavelength, the resonating behavior in the sway, heave and roll added masses, and associated damping coefficients appears, and the aforementioned hydrodynamic coefficients change rapidly around this zone. These resonance phenomena can be diminished significantly with appropriate positioning of the floater with respect to the sidewall and in the presence of partially reflecting seawall.

Effects of Cnoidal Wave-Induced Seepage on Vertical Breakwater Resting on Permeable Elastic Seabed

2014 ◽  
Vol 716-717 ◽  
pp. 284-288
Author(s):  
Jian Kang Yang ◽  
Hua Huang ◽  
Lin Guo ◽  
Jing Rong Lin ◽  
Qing Yong Zhu ◽  
...  
Keyword(s):  
Shallow Water ◽  
Wave Theory ◽  
Cnoidal Wave ◽  
Load Prediction ◽  
Wave Load ◽  
Seepage Pressure ◽  
Theoretical Investigations ◽  
Nonlinearity Effect ◽  
Wave Nonlinearity ◽  
Wave Induced

Theoretical investigations on cnoidal waves interacting with breakwater resting on permeable elastic seabed are presented in this paper. Based on the shallow water reflected wave theory and Biot consolidation theory on wave-induced seepage pressure, the analytical solutions to first order cnoidal wave reflection and wave-induced seepage pressure are obtained by the eigenfunction expansion approach. Numerical results are presented to show the effects of depth of water, breakwater geometry on cnoidal wave-induced seepage uplift force and overturning moment. Compared with Airy wave theory, in certain shallow water conditions, the shallow water wave theory can more effectively illustrate wave nonlinearity effect in wave load prediction.

Analytical investigation of nonlinear heave-coupled response of tension leg platform

2018 ◽  
Vol 233 (3) ◽  
pp. 699-713
Author(s):  
Mohammad Reza Tabeshpour ◽  
Reza Hedayatpour
Keyword(s):  
Degrees Of Freedom ◽  
Structural Response ◽  
Wave Theory ◽  
Equation Of Motion ◽  
Analytical Investigation ◽  
Response Analysis ◽  
Wave Forces ◽  
Tension Leg Platform ◽  
Heave Motion ◽  
Diffraction Effects

Having deep view in structural response of tension leg platform is important issue not only for response analysis but also for engineering design. Coupling between surge and heave motions of tension leg platform is such a problem. Here, tension leg platform motions are considered only in surge and heave degrees of freedom without pitch effect. The coupled term of heave is a nonlinear differential equation. Because the focus of this article is on this term, therefore, Duffing equation of motion in the surge direction is linearized. The wave forces are calculated using Airy’s wave theory and Morison’s equation, ignoring the diffraction effects. Current force also can be very important in dynamic analysis of tension leg platform. Because it affects the term of heave that is coupled with surge. It is shown that the effect of surge motion coupling on heave motion is very important in large displacement of surge motion in many sea states. The main result is that the coupling effects appeared in some frequencies such as heave and surge frequency, twice the frequency of wave, twice the natural surge frequency, and summation and difference of frequency of wave and surge frequency.

Experimental and numerical investigation of wave-current forces on coastal bridge superstructures with box girders

2019 ◽  
Vol 23 (7) ◽  
pp. 1438-1453 ◽  
Author(s):  
Jiawei Zhang ◽  
Bing Zhu ◽  
Azhen Kang ◽  
Ruitao Yin ◽  
Xin Li ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Numerical Models ◽  
Wave Forces ◽  
Vertical Force ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Coastal Bridges ◽  
Girder Bridges ◽  
Wave Parameters ◽  
Waves And Currents

Coastal bridges are exposed to hurricane waves and storm surges during hurricanes, which threaten the safety of the superstructures. Since waves and ocean currents coexist in the natural marine environment and the action of currents leads to changes in wave parameters and thus affects wave loads, considering their interaction is necessary for the study of wave forces on coastal bridges. In this study, hydrodynamic loads on a box girder with the joint action of regular waves and currents are investigated with both experiments and numerical models. A series of experiments of wave forces that include conditions with different wave heights, current velocities, wave periods and submergence depths are conducted in a wave flume. Two-dimensional numerical simulations are performed to further investigate the mechanics of wave-current forces on box girder bridges. The wave parameters and wave forces of the numerical simulations are compared with the experimental results. The results indicate that a following current usually leads to higher maximum horizontal forces and lower maximum vertical forces. The opposing current results in a higher maximum hydrodynamic vertical force than following current with a low submergence depth. However, due to the joint effect of the wave parameters and structure position relationships, the behaviours of wave forces in other situations become complicated. It is anticipated that this study can provide experimental data of wave-current forces for the superstructures of box girder bridges and enhance the understanding of the mechanism of bridge damage by waves and currents.

Subgrid-scale structure and fluxes of turbulence underneath a surface wave

2019 ◽  
Vol 878 ◽  
pp. 768-795
Author(s):  
Kuanyu Chen ◽  
Minping Wan ◽  
Lian-Ping Wang ◽  
Shiyi Chen
Keyword(s):  
Strain Rate ◽  
Eddy Viscosity ◽  
Isotropic Turbulence ◽  
Wave Theory ◽  
Viscosity Model ◽  
Strain Rate Tensor ◽  
Linear Wave ◽  
Subgrid Scale ◽  
Eddy Viscosity Model ◽  
Wave Induced

In this study, the behaviours of subgrid-scale (SGS) turbulence are investigated with direct numerical simulations when an isotropic turbulence is brought to interact with imposed rapid waves. A partition of the velocity field is used to decompose the SGS stress into three parts, namely, the turbulent part $\unicode[STIX]{x1D749}^{T}$, the wave-induced part $\unicode[STIX]{x1D749}^{W}$ and the cross-interaction part $\unicode[STIX]{x1D749}^{C}$. Under strong wave straining, $\unicode[STIX]{x1D749}^{T}$ is found to follow the Kolmogorov scaling $\unicode[STIX]{x1D6E5}_{c}^{2/3}$, where $\unicode[STIX]{x1D6E5}_{c}$ is the filter width. Based on the linear Airy wave theory, $\unicode[STIX]{x1D749}^{W}$ and the filtered strain-rate tensor due to the wave motion, $\tilde{\unicode[STIX]{x1D64E}}^{W}$, are found to have different phases, posing a difficulty in applying the usual eddy-viscosity model. On the other hand, $\unicode[STIX]{x1D749}^{T}$ and the filtered strain-rate tensor due to the turbulent motion, $\tilde{\unicode[STIX]{x1D64E}}^{T}$, are only weakly wave-phase-dependent and could be well related by an eddy-viscosity model. The linear wave theory is also used to describe the vertical distributions of SGS statistics driven by the wave-induced motion. The predictions are in good agreement with the direct numerical simulation results. The budget equation for the turbulent SGS kinetic energy shows that the transport terms related to turbulence are important near the free surface and they compensate the imbalance between the energy flux and the SGS energy dissipation.

Hydrodynamic Characteristics of ROVs During Deployment Through Wave-Affected Zones

2015 ◽  
Author(s):  
Musa B. Bashir ◽  
Mahesh Menon ◽  
Simon D. Benson ◽  
Rob Eastwood ◽  
Alan J. Murphy ◽  
...  
Keyword(s):  
Potential Theory ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Splash Zone ◽  
Load Prediction ◽  
Hydrodynamic Analysis ◽  
Motion Response ◽  
Recovery System ◽  
Maximum Range ◽  
Wave Induced

The prediction of wave-induced loads on Remotely Operated Vehicles (ROVs) during deployment through the splash zone is an important requirement to the design of a launch and recovery system. This paper presents the results of numerical and experimental hydrodynamic analysis of the motion response and wave-induced loads on a subsea trencher ROV during its deployment through the splash zone. The main focus of the study is to determine the maximum wave-induced loads and also to establish the maximum range of sea conditions in which the ROV can be operated safely. The numerical measurement of the hydrodynamic responses is completed using a 3D potential theory–based solver. The results obtained are compared with the predicted experimental responses measured using a 1/12 scale model of the ROV in a wave tank. A further comparison of the numerical responses with a box-shaped model of approximately similar overall dimensions to the ROV is performed in order to establish the validity of using a simplified shape to represent the actual ROV in various modelling scenarios. The result of this comparison shows that using a box-shaped model grossly over-predicts the responses and can lead to overly conservative load prediction.

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