The Stability of Offshore Structures

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Ocean Engineering".

Deadline for manuscript submissions: closed (25 October 2023) | Viewed by 5785

Special Issue Editor

Department of Civil and Environmental Engineering, University of Surrey, Guildford GU2 7XH, UK
Interests: development of DEM platform for granular materials; foundation stability for offshore wind farms; sustainable energy, including offshore wind energy, geothermal energy, and methane hydrate exploitation

Special Issue Information

Dear Colleagues,

Offshore structures are essential platforms constructed by the energy sector for traditional oil and gas exploitation and renewable offshore energy harvesting. Their forms are complex and vary significantly with water depth and the purpose of applications. These structures are subjected to complex environmental loadings from wind, waves, and currents in normal operational conditions, but also from typhoons, tsunamis, marine landslides, or earthquakes in extreme conditions. Therefore,  the long-term stability of offshore structures under complex environmental loadings is a vital issue to guarantee serviceability throughout their designed life. This special issue will focus on the developments and advancements in this field covering, but not limited to, new analysis and modelling methodology, prediction of long-term responses under dynamic loadings, novel designs of offshore structures, and solutions to address long-term instabilities.

Dr. Liang Cui
Guest Editor

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Keywords

  • offshore structure
  • offshore renewable energy
  • dynamic responses
  • characterising wind, wave, and current loads
  • numerical modelling
  • physical modelling

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Published Papers (3 papers)

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Research

23 pages, 5839 KiB  
Article
Numerical Analysis of Dynamic Response and Liquefaction Phenomena in Sandy Seabed Foundation around a Semi-Circular Breakwater under Wave Loading
by Junwei Liu, Yunping Jia, Lin Cui, Honglei Sun, Xu Lv and Mohsen Saleh Asheghabadi
J. Mar. Sci. Eng. 2024, 12(1), 40; https://doi.org/10.3390/jmse12010040 - 23 Dec 2023
Cited by 1 | Viewed by 1138
Abstract
Understanding the stability of the seabed foundation holds paramount significance in guaranteeing the safety and structural soundness of the breakwater alongside additional offshore structures. This study aimed to investigate the stability of a sandy seabed foundation around a semi-circular breakwater under wave loading [...] Read more.
Understanding the stability of the seabed foundation holds paramount significance in guaranteeing the safety and structural soundness of the breakwater alongside additional offshore structures. This study aimed to investigate the stability of a sandy seabed foundation around a semi-circular breakwater under wave loading in nearshore areas. A coupled numerical model of waves, a semi-circular breakwater, and the seabed was developed based on the OpenFOAM platform. The VARANS equations were used to govern the wave behavior. Meanwhile, the Biot’s partially dynamic model was employed to numerically simulate the seabed response considering both consolidation under self-weight and dynamic response under wave loading. The effects of various wave parameters, seabed properties, and the radius of the structure on the dynamic response of the seabed and the depth of liquefaction were investigated. The numerical results indicate that an increase in wave height, period, and permeability coefficient intensifies the dynamic response of the seabed soil. Furthermore, an increase in water depth weakened the soil’s dynamic response. There was a negative correlation between the radius of the semi-circular breakwater and the dynamic response. The influence of Poisson’s ratio on the dynamic response of the seabed was relatively small. Furthermore, a stronger dynamic pore pressure response was observed at the connection between the semi-circular breakwater and the rubble foundation. Full article
(This article belongs to the Special Issue The Stability of Offshore Structures)
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22 pages, 15349 KiB  
Article
Structural Analysis Procedure and Applicability Review of Spudcan Considering Soil Types
by Joo-Shin Park, Dong-Hun Lee and Myung-Su Yi
J. Mar. Sci. Eng. 2023, 11(9), 1833; https://doi.org/10.3390/jmse11091833 - 20 Sep 2023
Cited by 2 | Viewed by 1695
Abstract
As interest in eco-friendly energy development continues to rise, the offshore wind turbine market is growing at a high rate of increase every year. In line with this, the demand for installation vessels with large capacity is also increasing rapidly. WTIVs (Wind Turbine [...] Read more.
As interest in eco-friendly energy development continues to rise, the offshore wind turbine market is growing at a high rate of increase every year. In line with this, the demand for installation vessels with large capacity is also increasing rapidly. WTIVs (Wind Turbine Installation Vessels) employ spudcans in the seabed for the installation of wind turbines. Currently, the assessment of spudcans is an important issue in ensuring structural safety in the entire structure system. This study examines the current procedure suggested by classification societies and a new procedure that accounts for the new loading scenarios based on realistic operating conditions. This new procedure is further validated through an FEA (Finite Element Analysis). The current procedure yields maximum stress values below the allowable criteria because it does not consider the effect of the seabed slope, the leg bending moment, and the spudcan shape. However, the results of some load conditions as defined in the new procedure confirm the need for reinforcement under actual preload conditions. Therefore, the new procedure considers a broader range of real-world operating conditions, and the possible problems were verified through a detailed FEA. Full article
(This article belongs to the Special Issue The Stability of Offshore Structures)
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18 pages, 8092 KiB  
Article
Soil–Structure Interactions for the Stability of Offshore Wind Foundations under Varying Weather Conditions
by Liang Cui, Muhammad Aleem, Shivashankar and Subhamoy Bhattacharya
J. Mar. Sci. Eng. 2023, 11(6), 1222; https://doi.org/10.3390/jmse11061222 - 14 Jun 2023
Cited by 4 | Viewed by 1562
Abstract
Fixed-bottom foundations of offshore structures, mainly monopiles, are subject to extreme events and other critical cyclic nature loads. Since offshore wind turbine structures are slender, the manufacturers of offshore wind turbines give a range of frequencies for safe operation during a structure’s life [...] Read more.
Fixed-bottom foundations of offshore structures, mainly monopiles, are subject to extreme events and other critical cyclic nature loads. Since offshore wind turbine structures are slender, the manufacturers of offshore wind turbines give a range of frequencies for safe operation during a structure’s life cycle. Highly reliable measurements and accurate determination of shear moduli and damping ratios are crucial to ensure the stability of these structures, for example, to avoid the resonance of the structures. Because foundation–soil properties change over a period of time due to various environmental factors, this should be taken into consideration for designs. In the current investigation, behaviours of dry sand under dynamic loads were explored. Cyclic loads of strain amplitudes of 0.05%, 0.1%, 0.25% and 0.5% were carried out in a cyclic simple shear apparatus to explore the evolution trend of the stiffness and damping ratio of the soil. Attempts were made to simulate varying weather conditions by conducting cyclic tests with different strain amplitudes representing normal weather conditions and extreme weather conditions. It was found that soil dynamic properties vary remarkably at first and then tend to stabilise under cyclic loading with the same strain amplitude. However, with varying strain amplitude, property variations continue further. From numerical analyses using the discrete element method, it was found that this is due to the disturbance of soil, causing further particle rearrangements and soil compactions, following a sudden change of strain amplitude, which leads to further property variations. Full article
(This article belongs to the Special Issue The Stability of Offshore Structures)
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