Theoretical Study on Hydroelastic Responses of Very Large Floating Structures Near Islands and Reefs

2014 ◽  
Author(s):  
Chao Tian ◽  
Xinyun Ni ◽  
Jun Ding ◽  
Peng Yang ◽  
Yousheng Wu
Keyword(s):  
Large Scale ◽  
Oil And Gas ◽  
Linear Equations ◽  
Dynamic Responses ◽  
Wave Loads ◽  
Structural Dynamic ◽  
Floating Structures ◽  
Geological Conditions ◽  
Incident Waves ◽  
Very Large Floating Structures

In order to explore the fishery, oil and gas, and tourism resources in the ocean, Very Large Floating Structures (VLFS) can be deployed near islands and reefs as a logistic base with various functions such as a floating harbor, accommodation, fishery processing, oil and gas exploration, environment surveillance, airplane landing and taking off, etc. However, in addition to the complicated hydroelastic coupling effects between the hydrodynamic loads and structural dynamic responses, when tackling the hydroelastic problems of floating structures deployed near islands and reefs, several other environmental effects and numerical techniques should be taken into account: 1) The influences of the non-uniform incident waves (multi-directions, different wave frequencies); 2) Complex seabed profile and its impact on the incident waves; 3) Nonlinear second order wave exciting forces in the complex mooring system, shallow water and coral reef geological conditions; 4) Parallel computing technology and fast solving methods for the large scale linear equations, accounting for the influence of dramatic increase of number of meshes to the computation efforts and efficiency. In the present paper the theoretical investigation on the hydroelastic responses of VLFS deployed near islands and reefs has been presented. In addition, based on the pulsating source Green function, the high performance parallel fast computing techniques and other numerical methods, in solving large scale linear equations, have been introduced in the three-dimensional hydroelastic analysis package THAFTS. The motions, wave loads, distortions and stresses can be calculated using the present theoretical model and the results can be used in the design and safety assessment of VLFS.

Concept Design of Very Large Floating Structures and Laboratory-Scale Physical Modelling

2019 ◽  
Author(s):  
Lorenzo Cappietti ◽  
Irene Simonetti ◽  
Ilaria Crema
Keyword(s):  
Numerical Models ◽  
Physical Modelling ◽  
Building Blocks ◽  
Small Scale ◽  
World Population ◽  
Concept Design ◽  
Wave Loads ◽  
Experimental Database ◽  
Floating Structures ◽  
Very Large Floating Structures

Abstract The use of Very Large Floating Structures, VLFS, may represent a strategic approach in order to cope with some of the future societal challenges arising from the impressive growth of the world population. In this article, the motivations of this perspective are briefly discussed, the main issues for the development of VLFS are summarized and a concept structural design based on building-blocks technology is proposed. A small-scale physical model was manufactured and tested in the wave-current flume of the Laboratory of Maritime Engineering, LABIMA, of the Florence University, Italy. The aim of this study is the assessment of the structural feasibility and the effectiveness of the proposed VLFS concept, in terms of resistance to wave loads and control of floating behavior. The experimental measurements provide a first contribution to the necessary knowledge, about load magnitudes and floating behavior, for sizing some of the key structural components. The results appear to support the feasibility of the system in terms of usage of structural materials, technical components and building technologies, available at present, that can withstand the measured loads. Moreover, the acquired experimental database is fundamental in order to validate numerical models, in the perspective of using also such tools as complementary methodology for further improvement of the knowledge of design issues.

scholarly journals Seismic Analysis of 10-MW Off Shore Wind Turbine with Large-Diameter Monopile in Consideration of Seabed Liquefaction

2021 ◽  
Author(s):  
Jian Zhang ◽  
Songye Zhu ◽  
Guo-Kai Yuan ◽  
Quan Gu ◽  
Shitang Ke ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Large Scale ◽  
Seismic Analysis ◽  
Large Diameter ◽  
Soil Liquefaction ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Wind Loading ◽  
Geological Conditions ◽  
The Impact

Abstract With the increasing construction of large-scale wind turbines in seismically active coastal areas, the survivability of these high-rated power offshore wind turbines (OWTs) in marine and geological conditions becomes extremely important. Although research on the dynamic behaviors of OWTs under earthquakes has been conducted in consideration of soil-structure interaction, attention paid to the impact of earthquake-induced seabed liquefaction on OWTs supported by large-diameter monopiles is limited. In view of this research gap, this study carries out dynamic analyses of a 10-MW OWT under the combined wind, wave, and earthquake loadings. This study uses a pressure-dependent multi-surface elastoplastic constitutive model to simulate the soil liquefaction phenomenon. Results indicate that the motion of the large-diameter monopile leads to more extensive soil liquefaction surrounding the monopile, specifically in the zone near the pile toe. Moreover, compared with earthquake loading alone, liquefaction becomes more severe under the coupled wind and earthquake loadings. Accordingly, the dynamic responses of the OWT are apparently amplified, demonstrating the importance of considering the coupling loadings. Compared with wind loading, the effect of wave loading on the dynamic response and liquefaction potential is relatively insignificant.

scholarly journals Experimental Evidence of the Influence of Recurves on Wave Loads at Vertical Seawalls

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 889 ◽  
Author(s):  
Dimitris Stagonas ◽  
Rajendran Ravindar ◽  
Venkatachalam Sriram ◽  
Stefan Schimmels
Keyword(s):  
Large Scale ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Wave Loads ◽  
Incoming Wave ◽  
Wave Heights ◽  
The Mean ◽  
Peak Pressures ◽  
Wave Induced ◽  
Incident Waves

The role of recurves on top of seawalls in reducing overtopping has been previously shown but their influence in the distribution and magnitude of wave-induced pressures and forces on the seawall remains largely unexplored. This paper deals with the effects of different recurve geometries on the loads acting on the vertical wall. Three geometries with different arc lengths, or extremity angles (αe), were investigated in large-scale physical model tests with regular waves, resulting in a range of pulsating (non-breaking waves) to impulsive (breaking waves) conditions at the structure. As the waves hit the seawall, the up-rushing flow is deflected seawards by the recurve and eventually, re-enters the underlying water column and interacts with the next incoming wave. The re-entering water mass is, intuitively, expected to alter the incident waves but it was found that the recurve shape does not affect wave heights significantly. For purely pulsating conditions, the influence of αe on peak pressures and forces was also negligible. In marked contrast, the mean of the maximum impulsive pressure and force peaks increased, even by a factor of more than two, with the extremity angle. While there is no clear relation between the shape of the recurve and the mean peak pressures and forces, interestingly the mean of the 10% highest forces increases gradually with αe and this effect becomes more pronounced with increasing impact intensity.

The Effect of Current on the Dynamic Responses of Truss Spar in Malaysia Water

2016 ◽  
Author(s):  
S. N. A. Tuhaijan ◽  
C. Y. Ng ◽  
V. J. Kurian
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Model Tests ◽  
Dynamic Responses ◽  
Water Current ◽  
Sea Waves ◽  
Structural Dynamic ◽  
Gas Industry ◽  
Truss Spar

In South East Asia, Malaysia is one of the leading countries in the oil and gas industry. Today, Malaysia has expanded the explorations into the deeper water region. Before the installation of the Malaysia first deepwater platform, the Kikeh Spar, spar platforms can only be found in the Gulf of Mexico. Malaysian offshore regions are subjected to significant water current. From the literature review carried out, it was found that the current would change the behavior of the sea waves. This is contributing significantly to the environmental loading and affect the dynamic responses of the offshore structures. Hence, the study that focused on the effects of the current together with the wave on the structural dynamic response is necessary. In this study, the effect of the current coexisting with the wave on the dynamic responses of a truss spar model was experimentally investigated and quantified. The model tests were performed in the wave tank of the Offshore Laboratory in Universiti Teknologi PETRONAS with a scaling factor of 1:100. Two sets of environmental conditions were considered in the model tests i.e. wave only and wave-current condition. The dynamic responses of the truss spar model subjected to these conditions were measured. In order to quantify the effect of current, the measured results for the condition with and without current were compared among and presented here. From this investigation, it was found that the existence of the current in the water body has increased the truss spar motions, whereby the higher current velocity, give the higher response.

Wind self-excited force models suited for floating bridges

2021 ◽  
Author(s):  
Mitja Papinutti ◽  
Ole Øiseth ◽  
Ketil Aas-Jakobsen
Keyword(s):  
Wind Tunnel Test ◽  
Dynamic Responses ◽  
Wave Radiation ◽  
Viscous Drag ◽  
Wave Loads ◽  
Floating Structures ◽  
Aerodynamic Damping ◽  
Long Span ◽  
Hydrodynamic Damping ◽  
Floating Bridge

<p>The conceptual design of any floating bridge requires detailed investigations of its dynamic responses to achieve safe and reliable structures. Floating structures are subject to dynamic excitations due to wind or wave loads. Low structural damping is expected for long-span floating structures, and additional environmental damping is therefore much appreciated. The most important dynamic loads are wave and wind loads, where wave radiation damping, viscous drag damping, and aerodynamic damping strongly influences the overall response. Compared to hydrodynamic damping, aerodynamic damping covers a broader frequency range, stretching over multiple eigenmodes. Therefore, aerodynamic damping represents an important contribution and is the main topic of this publication. A short overview of available self-excited load models is presented. Different models are tested numerically and compared to the wind tunnel test.</p>

A study on reliability-based design systems of very large floating structures under extreme wave loads

2001 ◽  
Vol 14 (1-2) ◽  
pp. 259-272 ◽  
Author(s):  
Alejandro L. Talavera ◽  
Koji Masaoka ◽  
Takashi Tsubogo ◽  
Hiroo Okada ◽  
Yoshisada Murotsu
Keyword(s):  
Wave Loads ◽  
Extreme Wave ◽  
Floating Structures ◽  
Reliability Based Design ◽  
Design Systems ◽  
Very Large Floating Structures
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