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Abstract In the processes of lowering down or raising up the legs of a floating structure, the legs are neither touch with the sea bed nor completely lift up, and the structure is situated in the condition of freely floating on the waves. The existing of the legs equipped on the structure leads to the property different hydroelastic responses from the ordinary floating structures. To investigate the variation of the length of the legs underwater affecting the hydroelastic responses, a plate-cell model is proposed, and the basin tests using the elastic model in waves are carried out. Based on the length of the legs under water, the model is set as 2 cases. The attenuation tests in calm water and test in the regular wave at zero speed in various of the wave conditions are carried out. According to the plate-cell model, a numerical model is constructed to simulate the hydroelastic responses of the 2 cases based on the theory of the three-dimensional (3-D) linear hydroelasticity. Both the experimental and numerical results demonstrate that the legs have significant influences on the hydroelastic responses of the structure. Highlights • A new hydroelastic experimental method is introduced for researches on floating structure with legs. • The significant influences of the length of underwater legs are investigated by experimental and numerical simulations. • Not only the conclusions of this paper, but also the experimental methods introduced in this paper have valuable references to relevant researches. [ABSTRACT FROM AUTHOR]

This study reports a multi-scale structural analyses of a mainline floating double carcass marine hose (nominal diameter 508 mm, length 10.7 m, design pressure 2.1 MPa, weight 4100 kg). A material change in the reinforcement cords of the traditional hose is proposed, from polyester and polyamide to hybrid aramid/polyamide cords, allowing an improvement in design, reducing weight and increasing flexibility. Two models have been developed to obtain the hose responses. Firstly, a finite element model of the traditional system was built to perform a macro-scale analysis of global hydrodynamics loads in the hose line using Orcaflex™ software. Then, a non-linear finite element model was developed for meso-scale analysis using Abaqus™ software. Rubber and cords were modeled using hyperelastic models, and axial, bending and torsional stiffnesses were evaluated. Experimental tests were carried out to assess the mechanical response of an actual full-scale hose. The reduced number of layers of the hose using hybrid cords, compared to the traditional one, allowed a reduction in weight of 15%, and brought also a decrease in specific axial, torsional and bending stiffnesses of 43.9%, 52.2% and 21.6%, respectively. The multi-scale analysis predicted well the structural response of the hose line, and the reduced potential failure may increase life-time of the structure. [ABSTRACT FROM AUTHOR]

The model test method of the FPSO and offloading system is investigated by using the development mode of “FPSO + CALM + TANKER” working in a 1700-m depth of offshore West Africa. An equivalent design based on static and dynamic similarity criteria for oil offloading line (OOL) is discussed, and a type of creative method for the equivalent design of OOL in a model test is proposed. Based on the static similarity criterion, the truncated design of the FPSO mooring system in water depth and horizontal directions is carried out. After that, a relevant static optimization is conducted. Meanwhile, to avoid interference between the FPSO mooring system and CALM mooring system, a horizontal equivalent design for the CALM mooring system is provided. On this basis, the model test scheme is conducted. Time domain coupled analyses for the whole system before and after truncation are later performed. After comparison, it is observed that the calculated results of the truncated system are basically consistent with those of the prototype system, and the design of the model test scheme is demonstrated to be robust and reliable. [ABSTRACT FROM AUTHOR]

Marine constructions modify physical conditions by interfering with water circulation and increasing sedimentation and pollution, leading to biological homogenization. However, they also increase the availability of hard substrata for larval recruitment, resulting in the development of a diverse sessile community and associated fish fauna. To describe how the modifications caused by a floating marina affect reef fish assemblages at São Sebastião Channel, SW Atlantic, a multiparameter probe and a visual census methodology were used to compare the abiotic conditions and the diversity and abundance of fishes between two areas: the area inside the marina where boats are moored and the breakwater, an area more similar to nearby natural rocky shores. The area inside the marina presented more turbid and productive waters, while the breakwater was more turbulent. The abundance of fishes inside the marina was greater than at the breakwater throughout the study, but species richness was higher inside the marina only during the hot and wet period (Austral Summer and Spring). Fish assemblages were strictly different between areas. Species dominance for each area and at nearby natural rocky reefs was also different. This study shows that artificial habitat causes micro-spatial modifications to local fish assemblages. As spatial variations were related to the behavioural and ecological aspects of fishes, marine facilities should be carefully planned, and engineering principles should be combined with ecological processes to better resemble natural habitats, thereby reducing environmental impacts. [ABSTRACT FROM AUTHOR]

A semi-floater concept as a substructure for multi-megawatt wind turbines is developed herein for installation at 50+ m water depths. The semi-floater concept is a hybrid between a fixed monopile type support structure and a floating spar buoy. The configuration of the substructure is composed of a floating system, a mooring system, and an articulated joint. A case study is carried out under specific design conditions and constraints. The detailed designs of the mooring system and of the articulated joint are iteratively carried out using a hydro-servo-elastic analysis tool for structure response, HAWC2, coupled with dedicated in-house software packages for structural design analysis, and Abaqus. A reliability analysis and fatigue load calculations are made to ensure a desired life expectancy of the structure. The semi-floater concept is shown to maintain acceptable fatigue load levels for all turbine components, and to exhibit low platform displacement at the mean sea level. Finally, the overall performance of the structure related to energy production is similar to that of a reference wind turbine situated on land. [ABSTRACT FROM AUTHOR]

This study presents data on abundance and density of macro-floating marine debris (FMD), including their composition, spatial distribution and potential sources off continental Portugal. FMD were assessed by shipboard visual surveys covering ± 252,833 km 2 until the 220 nm limit. The FMD average density was 2.98 items/km 2 and abundance amounted to 752,740 items. Unidentified plastics constitute the major bulk of FMD (density = 0.46 items/km 2 ; abundance = 117,390 items), followed by styrofoam, derelict or lost materials from fisheries, paper/cardboard and wood material. The North sector of the area presents higher FMD diversity and abundances, probably as a result of the high number of navigation corridors and fisheries operating in that sector. Most FMD originate from local sources, namely discharges from vessels and derelict material from fisheries. Considering the identifiable items, cables and fishing lines were the only fishing related items among the top ten FMD items in Portuguese offshore waters. [ABSTRACT FROM AUTHOR]

Marine litter is one of the descriptors in the European Marine Strategy Framework Directive, which aims to achieve a healthy marine environment and make ecosystems more resilient to climate change. Most experiences have been focused upon quantifying the abundance and distribution of marine litter, on beaches in particular. Nevertheless, the continuous impact of litter on marine species, commercial activities, i.e. shipping and fishing, and the local economy are prompting scientist and stakeholders to identify additional approaches required to face this challenge. This contribution addresses the aforementioned need, by assessing the possibility of fishing vessels shifting from fish to floating marine litter (FML), during low fishing activity periods. For this purpose, the technical, environmental, and socio-economic feasibility of such a change is investigated. The technical assessment includes: the analysis of energy consumption; and the assessment of ocean surface current patterns as a tool to determine FML convergence hotspots. The environmental feasibility is analysed by a Life Cycle Assessment study of 3 FML management scenarios. The minimum subsidy required is analysed in the socio-economic assessment, in order to reach a profitable diversified activity. The results demonstrate fishing FML as a technically-, economically- and environmentally-viable activity. Nevertheless, Local Authorities need to encourage the prevention of FML arriving on shore where, in some environments, such as in rocky shores, cleaning is difficult. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a preliminary technical and economic evaluation for a new concept, the Floating Container Storage & Transhipment Terminal, or ‘FCSTT’. The main purpose of the FCSTT is considered to handle transhipment traffic, although its use could extend to supporting existing land-based terminals within ports. The paper considers a range of floating port structures already in operation, and other concepts yet to be developed. To an extent the FCSTT, which is based on conversion of a large container vessel, is an extension of these and other developments in different shipping sectors. The FCSTT can handle container cargo in offshore locations and/or wherever there is a need to provide ‘terminal’ infrastructure rapidly and at low cost. Our approach outlines design options for a FCSTT including analysis of crane preferences. The paper includes analysis of required storage capacity, and container handling productivity levels sufficient to ensure a practical terminal that is comparable with any landside facility, albeit with a focus on transhipment traffic. Thereafter the capital and operating costs for the FCSTT are estimated, with forecast cash flows based on assumed traffic volumes and competitive handling rates. Conclusions suggest the FCSTT offers potential for significant capital and operating cost savings compared to higher cost landside terminal infrastructure. Other key factors and advantages, including areas for further research, are highlighted. [Copyright &y& Elsevier]

Abstract: Steep wave impact pressures and the structural dynamic response of floating production storage and offloading platform (FPSO) bows are studied using 1:80 scale segmented, instrumented models. The construction of these segmented models is discussed. The ‘new-wave’ theory is adopted and extended to generate steep waves and a limiting form of steep wave that might be found in deep water is proposed. A comparison between linear theoretical, experimental and suggested wave models is made. Experimental results with systemically varying parameters are presented. [Copyright &y& Elsevier]

Abstract: In the early stages of the selection process for the hardware to exploit an offshore petroleum reservoir, it is important to be able to identify rapidly which production facility type(s) are likely to deliver the greatest value. This paper explores key features and constraints of the ten common fixed, floating and subsea facility options. Both shallow and deepwater are considered, along with regional variations. It is shown that facility applications may be categorised in a very simple matrix form, with the water depth and well count being particularly important drivers of facility choice. [Copyright &y& Elsevier]