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The installation of offshore structures and facilities in the marine environment, usually for the production and transmission of oil, gas exploration, electricity, and other natural resources is referred to as offshore construction. Since offshore structures are subjected to changing threats to the environment year-round. Fatigue behavior prediction noticed on these structures should be considered during the design stage. Fatigue is one of the failure mechanisms of offshore steel structures, and it must be investigated properly during system design. The fatigue analysis of offshore structures under drag wave force, total wave force, total moment about the sea bed, and other variables are reviewed thoroughly. The structure's dynamic response becomes a critical aspect in the whole design process. The fatigue analysis was carried out using MATLAB software, material properties of the offshore structure, and wave spectrum characteristics in this study. This study shows the JONSWAP spectrum and stress concentration analysis prediction. The offshore support structure that is predicted during the design phase will help to keep the stress concentration factor below the fatigue threshold and anticipate safe life design, according to the results of the fatigue study. The fatigue performances of tripod and jacket steel support structures in intermediate waters depth are compared in this project (20-50 m). The North Atlantic Ocean is used as a reference site, with a sea depth of 45 meters. The tripod and jacket support structures will be designed by using current industry standards. Keywords: [Fatigue evaluation, North Atlantic Ocean and Failure].

The implementation of economic projects in the Arctic zone requires a rational and environmentally-balanced approach within the framework of the sustainable nature management model. In order to minimize the negative consequences for the environment, it is customary to consider options and compare alternative design solutions that determine the impact indicators and ways to manage the environmental aspects of economic activity.Based on the results of field studies conducted in the Sharapov Shar Gulfin the Kara Sea,the characteristic features of the ice situation were identified, which are not covered in the current regulatory documents, but are necessary for the development of design documentation for hydraulic structures in compliance with the principles of sustainable development. Ice loads on a hydraulic structure should be determined on the basis of the ice situation in the structure construction area for the time period with the greatest ice impacts. The method for determining ice loads taking into account the features of stable fast ice is presented. The comparative analysis of hydraulic structures for construction in Sharapov Shar Gulf has been performed, the Gulf is a rare example of an area where sea ice forms stable ice fast ice throughout the entire period of maximum ice strength,which makes it possible to optimize design solutions. An analysis of the adequacy of the current RF regulatory requirements for performing engineering surveys and calculating the ice load was carried out, followed by the comparative analysis of the calculation results. The possibility of designing a gravity offshore hydraulic structure in the conditions of the Sharapov Shar Gulf has been substantiated, which significantly reduces the impact on the environment in comparison with alternative options suitable for the conditions of the Gulf. The PLAXIS2D software package is used to perform numerical simulation of the stress-strain state of the “ice-structure-base” system for the maximum load for each of the phases of the ice period, taking into account the nonlinear properties of the base soils. The development strategy of the project of a gravity hydraulic structure in the shallow waters of the Arctic sea shelf is determined using the elements of SWOT analysis. The gravity design of a hydraulic structure has obvious environmental advantages, which are expressed in minimal impact indicators in relation to other design options.

Sustainability is the ability of the system to retain and survive its functionality with time. A system is sustainable as long as the capacity (supply) is greater than the load (demand). Along the timeline of the project, the options to ensure sustainability minimize inferring better planning considerations at early stages. Geotechnical engineering, being the opening phase of any construction project, can contribute most to attain sustainability goals for all aspects, i.e. engineering, environmental, economic, and equity (4Es). Through a survey and available literature, it has been concluded that geotechnical engineering lacks a dedicated sustainability assessment tool/technique. Different assessment techniques/tools and technical aspects of geotechnics were studied to develop Geo-SAT (Geotechnical Sustainability Assessment Tool). Geo-SAT is developed to ensure the lack of research encompassing global sustainability goals. Based on quantifiable indicators assessed by a third party on a scale of 1 (detrimental) to 5 (significantly improved) measuring the impact on sustainability for each decision made, a total of 171 indicators were developed (all generic in nature) with the flexibility of addition, exclusion, and/or modification as per project’s nature. The engineering aspect is developed using 92 indicators, 27 retained and 8 modified from Environmental Geotechnics Indicators (EGIs), and 57 new. The different fields targeted are dams, foundations, landslides, contaminated site remediation, soil and erosion control, offshore construction, and transportation.

The American Society of Civil Engineers set three pillars of sustainability, the triple bottom line approach, revolving around the environment, economy and equity. This approach is aligned with the Sustainable Development Goals set by the United Nations. Activities undertaken in any construction project must follow this approach and must be audited to validate their impact on sustainability. Geotechnical projects lack an audit/assessment tool encompassing the triple bottom line. Efforts were made to modify SPeAR (Sustainable Project Appraisal Routine) into Geotechnical SPeAR, but the system lacks the quantification scale as used by Environmental Geotechnics Indicators. The study aims to develop a new tool called Geo-SAT (Geotechnical Sustainability Assessment Tool), overcoming these limitations, incorporating engineering as a vital pillar. Geo-SAT is based on indicators quantified on a scale of 1 (detrimental) to 5 (significantly improved) to assess the impact of actions taken or considered, on sustainability. The total number of indicators developed is 169 out of which 79 are specific to the triple bottom line approach and 90 to engineering. These indicators are generic and can be used for geotechnical projects with the flexibility of exclusion as per the nature of the project. The different fields targeted are dams, foundations, landslides, contaminated site remediation, soil and erosion control, offshore construction and transportation. This tool will serve as a potential code of sustainability for geotechnical projects.

As part of the Monaco offshore urban extension project, Bouygues TP is in charge of design & build a maritime infrastructure as the first step of the six-hectare expansion of the city into the sea. This maritime infrastructure consists of a fill enclosed by a band of trapezoid concrete caissons and will serve as base for construction of the new residential area. The paper focuses on some of the problems which had to be solved: optimization of promenade level and wave absorbing chambers in conjunction with minimal reflection and safety related to overtopping, accounting for sea level rise and correlation between extreme waves and water levels. caissons and rubble mound foundation stability related to waves and seism, including extra seismic forces due to buildings considering the high reclamation height and the immediate proximity of building foundations. the way in which caissons representing nearly 80,000 m3 of concrete can be built in a floating and continuous manner via a caisson box (or "caissonnier" in French), within a particularly short time frame presence of a small craft harbor with shops along the quays, whose location was fixed for urbanistic reasons, which requested optimizations in detail of anti-overtopping devices as much as possible integrated in the urban context, need to convert a breakwater caisson into a low crested swimming pool caisson, with plexiglas windows exposed to wave slamming from outside, but also from inside due to overtopping impacts over the swimming pool basin. Ecodesign has been closely associated with hydrodynamic and coastal engineering, based on estimation of wave pressures and induced velocities in the different possible locations (chambers, walls, structures toes …). The eco-friendly development strategy is based on the wide-scale deployment of a range of 11 solutions which will be described (potential for caissons to be colonized, nursery function development, etc…). Moreover, posidonia transplantation has been done via concrete open boxes, whose stability under storm waves has requested CFD calculations to model local velocities and optimize their shape.

The misalignment of wind and waves is of special interest for various engineering applications, i.e. for structural fatigue load analyses, for work vessel operations for offshore construction or maintenance, and for floating wind turbines. In addition to the normal or frequent boundary conditions, the combination of extreme loads and their directions is essential for coastal and offshore designs. These aspects are addressed by analyzing ten years of field measurements in the German Bight of the North Sea, which is intensively used for offshore wind energy production. This paper focuses on the occurrence and amount of wind and wave misalignment as well as the direction dependency of the wind-wave correlation for normal conditions and extreme storms. Subsequently, the influence of statistical distribution functions for the estimation of extreme wind and wave values is presented. Based on these results, a method is developed to combine direction dependent extreme wind and wave incidents for return periods of several decades.

Position control for heavy-lift construction vessels is crucial for safe operation during offshore construction. During the various phases of a typical offshore construction assignment, considerable changes in the dynamics of the crane-vessel system occur. Operational hazard was reported if such interchanging dynamics are not properly handled. However, to date and the best of our knowledge, no systematic control solution is reported considering multiphase offshore construction scenarios. This article proposes a switched dynamical framework to model the interchanging phases and to formulate a comprehensive position control solution for heavy-lift vessels. Stability and robustness against modeling imperfections and environmental disturbances are analytically assessed. The effectiveness of the solution is verified on a realistic heavy-lift vessel simulation platform; it is shown that the proposed switched framework sensibly improves accuracy and reduces hazard compared with a nonswitched solution designed for only one phase of the construction scenario.

Summary Shallow permafrost is associated with significant potential risks for offshore construction and drilling as well as ecological risks that may occur when the permafrost is disturbed due to the human activities. Identification and mapping of the shallow permafrost areas is one of the major tasks of the site survey investigations in the Russian Arctic. Due to the lack of engineering drilling data on the Arctic shelf, remote geological and geophysical studies, such as multichannel high, very-high and ultra-high resolution (HR, VHR and UHR) seismic surveys, are increasingly being used to map and characterize the subaquatic permafrost. In the paper, we present an approach to 3D VHR reflection seismic data interpretation that allowed us to the built a volumetric model of the shallow permafrost and assess its acoustic properties in the shelf of the Kara sea. To our knowledge, this is the first ever demonstrated detailed 3D model of the shallow permafrost in the Russian Artic.

Offshore Service Vessels (OSV) are utilized for demanding offshore operations often under challenging conditions, e.g. Anchor Handling Tug Supply vessel (AHTS) supporting offshore drilling rigs and Offshore Construction Vessels performing subsea installation. The OSV case in the HOLISHIP project has addressed both these vessel concepts with the main focus on power system optimization based on the operational profile for the vessel. Regarded as highly specialized vessels, OSV design requires the synchronization of several of disciplines. Thus, a holistic approach, considering Key Performance Indices (KPIs) for several disciplines, was developed and utilized from a conceptual design level to the power system concept verification. Sub-optimization of each module for different KPIs without taking into account the interaction between the modules does not necessarily lead to an optimized overall performance of the vessel and a holistic approach design is highly likely to be beneficial. At the early design stage of a vessel, important parameters are defined having a huge impact on the performance of the vessel according to the KPIs. Changing these parameters at a later stage in the design process is difficult and requires a considerable effort from the multidisciplinary design team. This Chapter presents the holistic design of the OSV application case from main dimension determination to power system design, optimization and verification. Significant improvements for selected KPIs have been obtained comparing the optimized concept with the baseline vessel. The design optimization methods developed here are already being used in other research and commercial projects proving increase efficiency in the early design stage. The methods for virtual verification using dynamic simulations are being further developed and used in other research projects.

How to extract useful and key information from the original big wave data with large volume and low information density and establish a wave climate datasets is still in a blank status, which is also urgently needed in the ocean navigation, deep sea development, marine resource development, offshore construction, and disaster prevention and mitigation, etc. Based on the ERA-interim wave data for 1979–2018 and ERA-40 wave reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF), this study adopts the climate statistical analysis methods to establish the first open and public wave climate dataset for the Maritime Silk Road, systematically including the prevailing wave direction and significant wave height (SWH), wave period, swell index (SI), rough sea occurrence, wave direction occurrence, co-occurrence of wave height and wave direction, co-occurrence of wave height and wave period, and extreme wave height. It is hoped that the results can provide a data support for the safe and efficient deployment of marine development and construction.

This paper introduces a promising topology of remote offshore wind farms sending through multi-terminal VSC-HVdc link, considering the special offshore construction and operation conditions, and referring to some multi-terminal VSC-HVdc projects already in operation in China. Based on this topology, the control strategy is designed and start-up process is introduced. In the end, three terminals' case including two offshore terminals is simulated in PSCAD/EMTDC platform. Different operation modes are discussed in the simulation, and the simulation results show that this multi-terminal VSC-HVdc system shows good performance in steady and transient states and can be a good choice for the power transmission of remote adjacent wind farms.

Material Management Plan is an integrated supply chain management (SCM) process that is synchronized to the project management plan (PMP) to ensure that the project materials are all available when the point of time it is needed. Material Management Plan has a vital role in managing project management, especially in the offshore construction industry. It also plays a major role because of the success of every construction project relies heavily on having material available on time at a reasonable cost. Despite the importance of the Material Management Plan for the construction of offshore projects, the contractors are still experiencing loss of productivity, project delays, and cost overrun due to the absence of proper execution of material management plan. The main aim of this research is two-fold. First, is to explore the current material management practice and its impact on delivering the offshore fixed platforms Project. Second, to identify the root cost of ineffective material management by utilizing Six Sigma and Failure Mode and Effect Analysis (FMEA). In conclusion, exploring the critical process of material management plan towards project performance will benefit the offshore construction player in improving the efficiency of material management. This will help to minimize the (bad) impact on construction project performance.

This paper presents an overview of quality control issues of submarine cables in project cycle of offshore wind power projects in Jiangsu. After analyzing all stages of the overall process of an offshore wind power project cycle, different focus quality control issues related to submarine cable, such as design flaw, reinstallation, harsh offshore construction conditions, damage by external force, application of land cable accessories, excessive ground current and uneven distribution between layers are listed in detail following accident cases. In the end, several practical advices and methods such as the preferences of three-core submarine cable and dry pluggable terminal, improvement of standards of quality control test methods and life cycle management measures are given, in order to improve the quality control of submarine cables.

Tidal and wind-driven near-inertial currents play a vital role in the changing Arctic climate and the marine ecosystems. We compiled 429 available moored current observations taken over the last two decades throughout the Arctic to assemble a pan-Arctic atlas of tidal band currents. The atlas contains different tidal current products designed for the analysis of tidal parameters from monthly to inter-annual time scales. On shorter time scales, wind-driven inertial currents cannot be analytically separated from semidiurnal tidal constituents. Thus, we include 10–30 h band-pass filtered currents, which include all semidiurnal and diurnal tidal constituents as well as wind-driven inertial currents for the analysis of high-frequency variability of ocean dynamics. This allows for a wide range of possible uses, including local case studies of baroclinic tidal currents, assessment of long-term trends in tidal band kinetic energy and Arctic-wide validation of ocean circulation models. This atlas may also be a valuable tool for resource management and industrial applications such as fisheries, navigation and offshore construction., Measurement(s) ocean current Technology Type(s) Gauge or Meter Device • digital curation Factor Type(s) time • current • geographic location • tidal current Sample Characteristic - Environment ocean Sample Characteristic - Location Arctic Ocean region Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12581435

The shipbuilding industry and marine economic services can be considered as one of the potential industries, a spearhead and an important motive of the marine economy in coastal countries. For serving the marine economy and being able to exploit marine resources, an enormous industry has been developed, using floating rigs, boats and fixed production platforms or anchoring on the sea. These floating structures require different types of support activities and to provide the necessary assistance, many different types of ships have been produced. The common function of offshore construction serving vessels are to support the fields of energy exploitation, continental shelf exploitation, oil and gas exploitation, geological survey and some other offshore industrials and services. Each type of ship can be designed to perform a single specific task, but in usal, each type of ship is designed to perform a combination of tasks. When integrating multiple tasks in one type of vessel, the designer must come up with the most suitable plan to satisfy the conflicting requirements, and must meet the operational requirements and the corresponding safety codes. This paper focuses on the analysis and selection of typical propulsion system such as hybrid propulsion with both the diesel propulsion and the electric propulsion with generators for several types of mainly offshore construction serving vessels. Access and expand information on vehicles and ships serving offshore construction, statistical methods, data processing combined with comparison and control to select the optimality typical propulsion system.

This chapter presents an overview of oil and gas investment and different types of offshore structures, from shallow water to deep water, and other structure configurations such as floating, production, storage, and offloading and tension-leg platforms. The offshore project phase, focusing on control of the engineering from appraisal, selection, definition, and execution, is discussed in this chapter. The offshore project investment and the cost estimate corresponding to each phase of the project are also discussed. To understand the oil and gas business, the first step is to define the offshore project target and objective, and then how to provide a project which is technically matched throughout all phases with the business requirements.

The relationship between digitalization, digital innovation, and digital transformation is an emerging topic in information systems (IS) research. Whereas IS researchers widely acknowledge that digitalization underpins both digital innovation and digital transformation, just how and by what mechanisms link digital innovation with digital transformation remains underexplored. Differentiating between ‘digital infrastructure innovation’ and ‘innovation in digital infrastructure’, this paper contributes towards current discussions by empirically elaborating how the open-ended and generative potential of digital innovation in practice has to be negotiated against the installed base of technical and organizational arrangements in digital transformation. We pursue this argument through a case study of digital innovation coordination in an inter-organizational digital innovation project with the goal of instigating digital transformation within the offshore construction industry.

Summary Objects within marine sediments pose a serious risk for offshore construction projects. Their detection is difficult with conventional geophysical methods. We present here a new data acquisition and processing strategy to detect and localize boulders through dedicated diffraction imaging. The new Manta Ray data acquisition system allows the recording of seismic data that is suitable for specialized diffraction imaging at depth. Seismic data processing using beamforming and synthetic aperture allows a high-resolution localization of diffractors in the sub-seafloor. The results may be used for the efficient de-risking of offshore construction sites with regards to glacial boulder locations.

The article tells about the risks of low-culture construction of oil facilities on the Arctic shelf. The long-term, practically neglected exploitation of the unique natural resources of the Russian North and the low culture of their development led in a number of its regions, including the waters of the Arctic seas with islands, to an emergency ecological situation - the partial and sometimes complete destruction of the fragile Arctic natural habitat of the small peoples of the North and the created cities and villages. Without proper environmental support, economic activities continue in the field of extraction, transportation and processing of natural resources. The progressive pollution of rivers and lakes leads to a qualitative depletion of water resources - a change in the composition of the waters of the Arctic Ocean. The danger of oil pollution of the marine environment is associated with plans for its production on the continental shelf of the Russian Federation. The oil and gas production complex in the Russian Arctic regions are being formed on the basis of already discovered fields and will develop as other promising fields are developed.

The fire performance of fiber-reinforced polymer composites used in naval ships, submarine and maritime structures are reviewed and discussed in this work. Polymer composites has been developed and used for wide range of applications in aircraft, spacecraft, boats, ships, automobiles, civil infrastructure, sporting goods and consumer products grown at an impressive rate over the last 50 years. In particular, the use of composites for naval vessels continues to grow in coming years for various applications including decks, bulkheads, propellers, propulsion shafts, pipes, pumps, and other machinery parts. Composites demonstrated as ideal materials in a wide variety of applications due to many outstanding physical, thermal-mechanical and chemical properties. Specifically, composites offers high specific stiffness and specific strength, low density, good fatigue resistance, outstanding corrosion resistance, excellent thermal insulation and low thermal expansion over many metal alloys. A major disadvantage of many composite materials is poor performance when exposed to high temperatures, in which the organic matrix decomposes with the potential to release of heat, smoke, soot and toxic volatiles. Offshore environment poses even more challenges for naval structure design, where fires although infrequent can have catastrophic effects due to their intensity and the isolation of the offshore construction. Although most of polymer composites are flammable, their resistance to pyrolysis can be improved.

Floating facilities such as, floating islands, floating houses, industries and, entire cities are constructions for habitation, entertainment, industrial or commercial purposes, and infrastructures...

Deep Cement Mixing (DCM) is the most commonly employed ground improvement method for offshore construction purposes worldwide. Nevertheless, the dynamic behavior of cement-mixed and stabilized clays is almost unknown due to the lack of experimental studies, while seismic concerns regarding offshore structures related to typhoons, tsunamis, or earthquakes are becoming more important. Moreover, very few geotechnical evaluations have been performed to characterize cement-mixed Korean marine clays, while DCM is the most commonly used practical implementation method for soft soil improvement in Korea. In this study, a series of laboratory experimental studies were conducted to obtain the static strengthening and dynamic behaviors and geotechnical engineering design parameters of cement-treated Korean marine clays. The unconfined compressive strength and shear stiffness (G) of cement-mixed Korean marine clay increase with curing time, while different trends were observed for straindependent behaviors (i.e. normalized shear modulus and damping ratio) depending on curing time and binder contents. The static and dynamic geotechnical properties and relationships of DCM treated soft clays obtained in this study are expected to be accepted for seismic considerations and designs of DCM-treated soft clays.

Grouted connections are structural joints formed by a cementitious grout cast between two concentric circular tubes. They are widely used in the offshore construction of oil and gas platforms, and for offshore wind turbines (monopiles and jackets). However, their application in offshore wind turbine installations can be critical due to the high bending moments coming from wind loading. Recently, it was found that grouted connections show limited performance in offshore wind turbine installations leading to settlements between the steel tubes and steel/grout debonding. Hence, structural health monitoring techniques for grouted connections are needed that ensure a safe and reliable operation of offshore wind turbines. This short communication describes the successful application of electromechanical impedance spectroscopy for damage detection in grouted connections.

Introduction. The 1969 Report of the UN General Secretary noted that 125 fixed platforms were used in offshore areas for the purpose of oil industry. “The International Law of the Sea” (Vol. 1 and 2) published in UK in 1994 provides that “approximately 6000 fixed platforms have been installed in offshore areas throughout the world”. In 2014 only in the area of the OSPAR Convention, 1992, more than 1300 offshore constructions were installed. As for January 2018, the majority of these constructions are in the North Sea (184), the Gulf of Mexico (175), the Persian Gulf (159), and offshore of Far East Asia (152) and Southeast Asia (152). In the other regions this number varies from 3 to 88, while the Canadian Arctic has the smallest number of offshore constructions limited to just 1 object. Accordingly, the issues of interpretation of UNCLOS articles on legal regime of artificial islands and other fixed structures at sea are becoming more pressing. Moreover, the interstate relations, regarding construction of artificial islands in offshore areas, need relevant legal framework to be in place, taking into account the constant growth of economic and military “competition” among countries, as well as the development of science and technologies applicable to offshore construction. Materials and methods . This paper dwells upon the international treaties and other legal instruments, which rely upon the terms “artificial islands”, “installations”, “structures” at sea for regulating relations among States and between States and other international law subjects. The materials for this paper are also commentaries of the UNCLOS, interpretation of the relevant articles of 1958 Geneva maritime conventions, applicable resolutions of the International Maritime Organization, and also definitions of the conventional terms suggested by scholars. The methodological basis of the research consists of general scientific and specific methods, including comparative method. Research results . Most specialists in the law of the sea who research similar topics dwell upon their personal definitions of the conventional terms mentioned above. Such specialists correctly note that the absence of such definitions in UNCLOS makes it difficult to interpret and apply relevant articles in a proper way. Meanwhile, the necessity for such interpretation and application is of practical value because such terms of UNCLOS relate firstly to relevant rights and jurisdiction of coastal and other States in maritime areas where artificial islands, installations and structures are used, including the territorial sea, the EEZ and the continental shelf. Nevertheless lots of different definitions of such terms suggested by scholars make it even more difficult to interpret and apply the rules of UNCLOS on artificial islands, installations and structures, including such sensitive areas of interstate relations as safety at sea and protection of the marine environment. Discussion and conclusions . The authors of this paper do not support any classification or definition of “artificial islands”, “installations” or “structures” or any other definition of other specific words used in UNCLOS for such terms. Instead the authors bring arguments to legal delineation of artificial islands from any other permanent structure at sea independently of the fact which particular word is used in UNCLOS for describing such a structure in a relevant article (“installations”, “structures”, “devices”, “equipment” etc.). It is argued in this paper that such legal delineation is caused by a difficult and comprehensive balance of interests achieved during the III Conference on the Law of the Sea, and such interests relating to economic, military, environmental interests of States, coastal and non-coastal, firstly in the EEZ and on the continental shelf.

This paper describes an experimental and numerical investigation of the Iberdrola TLP wind turbine concept, TLPWIND, in realistic wind and wave conditions. The TLP was coupled to the NREL 5 MW reference turbine and was designed to operate in a water depth of 70 m. The test campaign included free oscillation tests, tests in regular and irregular waves and simulated wind conditions. A Software-in-the-loop approach was adopted to account for the time-varying aerodynamic forces produced by the turbine during the physical experiments. The effect of wind was found to have a significant contribution to the overall response of the platform whilst variation in wave conditions was found to have a relatively small effect on the platform response. A comparison of results from physical and numerical simulations show that, the numerical predictions from FAST were very close to the results obtained from the experiments in some cases, but in other cases the numerical model failed to accurately predict the platform response. The results from both studies show the benefits of such TLP structures in terms of motions which are vital to obtain a high power output from a floating offshore wind turbine.

This paper develops a methodology to determine the installation costs of a floating wind farm installed offshore, the value of which depends on the type of floating offshore wind platform installed. In this context, several costs in the installation process have been defined: installation of the offshore wind generators, installation of the floating offshore wind substructures, installation of the anchoring and mooring, installation of the electric systems and the commissioning or start up of the floating offshore wind farm. Furthermore, several installation scenarios have been taken into consideration regarding the shipyard surface and draught, the number of lifts, the transport, the mooring strategy and the substation configuration. The method, tested for the region of Galicia and for three sorts of floating substructures: spar, semisubmersible and tensioned leg, allows to compare different alternatives of installing a floating offshore and the most important aspects of the costs proposed. It can be useful for investors who decide to use this type of offshore renewable energy in the future.

When a concrete-filled steel tube (CFST) is used in offshore construction such as electricity towers, bridges or platforms, it is subjected to continuous degradation during its service life due to the long-term in-service actions and the ocean corrosive environment . Fibre reinforced polymer (FRP) strengthening makes an effective solution to extending the service life of corroded CFST columns in existing offshore structures . For the rational design and tactful application of this corrosion strengthening technique, it is crucially important to understand the life-cycle performance of the strengthened column after experiencing the combination of multiple deterioration factors. In this study, an advanced finite element analysis (FEA) model, which is stage-by-stage verified against collected test data on 104 columns, is established to capture the nonlinear structural performance of FRP-strengthened CFST columns under coupled progressive degradation factors, i.e., initial imperfections , construction preload, sustained service load and corrosion. Corrosion of the steel results in less confinement on concrete and thus affects the loading capacity of the columns, while increasing the number of FRP layers can weaken the negative influence brought by multiple degradation factors. Based on parametric studies , a simplified design method is proposed for the ultimate strength prediction of corroded CFST columns strengthened by FRP.

Grouted connections have been widely used in offshore construction to connect two different-sized cylindrical steel tubes; these connections include pile-to-sleeve grouted connections for mono-piles of wind turbine towers and pile-to-jacket-leg grouted connections for jacket structures. Because the grouted connections in seawater are mainly subjected to environmental loadings induced by waves and wind loading, high-strength grouted connections have been widely applied in offshore structures to enhance the structural performance and to prevent fatigue failure generated by the cyclic environmental loading. In this study, the fatigue performance of high-strength grouted connections with shear keys subjected to unidirectional reversible cyclic loadings in dry conditions was evaluated based on experimental tests, numerical evaluations, and comparative analysis based on a test database established using prior studies. It was revealed that the grout strength, shear-key density, and stress ratio have a significant influence on fatigue performance. Finally, general aspects of effects of grout strength, shear-key density, and stress ratio that influence the fatigue capacity of high-strength grouted connections were discussed, and a design equation for the unidirectional cyclic loading condition in dry conditions was presented.