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The interaction between porous structures and flows with mean and oscillatory components has many applications in fluid dynamics. One such application is the hydrodynamic forces on offshore jacket structures from waves and current, which have been shown to give a significant blockage effect, leading to a reduction in drag forces. To better understand this, we derived analytical expressions that describe the effect of current on drag forces from large waves, and conducted experiments that measured forces on a model jacket in collinear waves and currents. We utilised symmetry and phase-inversion techniques, relying on the underlying physics of wave structure interaction, to separate Morison drag and inertia-type forces and to decompose these forces into their respective frequency harmonics. We find that the odd harmonics of the drag force mostly contain the loads from waves, while even harmonics vary much more rapidly with the current speed flowing through the jacket. At the time of peak force, these current speeds were estimated to be 40 % of the undisturbed current and 50 % of the industry-standard estimates, a result that has significant implications for design and re-assessment of jackets. At times away from the peak force, when there are no waves and only current, the blockage effects are reduced. Hence, the variation in blocked current speeds appears to occur on a relatively fast time scale similar to the compact wave envelope. These findings may be generalisable to any jacket-type structure in flows with mean and high Keulegan–Carpenter number oscillatory components.

Renewable energies are the future, and offshore wind is undoubtedly one of the renewable energy sources for the future. Foundations of offshore wind turbines are essential for its right development. There are several types: monopiles, gravity-based structures, jackets, tripods, floating support, etc., being the first ones that are most used up to now. This manuscript begins with a review of the offshore wind power installed around the world and the exposition of the different types of foundations in the industry. For that, a database has been created, and all the data are being processed to be exposed in clear graphic summarizing the current use of the different foundation types, considering mainly distance to the coast and water depth. Later, the paper includes an analysis of the evolution and parameters of the design of monopiles, including wind turbine and monopile characteristics. Some monomials are considered in this specific analysis and also the soil type. So, a general view of the current state of monopile foundations is achieved, based on a database with the offshore wind farms in operation.

Gluder discusses the equity and safety in polar oceanography. She highlights an opportunity for leadership to extend this strong advocacy for safety during field operations to an area that has historically been neglected: consideration of body sizes other than the \"standard male\" when equipping research ships with survival equipment. Immersion suits, flight suits, life jackets, and foul weather gear are commonly stocked as one-size-fits-all.

In recent years, the offshore wind industry has seen an important boost that is expected to continue in the coming years. In order for the offshore wind industry to achieve adequate development, it is essential to solve some existing uncertainties, some of which relate to foundations. These foundations are important for this type of project. As foundations represent approximately 35% of the total cost of an offshore wind project, it is essential that they receive special attention. There are different types of foundations that are used in the offshore wind industry. The most common types are steel monopiles, gravity-based structures (GBS), tripods, and jackets. However, there are some other types, such as suction caissons, tripiles, etc. For high water depths, the alternative to the previously mentioned foundations is the use of floating supports. Some offshore wind installations currently in operation have GBS-type foundations (also known as GBF: Gravity-based foundation). Although this typology has not been widely used until now, there is research that has highlighted its advantages over other types of foundation for both small and large water depth sites. There are no doubts over the importance of GBS. In fact, the offshore wind industry is trying to introduce improvements so as to turn GBF into a competitive foundation alternative, suitable for the widest ranges of water depth. The present article deals with GBS foundations. The article begins with the current state of the field, including not only the concepts of GBS constructed so far, but also other concepts that are in a less mature state of development. Furthermore, we also present a classification of this type of structure based on the GBS of offshore wind facilities that are currently in operation, as well as some reflections on future GBS alternatives.

Suction caisson jackets are promising foundation solutions for offshore wind turbines (OWTs) in deep water. The resistance of such a foundation against overturning actions depends on the uplift response of individual caisson. Winkler models (i.e., foundation displacement versus soil reaction relationships) have been shown powerful and efficient in modeling general soil–foundation interactions, whereas those targeting suction caisson subjected to tensile loading are relatively underdeveloped. The goal of this study was to construct a soil reaction model capable of accounting for site-specific soil stress–strain relations and project-specific foundation geometries. This objective is pursued via the concept of “inferred Winkler model” and by constructing soil reaction curves based on the outcomes of rigorous numerical modeling. First, finite element analyses (FEAs), in combination with a well-established hyperbolic soil model, are utilized to evaluate the soil reaction responses associated with vertically loaded caisson in undrained clays. The FEA then establishes the interrelationships between the key characteristics of soil reaction behavior, soil stress–strain relations, and foundation geometries, leading to an inferred Winkler model capable of directly utilizing soil model parameters. Lastly, the proposed soil reaction model is assessed against centrifuge test results and shown capable of reasonably representing test observations and delivering solutions comparable to FEA but at a much lower computational cost.

This paper compares two methods for retrofitting an existing hospital concrete structure to improve its seismic performance: internal and external retrofitting. Internal retrofitting involves adding chevron braces, reinforcing shear walls with Fibre-reinforced plastic coating, and wrapping the walls, columns, and beams using steel jackets. External retrofitting uses two braced exterior steel frames connected to the concrete building using dampers. The paper also proposes a new design objective for hospital structures that ensures immediate occupancy performance level under earthquake hazard level-1 and prevents collapse under higher ground motion intensity. The paper evaluates the base structure, the two retrofitting schemes, and the proposed design method using pushover and nonlinear dynamic analyses under 20 selected earthquake records. The paper then compares the probabilistic seismic risk models using fragility curves. The results show that external retrofitting is more effective and economical than internal retrofitting and that the proposed design objective can significantly reduce the seismic risk of hospital structures.

With the development of offshore wind turbines in deep water, suction caisson foundations jointly used with jackets have become a promising foundation type for those constructed in windfarms covered with soft soil. Reasonable prediction of the stiffness of suction caisson has a significant influence on analyzing both static and dynamic response of supported structures. Distributed spring-based Winkler models have been successfully constructed to evaluate the stiffness of pile and caisson foundations under vertical and lateral loading. However, the counterparts for suction caisson under general loading conditions (i.e., combined vertical, horizontal, and moment loading, V–H–M) are relatively under-developed, despite the latter representing one of the most fundamental working scenarios of the foundation. The goal of this work is to establish a simplified Winkler model capable of calculating stiffness of suction caisson foundation under combined loading (V–H–M) in non-homogeneous and layered soil. This purpose is achieved via the concept of “Inferred Winkler model.” In particular, we construct a special model structure that accounts for the distinct influences of foundation embedment and non-uniform distribution of soil reactions, while maintaining theoretical consistency with well-established Winkler models for pile and shallow foundations. Specific relationships and expressions in the above model are then inferred from finite element analysis (FEA). The performance of the proposed model is evaluated against FEA regarding both foundation response and soil reaction distributions under combined loadings in homogeneous, non-homogeneous and layered elastic soil. Reasonable agreement between the calculation results suggests that the proposed model is reliable for foundation stiffness assessments and has a much lower computational cost compared to FEA.

The shear resistance computed using Annex J of Part 1–1 of Generation 2 of Eurocode 2—on strengthening of RC members for static loads with externally-bonded Fibre-reinforced-polymers (FRPs)—exceeds by about 25% on average the cyclic shear resistance of 64 FRP-jacketed shear-critical RC specimens in the international literature. The semi-empirical cyclic shear resistance approach for FRP-wrapped RC members in Annex A of Part 3 of Generation 1 of Eurocode 8 is in good average agreement with the results of these tests, but conflicts with the rational, mechanics-based approach for shear resistance against static actions in Generation 2 of Eurocode 2, which has already been adopted in Generation 2 of Eurocode 8 for members without FRP jackets, adapted to the specific needs of seismic design. This latter approach is modified and extended to cover RC members with closed FRP jackets in a more technically sound way than in Annex J of Generation 2 of Eurocode 2. The new approach fits the available cyclic test results without bias or lack-of-fit with respect to the key variables controlling cyclic shear resistance, gives slightly better accuracy than the semi-empirical one in Generation 1 of Eurocode 8 and does much better in correctly identifying as not failing in shear FRP-wrapped RC members which have failed in flexure or not failed at all during cyclic testing.

A series of new synthetic armored cables were developed and tested to ensure that they were suitable for use with the RECoverable Autonomous Sonde (RECAS), which is a newly designed freezing-in thermal ice probe. The final version of the cable consists of two concentric conductors that can be used as the power and signal lines. Two polyfluoroalkoxy jackets are used for electrical insulation (one for insulation between conductors, and the other for insulation of the outer conductor). The outer insulation layer is coated by polyurethane jacket to seal the connections between the cable and electrical units. The 0.65 mm thick strength member is made from aramid fibers woven together. To hold these aramid fibers in place, a sheathing layer was produced from a polyamide fabric cover net. The outer diameter of the final version of the cable is ~6.1 mm. The permissible bending radius is as low as 17–20 mm. The maximal breaking force under straight tension is ~12.2 kN. The cable weight is only ~0.061 kg m−1. The mechanical and electrical properties and environmental suitability of the cable were determined through laboratory testing and joint testing with the probe.

The emergence of cementitious materials with post-cracking strain hardening stress strain response in tension presents opportunities for retrofitting reinforced concrete elements through the application of very thin jackets, a technique that preserves the original geometry of the component. This retrofitting solution is studied experimentally in this work by replacing the damaged cover of lightly reinforced structural elements, which were previously tested under cyclic displacement reversals, simulating earthquake effects. Test specimens were detailed to represent older construction practices, where inadequate lap splicing of longitudinal reinforcement, light transverse reinforcement and thin concrete covers were common. Upon cyclic loading of the retrofitted components, the contribution of the thin jackets to the strength and deformation recovery of the old type reinforced concrete elements was examined considering the pre-existing damage. It was found that the efficacy of cover replacement with strain-hardening composites is significant not only for strength recovery but also in terms of enhanced deformability of the retrofitted component. The experimental response envelope was simulated using advanced nonlinear finite element modeling to gain improved insights regarding the stress state in the cover-replacement retrofitting layer, and to explore the performance of this retrofitting method for parameter values beyond the range of the experimental program. The amount of confinement exerted by the strain hardening cover was related to the tensile strength of the cover material and it controlled the strength recovery. However, by suppressing all brittle modes of failure along the shear span of the component, the reinforcement anchorage in the footing dominated the eventual failure mode.