This paper studies the fixing modes of netting system for the fully submerged aquaculture cage. Through physical model tests, the forces on column-netting structure model's tie points for different current velocities and different fixing modes were measured. The influence of netting fixing modes on the forces on test netting tie points are analyzed. And through photographing of test process, the deformation law of test netting was obtained. Furthermore, in order to study the influence of netting fixing modes on tension distribution of the netting in column-netting structure model, this paper numerically simulates the netting based on the lumped mass method. Through numerical simulation, the tension distribution characteristics and load transfer mode of the netting under different current velocities and different netting fixing modes are analyzed. INTRODUCTION With the development of marine aquaculture industries in the direction of open ocean and large-scale, China began to design and construct the large-scale fully submerged aquaculture cage that can cope with complex sea conditions. Flexible netting is the main part of the largescale cage (see Fig. 1). It plays a significant role in maintaining space for fish growth, preventing fish escape and other animal attacks, and keeping water exchange inside and outside the cage. The safety and reliability of netting is directly related to the economic benefits and sustainable development of aquaculture production. Different from the traditional gravity cage, the netting system of fully submerged aquaculture cage is fixed around a steel frame. Under the action of current, the deformation of netting is small. However, different fixing modes affect the distribution characteristics of netting. Therefore, it is of practical significance, under the action of current, to study the effect of different fixing modes on hydrodynamic characteristics of netting. In recent years, many scholars have done a lot of research on the hydrodynamic characteristics of cages. Lader et al.(2005) tested a scale model of a flexible circular netting with different weights attached to the bottom in a flume. Global forces and netting deformation were measured for different steady current velocities. Lader et al.(2006) investigated the dynamic properties of a flexible netting sheet exposed to waves and current using a numerical model. The hydrodynamic loads acting on high solidity net cage models subjected to high uniform current velocities and the corresponding deformation of the net cages are studied by Moe-Føre et al.(2015). In the research of large-scale aquaculture cages, Wang et al.(2019) used the method of water elastic deformation and the method of treating cages as rigid structures, and numerically simulated the hydrodynamic performance of deepwater cages under the action of waves. Zhao et al.(2019) investigated the hydrodynamic responses of a semi-submersible offshore fish farm (SalMar., 2018) in waves, through a series of physical model tests.

Fish resource is sustainable, cheap and available to people worldwide. It can be harvested efficiently by using aquaculture. Recent trend is using a large offshore structure for fish farming in deeper seawaters. The present study focuses on the experimental measurements on the structural behavior of a semi-submersible and flexible structure under the currents and waves. In the experiment, the overall structural deformation is measured by using the optical tracking system while the strains are measured at various locations by using strain gages. It is found out that the structural response of the semi-submersible structure under co-existing waves and current is not equal to the sum of the responses due to waves and current, respectively. INTRODUCTION The world population is increasing. One must consider a fact that more people will eat more fish in the future. The fish resources need to be developed to meet the expanding demand for food. Fish farming or aquaculture may give a solution to it. In 2008, the aquaculture provided 46% of the fish produced globally for human consumption with a mean yearly increase rate of 7% since 1970. Thus, the development of the aquaculture is in line with Sustainable Development Goals (SDGs) adopted at United Nation Summit in 2015. Fish resource can be sustainable, cheap and available to people worldwide, but, still the technology is at the developing stage. Currently, researchers are discussing to adopt a large offshore structure for fish farming in deep seawaters, distant from coastal area (Aksnes, 2017, Engelhaupt, 2007, Fore et al, 2018). One pioneering pilot project of the offshore aquaculture is already initiated in Norway (Figure 1, Sal Mar 2016). By using the large offshore structure, fish aquaculture may be performed much more efficiently due to the size economy, in a cleaner area. It poses other challenges since the seas in offshore is much harsher than the coastal area, in general; higher waves, higher sea current, deeper water depth, large distance from shore, etc. Meanwhile, the structure becomes relatively flexible due to its size. One concern is how the structure may behave in the sea current and waves (Ma, et al, 2016, Takagi, et al, 2011).

A trapezoidal large floating structure discussed in this paper is one of modules of a hexagon accommodation platform which provides life accommodation, ship docking and marine supply in deep ocean. The trapezoidal large floating structure is a typical flat structure that the ratio of ship width and depth is very large so that its 3D hydroelastic response involving bending and torsion is significant. A model test for the trapezoidal large floating structure was carried out in this paper to study its load and response characteristic. Firstly, the test model of structure was designed which was made up of foam layer and plate layer, foam layer provided buoyancy and displacement while plate layer gave structural strength and deformation. Then a number of sensors measuring displacement, strain, and pressure were arranged on the model. Thirdly, a number of wave cases were determined to be generated in a tank. Lastly, the model test was performed in tank waves, a lot of time-domain research results were obtained, then frequency-domain results were analyzed. Hydroelastic mechanism of the trapezoidal large floating structure was analyzed based on these experimental results. INTRODUCTION With the rapid development of the marine economy of China, there is an urgent need for the protection support of very large floating structure (VLFS). The scale of the very large floating structure is huge and it can be stitched together by multiple modules, serving as an integrated support platform for marine development, which provides life accommodation, ship docking and marine supply in deep ocean. The trapezoidal large floating structure discussed in this paper is one of the modules of a hexagon accommodation platform, which is different from the traditional ocean floating structure, and is a typical flat structure, which is relatively rigid and the elastic deformation of the structure dominates. Therefore, the traditional hydrodynamic theory based on the hypothesis of rigid body motion is no longer applicable to very large floating structure, and the theory of hydroelasticity should be considered to evaluate structural response in waves.

In this paper, based on the idea of two-parameter model of bond-based peridynamics (BB-PD), the formulas of bond force is derived, and the tension and simple shear of plate are simulated by the derived form of bond force. Then the time step and the corresponding parameters of the model under the quasi-static algorithm and dynamic relaxation algorithm are derived,respectively. The two algorithms are applied to the simulations, respectively. By conducted two typical simulations It is proved that the two-parameter model can solve the problem of fixed Poisson's ratio, and the correctness of formulas of bond force and parameters in calculation. INTRODUCTION When dealing with the crack problems, the peridynamics (PD) is calculated by the integral equation, which avoids the shortcomings of discontinuity equation of the traditional continuum mechanics at the crack (Silling,2000; Silling and Askari,2005). However, BB-PD is only related to bulk modulus when simulating linear elastic materials, so that the Poisson's ratio is fixed to 1/ 3 for plane stress problems, and 1/ 4 for plane strain and 3D problems. It is impossible to accurately simulate problems with the arbitrary Poisson's ratios. The fixed Poisson's ratio has so much limits, when solving the practical problem. Therefore, the state-based peridynamic was proposed (Silling, Epton, Weckner, Xu, and Askari,2007). There is no problem of the fixed Poisson's ratio in the state base. However, the state-based peridynamic is more complicated than the bond-based peridynamic. Therefore, domestic and foreign researchers have done a lot of research on solving the problem of fixed Poisson's ratio. Gerstle, Sau and Silling (2007) proposed the micro-polar model, which adds a pair of moments based on the original bond force. However, the model needs to process a large amount of calculation in actual use, and it does not give a clear potential energy function. Prakash and Seidel (2015) proposed the twoparameter linear elastic peridynamic model. Two coefficients of springs were introduced to describe the displacements in the normal and tangential directions to solve the fixed Poisson's ratio problem. Similarly, Zhu and Ni (2017) considered the shear deformation in the BB-PD model of the bond. By introducing the rotation effect of the bond, the bond force between the two material points can be decomposed into normal and tangential components, and the energy of the bond can also be divided into tensile energy and shear energy. In fact, the twoparameter models proposed by Prakash and Seidel (2015) and Zhu and Ni (2017) are the same models in theory, except that the definitions of the potential energy functions are different, which resulted in the different final forms of coefficients. Diana and Casolo (2019) summarized several theoretical hypotheses of bond and proposed corresponding solutions. And a micro-polar model considering shear deformation of bond and failure criteria for shear deformation was proposed.

This article describes the further development of the author's method of ice loads dynamic calculation, outlined earlier in the articles (Bolshev and Frolov, 2012, 2016, 2018, 2019). Ice loads are calculated using mathematical simulations of the dynamics of ice and structures in time domain. The structures can have both a straight and reverse slope forming. Simulation of the ice formations and structures interaction is made for a wide range of ice characteristics and structure parameters. Special model tasks of ice destruction are considered. INTRODUCTION The main difference between this technique and other methods of ice load calculation is the use of a two-dimensional ice model based on the theory of medium thickness plates, which allows to increase the computational efficiency of calculations significantly. The mathematical model takes into account the final deflection of the ice field and its immersion in water, the gradual plastic destruction of ice on individual ice sheets, the accumulation of ice floes under or above the ice and many other interaction effects with sufficient accuracy. The characteristics of plastic destruction are obtained by solving of special model tasks. All of these models are combined into one algorithm to describe the behavior of ice fields and structures. The described methods and algorithms are implemented in the "Anchored Structures" program. The article provides some of comparative results that confirm the validity of the methodologies presented. PROBLEM STATEMENT AND LIMITATIONS The main purpose of this technique development is to create a calculation tool (computer program) that allows you to make a mathematical simulation of the structure/ice dynamical interaction for a real time not exceed a few minutes by using of an ordinary personal computer. To achieve this effect, unlike conventional FEM methods, it was decided to abandon the three-dimensional ice model in favor of a two-dimensional. In this case, bending deformations and strengths are imitated with the help of special moment springs placed between the elements.

Consolidation settlements of a dual suction anchor (DSA) functioning as foundation structure (FST) of a pipeline end manifold (PLEM) on a soft clayey seabed during different installation and operational stages is evaluated. 3D finite element model of the DSA, including time intervals between installation phases, was created. The results showed the feasibility of DSA as the foundation structure of heavy subsea structures on very soft clays. It was observed that the maximum lateral deformations in the soil develop at shallow depths adjacent to the outside of the skirts, and the maximum vertical displacements occur in the soil plug inside the DSA and adjacent to the skirts. Concentration excess pore pressure was observed around at the tip of the skirts and adjacent to the stiffeners. In addition, it was found that the presence of post-lay rock at the vicinity of DSA considerably affects the settlement of DSA. INTRODUCTION Troll is a gas and oil field in the northern part of the North Sea, about 80 kilometers north-west of Bergen. The field is situated in the blocks 31/2, 31/3, 31/5 and 31/6 and the water depth in the area is 300 to 335 meters. The gas in Troll East is recovered by pressure depletion through 39 wells drilled from Troll A. The gas compression capacity at Troll A was increased in 2004/2005, and again in 2015. In addition to gas from Troll East, gas from the Troll B and C platforms is exported via the Troll A platform. The gas and natural gas liquids are transported from Troll A to Kollsnes Gas Processing Plant in Øygarden via three 36″ pipelines. The oil is transported from Troll B and C in pipelines to Mongstad. The Troll Phase 3 development (stage 1) is a 36’ subsea pipeline tie-back of two templates (W1 and W2) to the Troll A platform (see Fig. 1). Out of three initially proposed foundation structure (FST) alternatives, i.e. a rectangular foundation with peripheral skirts (Størkersen, 2016), a fourbucket suction anchor (Bertrane, 2010) and a dual suction anchor (DSA), the DSA was selected as the best foundation alternative for a pipeline end manifold (PLEM) on a soft clayey seabed. It was found that the DSA has advantages, such as providing a stiffer mainframe structure, keeping the periphery of the suction anchors within the frame extents and providing simple suction system arrangements compared with the four bucket solution, and a better control of installation and leveling process compared to the rectangular skirt solution. TrollWest DSA was installed successfully in July 2019 (see Fig. 2).

Submarine-pipeline developments are moving into deeper waters. As a result, thicker pipe walls are needed and hence the quotient of the pipe diameter and its wall thickness (i.e., D/t ) reduces. On the other hand, there is a push to optimise properties and requirements for moderate water depths of several hundred metres. Design criteria in the prevailing submarine-pipeline design standard DNVGL-ST-F101 (2017) were developed for straight pipes with 15 ≤ D/t ≤ 60 but applicability is limited to D/t ≤ 45. There can be a desire to go beyond this limit when designing for moderate depths. When pipe walls are becoming thinner, this makes the pipeline more susceptible to collapse. It has been found that, in some cases, the DNVGL-ST-F101 formulations that aim at predicting the collapse pressure of relatively thin-walled pipelines can lead to nonconservative results. This is a concern when the line-pipe manufacturing technique employs cold forming—such as the cross-section expansion step in the UOE and JCOE methods—and the adverse contribution of the Bauschinger effect is not mitigated in a suitable manner. INTRODUCTION The UOE and JCOE methods are used for manufacturing largediameter seam-welded line pipe. Both methods include a coldexpansion step, which can promote the Bauschinger effect. The pipe's compressive stress–strain curve can be affected in two different ways: (1) the plasticity plateau can be lowered (i.e., a reduction of the yield stress), and (2) the curve can become more rounded near its transition from linear-elastic to plastic behaviour. Current design formulations were derived after assuming bilinear (elastic-perfectly plastic) relations between stress and strain, and deal with only the first effect, via the fabrication factor. The second effect can cause significant narrowing of the range in which the material behaves linearly and is particularly pronounced for steels that are not subjected to (light) heat treatment after cold forming. The collapse mechanism is a typical design driver for pipelines in deep and ultra-deep water. However, it can also be important for pipelines in intermediate water depths. Collapse is the failure mode where the pipe cross section becomes unstable due to excessive external pressure acting on the pipe wall. It is typically viewed as buckling or bifurcation behaviour because the cross section will deform significantly only when the acting pressure is very close to the limit capacity. In this range of pressure, a very small pressure increase will result in a relatively large growth of deformations. When the cross section cannot sustain any more pressure increase, it will ovalize excessively and ultimately flatten: this is called collapse.

In lab-scale model tests of modular floating structures, motion measurement is sensitive to mechanical influence of contact-based measurement systems. To investigate alternatives, model tests of a modular flexible floating structure interacting with regular waves was carried out in the towing tank of Delft University of Technology. Non-contact 3D digital image correlation (3D-DIC) technique was employed to evaluate the structural displacement. Stereovision based system Optotrak Certus of Northern Digital Inc., which relies on cable connection to the model, was used as a reference system to validate the DIC results. Model motions were analyzed and compared between the two systems. Comparisons show that DIC results agree well with stereovision results, indicating that the DIC system is an accurate motion measurement of floating structures in waves. INTRODUCTION Very Large Floating Structure (VLFS) is regarded as an alternative to land reclamation for ocean space utilization with various applications, such as floating bridges, floating airports, floating fuel storage facilities, and floating cities (Wang and Tay 2011). A typical feature of VLFS is a large length-to-thickness ratio because its horizontal dimensions are usually several hundred to thousand meters, while the vertical one is only a few meters. Such structure has apparent flexible body responses rather than rigid body motions under wave actions. Therefore, analyzing the hydroelastic response of wave-VLFS interaction is of great importance. The hydroelastic response of the VLFS is often studied to determine the deflection of the VLFS under the action of wave forces and also measure the influence of the floating structure on water waves. Extensive research on this problem has been carried out both theoretically and experimentally. Several methods for calculating hydroelastic response have been proposed, and those can be roughly categorized into mode superposition method (Newman 1994; Wu et al. 1995; Kashiwagi 1998a; Abul-Azm and Gesraha 2000) and direct coupling method (Hermans 2010; Kashiwagi 1998b; Namba and Ohkusu 1999; Ohkusu and Namba 2004; Taylor 2007). The mode superposition method consists of separating hydrodynamic analysis from dynamic response analysis of the structure and structural deflection is represented generally by superposition of finite eigenmodes. The direct coupling method solves the coupled equations of structure deflection and wave pressure/velocity potential directly without expanding structure motion into eigenmodes. Other numerical solutions e.g. BE-FE combination method (Utsunomiya et al. 1995; Liu and Shigeki 2002), and a method that divides continuous VLFS into rigid modules connected with elastic beam elements (Lu et al. 2019) were also developed. However, most predictions are expressed within the scope of potential theory.

At present, there is no ripe experience of settlement characteristics and calculation of soft foundation in offshore immersed tube tunnel. In this paper, rebound and recompression modulus of the natural foundation of immersed tube tunnel are studied by laboratory consolidation and rebound test. The law of soil rebound and recompression deformation changing with loading is revealed. INTRODUCTION With the rapid development of port engineering and construction technology, the immersed tube tunnel will become the main way of cross-river and cross-sea project. To ensure the construction quality and operation safety of immersed tube tunnel, the requirements of installation precision and settlement control are very strict. Normally, the tunnel is placed in the excavated foundation trench, then, the trench is backfilled and the tunnel is locked. The foundation soil experiences the process of unloading and reloading. Therefore, the accurate calculation and characteristic analysis of rebound and recompression settlement of tunnel foundation are very important to ensure the safety of immersed tube tunnel. In recent years, many scholars have carried out research on the resilience of foundation excavation. Duncun (1970) carried out the finite element calculation of foundation heave by using the curve model. S.K.Bose.N.N.Som (1998) used two-dimensional finite element method to simulate excavation process by steps of foundation and the change of support mode. Pan Linyou and Hu Zhongxiong (2002) put forward the concept about the range of rebound area and strong rebound area. Li Jianmin and Teng Yanjing (2010) proposed the concepts of reloading ratio and recompression ratio through the rebound and recompression test and model test of a large number of soil. And they also obtained the basic law of soil recompression deformation. Xv Gancheng and Li Yongsheng (1995) calculated the rebound deformation caused by excavation with different formulas. Although the above scholars have carried out the systematic study on the soil rebound and recompression problem, however, there are few studies on the rebound and recompression of immersed tube tunnel foundation soil under special working conditions. Because of the regional difference of foundation soil, this paper is based on the immersed tube tunnel foundation of the Hong Kong-Zhuhai-Macao bridge. And the study on deformation characteristics and law of soil rebound and recompression are carried out.

Tension leg platform (TLP) foundation piles could experience excessive lateral deformation induced by extreme TLP offsets which might jeopardize the structural integrity. Provision of fins onto pile top is evolving as an alternative to improve pile lateral performance. This paper presents suites of three-dimensional (3D) finite element analyses of the laterally loaded top-finned TLP foundation pile to evaluate the lateral pile behavior and efficiency of fins in comparison with regular pile. Advantages of the top-finned pile in structural design are described. Additionally, loading directional effect on lateral response of the topfinned pile is discussed. The results indicate that usage of fins could significantly increase pile lateral resistance by 77%, and consequently could save pile material take-offs by 39%. The current study demonstrates that provision of top fins is a viable and promising alternative which can improve the lateral performance of TLP foundation piles and provide pile cost savings. INTRODUCTION A tension leg platform (TLP) is a vertically moored floating facility typically used for deepwater oil and gas production. The buoyant hull is tethered to the seafloor foundation by vertically oriented tendon clusters at each corner of the structure. The tendon system with high axial stiffness rigorously restrains vertical motions of the TLP; however, it allows horizontal offsets to a small percentage of water depth. The foundations for TLPs usually consist of large-diameter driven pipe piles that provide resistance to sustain tendon tensions. The TLP foundation piles are typically long flexible cylinders (i.e., with diameter of 2 m to 3 m and length of 80 m to 140 m), with slender ratio (L/D) greater than 30. Fig. 1 presents the foundation pile make-up of Magnolia TLP introduced in Tang, et al. (2005), which was installed in Block 783 in the Gulf of Mexico with a water depth of approximately 1,425 m. It represents a typical configuration of TLP foundation piles, which are normally assembled by segments of drive head, tendon receptacle, conical transition, main sections and drive shoe. It has an outer diameter (OD) of 2.44 m and an overall length (L) of 103.1 m, with a stepped wall thickness (WT) profile.

The world's demand for energy is growing everyday and special attention is being given to sustainable energy sources like wind energy. This leads to the need for implementation of offshore wind turbines. In German sea regions, the water depths are predominately between about 20.0 m and maximum 50.0 m. Here, the cyclic loading by wind and waves leads to cyclic loads acting on the foundation. At the time being, in most cases monopile foundations are applied. However, for certain subsoil conditions also a gravity base foundation might be suitable and economic. Offshore support structures are exposed to millions of load cycles during their service time. Under such high cycle numbers, accumulated permanent deformation may affect the serviceability of offshore support structures. In particular, the accumulated rotation of the foundation structure is crucial regarding serviceability proofs of offshore wind turbines. The objective of this paper is to investigate the applicability of the ‘stiffness degradation method’ (SDM) to predict the behaviour of gravity base foundation under cyclic loading. The SDM uses the results of cyclic triaxial tests to account for the cyclic soil behaviour in a numerical simulation with the finite element method. This approach was initially developed to describe the behavior of monopile foundation systems. The method and its adaptations for gravity base foundations are briefly described. The measurements at a full-scale prototype of the gravity base foundation conducted a few years ago are utilized as a benchmark problem. Based on the comparison of the SDM results to the measurements, hints and recommendations regarding the application of SDM to gravity base foundations are given. INTRODUCTION In the North Sea and the Baltic Sea in Europe a large number of offshore wind farms are being planned and several farms have already been installed in the recent years. In the beginning, in most cases wind farms were erected in moderate water depths (less than 20.0 m) and monopile foundations have been built as support structures for the wind tower and the turbine.

In the near future, the Nankai Trough earthquake is expected to occur in Japan. It may not be received by the rescue and support from the land in the event of a disaster since the Kochi Prefecture is surrounded by steep mountains. Therefore, Kochi Prefecture has placed earthquakeproof berth, but we propose that fishing ports also be used as disaster prevention bases. In this study, we investigated the liquefaction countermeasures for fishing port quay using sheet piles. As a result, ①It finds out that the construction method using sheet piles is not enough for liquefaction countermeasures. ②The method using sandbags and permeable steel sheet piles confirmed the effect of suppressing liquefaction. INTRODUCTION The Pacific coast of Tohoku Earthquake on March 11, 2011 is the largest earthquake in the observation history around Japan, caused huge damage by tsunami and liquefaction. All port of Pacific side from Hachinohe Port in Aomori Prefecture to Kashima Port in Ibaraki Prefecture were damaged. Several damages such as settlement of structure and large faulting between the quay were seen in the damaged port. But fishing ports and harbors contributed greatly to recovery after the earthquake because the port function was quickly restored. The probability of the Nankai Trough Earthquake to occur within the next 30 years is estimated to be between seventy and eighty percent. When the Nankai Trough Earthquake occurs, there is a risk of damage to a wide area from Kyushu region to Tokai region. After the earthquake, Kochi prefecture may have difficulty receiving help such as transportation of supplies from the land route as it is surrounded by steep mountains. There are 88 fishing ports in Kochi Prefecture, part of the fishing port is considered to be at the time of the earthquake will be used as disaster prevention centers as well as the Tohoku region Pacific Ocean earthquake. Currently, seismic reinforcement and maintenance of several fishing ports, which are disaster prevention bases, are forwarding.

The study on viscous-dominated flow-structure interaction (FSI) now trends towards to be popular by using the modern CFD and CSD technique, that concerns in a board range of applications for ship and ocean engineering. For example, CFD and FEA are coupled to predict the dynamic behaviour of a flexible barge in regular head waves, including the hydroelasticity of a large containership and the deformation of a thin flat plate in air flows. The particular phenomenon of interest in this paper involves scattered data interpolation on the interface between the solid and liquid by introduction of the radial basis function (RBF) technology. Additionally, the RBF-based interpolation is optimized and improved according to the region decomposition technology and the error estimate of the RBF, which helps to effectively solve the large full-rank matrix connected with the RBFbased interpolation. In this way, a new data-independent RBF interpolation point selection method is developed. Three typical cases are given by using the global RBF interpolation, the compactly supported RBF interpolation and the partitioned RBF-based interpolation, in which we analyse the bending deformation of the flat plate under the impact of airflow, which is the representative of the FSI problems. By comparison, our developed partitioned RBF-based interpolation shows the global efficiency and accuracy. In particular, the relationship between the error estimate of the RBF and the filling distance of the interpolation domain is well verified. Probably, it provides a new simple approach for data exchange in FSI. INTRODUCTION Destructive problems have arisen in many flow-structure interaction phenomena, such as fatigue failure of propellers, failure of elbow erosion, damage to high-rise buildings by strong winds and bridge deformation due to sea waves. These problems seriously threaten product life and building safety. These problems now are widely solved numerically using the partitioned coupling method due to its efficiency. In the partitioned coupling solution, independent fluid and structural modules can be used respectively. It was verified (Su, 2010; Zhang, 2017) that, fluid-solid modules can help to take advantage of the existing CFD and CSD study within this frame, which usually show different spatial-temporal discrete methods. Thus, it is necessary to develop a high-precision and efficient interface transfer algorithm on the interface between the flow field and the structure field.

Anchors are indispensable and important structures in ocean engineering. The majority of previous studies on anchors were mostly based on Finite Element Analysis, but the large deformation of soil was not well handled. This study applied smoothed particle hydrodynamics (SPH) to simulate the anchor which buried in the soil. In this calculation, soil is modeled as elastic-perfectly plastic material, and the Drucker-Prager yield criterion is applied to describe the stress states of soil. Simulation test of anchor moved in the soil is calculated as a challenging example to verify the broad applicability of the SPH method. This study verified the feasibility of SPH in the numerical study of anchor and the results were encouraging. INTRODUCTION Anchor is one of the most widely used safety equipment in many fields such as Marine engineering and civil engineering. By burying the anchor in the soil, the anchoring strength is obtained, thus providing safety guarantee for Marine engineering and civil engineering. When external drawing force is too large, the anchor will be dragged in the soil and the large deformation of soil will occur. Once the soil deformation is too large, the anchoring effect of anchor will fail, and then a great threat to the safety of the engineering practice will emerge. Selecting the anchor with enough holding force is the necessary premise to ensure the safety of the project, and accurately measuring the movement and force of the anchor in the soil is the necessary premise to select the appropriate anchor. In the past, the research on anchor mostly used the finite element method (FEM), but the finite element method which based on grid can not effectively deal with large deformation. The mesh of FEM may distort severely and must be remeshed periodically when dealing with the large deformation and post-failure movement. SPH is mesh free Lagrangian particle method, which particles carry all the states: velocity, position, acceleration, etc. It can well deal with the large deformation of soil. SPH was originally proposed for astrophysical applications (Lucy, 1977 or Gingold and Monaghan, 1977).Since then, It has developed rapidly and successfully applied in many fields such as dynamic response of material strength (Libersky and Petschek, 1990; Libersky, Petschek, Carney, Hipp and Allahdadi 1993;Benz and Asphaug, 1995), free surface fluid flows (Monaghan, 1994), low-Reynolds number viscous fluid flows (Takeda and Miyama, 1994; Morris, Fox and Zhu, 1997), incompressible fluid flows (Cummins and Rudman, 1999; Shao and Lo, 2003), heat transfer problems (Clear and Monaghan, 1999), multi-phase flows (Monaghan and Kocharyan, 1995; Monaghan, 1997; Morris, 2000), geophysical flows (Gutfraind and Savage, 1998; Cleary and Prakash, 2004), turbulence flows (Monaghan, 2002), seepage failure flow (Maeda and Sakai, 2004) and elasto–plastic soil (Bui, Fukagawa, Sako and Ohno, 2008).

One of the challenges in bridge design is to ensure bridge girder integrity under accidental collision loads induced by the superstructures of drifting ships. Such accidents can happen either during earthquakes or tsunami inundations when ships are drifted. Accidents may also occur due to human errors in ship manoeuvring or technical failures. The collision accident may induce girder damage and compromise the safety of the bridge. Severe collision-induced structural damage may also lead to the collapse of the whole bridge. Among all collision incidents with bridge girders, shipping containers collision have not been investigated before. In fact, the containers piled on the ship deck can impose considerable impact loads on bridge girders. Therefore, this study aims to numerically investigate shipping container impacts with bridge girders. The impact demand of a single shipping container is first obtained through rigid indenter impact simulations. The effect of the impact angle is also discussed. Next, the impact response of shipping containers considering the arrangement, boundary condition, and interaction between adjacent containers are discussed. The impact force, structural failure mode and energy dissipation during the collision process are discussed. INTRODUCTION The Norwegian Public Roads Administration is running a "Coastal Highway Route E39" project to replace existing ferry connections by floating bridges or tunnels to cross the fjords in western Norway. Floating bridge concepts have been proposed for the fjord-crossing project for one of the fjords: Bjørnafjorden. One of the challenges in design is to ensure the bridge girder integrity under accidental collisions of drifting ships. Such accidents may occur either during earthquakes or tsunami inundations when ships are drifted or due to the human errors in ship manoeuvring. The collision-induced girder damage can be significant which may consequently lead to the closure or collapse of the whole bridge. Therefore, it is important to evaluate the bridge girder capacity against accidental ship collisions in the design phase. Fig. 1 shows a tanker was pushed by strong winds and rammed into the connecting bridge of Kansai International Airport in Japan in 2018. Severe damage occurred in the ship deckhouse and the bridge girder (Mainichi 2018).

In this study, geometric parameters of a hull such as prismatic coefficient, waterline length, waterplane area coefficient, and flare angle are considered as the main parameters related to the added resistance of ships in waves. The hull form is represented by cross-sectional curves and the free-form deformation (FFD) method is utilized for hull form variation. Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is applied as a multi-objective optimization method to minimize both total resistance and speed loss of a ship in seaways. To estimate these objective functions, the calm water resistance and the added resistance due to winds are calculated by regression formulas, and the added resistance due to waves is predicted by a numerical method based on strip theory, momentum conservation method, and a modified asymptotic formula for the correction in short waves. Moreover, the speed loss is calculated using power-speed curves. It has been shown that the optimization solution with an obvious reduction of total resistance and speed loss in the sea condition of Beaufort 6 can be obtained. INTRODUCTION Recently, there has been a growing interest in operational efficiency and reduction of fuel consumption of ships in accordance with the regulation limiting the emission of greenhouse gases issued by the International Maritime Organization (IMO). Therefore, the shipbuilding industry began to incorporate the operational performance of ships in waves into the early-stage of the ship design. However, the typical ship designs have focused on optimizing only calm water resistance, so it is necessary to carry out multi-objective optimization of hull form considering environmental loads in actual seaways. There have been numerous studies on hull-form optimization considering the resistance of ships. It probably began by Weinblum (1959), and several studies were conducted since the 1970s to minimize calm water resistance in line with the improvement of numerical methods and computing power. Dawson (1977) proposed the modified Rankine source method to solve the wave resistance problem, and in many subsequent studies, the optimization of wave resistance utilizing this method was conducted. In addition, several interesting studies were carried out to optimize the calm water resistance (Nagamatsu et al., 1983; Papanikolaou et al., 1989; Larsson et al., 1992). Recently, studies on hydrodynamic optimization of hull form have been conducted using more sophisticated numerical methods and optimization techniques. Percival et al. (2001) minimized the calm water resistance of Wigley hull for three forward speeds. They distributed the control points over the entire hull and did not apply any constraints so the optimum hull was deformed impractically compared to the basis hull. However, this study was significant as it provided a sophisticated hull-form optimization methodology in terms of resistance. Choi (2015) also conducted a hull-form optimization to minimize the wave-making resistance of a container ship. Deformation was concentrated in the bow part and constraints are applied on displacement and wetted surface area to realize practical hull form variation. More recently, operational efficiency in waves is furthermore considered on hull-form optimization. Bolbot & Papanikolaou (2016) optimized the operational efficiency factors such as added resistance in waves and EEDI factor as the objective function. Yu et al. (2017) optimized both the wave-making resistance and the added resistance at wavelength ratio 0.5 of a 66,000 DWT bulk carrier by modifying a sectional area curve and section shape of the design load waterline. In the study from Jung & Kim (2018), the main dimensions of KVLCC2 tanker were modified and optimization was performed based on the total resistance and the speed reduction considering representative sea conditions. These recent studies have applied multi-objective optimization schemes because of the addition of optimization factors related to operational performance, and most of the hull deformations have been concentrated on the bow part, based on studies in which the front of the hull predominantly contributes to the added resistance in waves (Guo and Steen, 2011; Seo et al., 2013).

Effects of the seawater pressure and density change with the depth on the motion of underwater glider have been conducted in the present research. The net buoyancy that drives the underwater glider accounts for about 0.5 % of the displacement. Because of the lack of controllable actuators, small change of the net buoyancy might have great influences on the steady motion of underwater glider. Taken the seagull underwater glider as a prototype, a new pressure hull of a glider with an operation depth of 2000m has been redesigned. Then, the relationship between the net buoyancy of the glider and the gliding depth was established based on the statistical data of the hydrological parameters of the South China Sea and the deformation of the pressure hull calculated by FEM. The next step is to calculate the influence of the net buoyancy change on the motion of the glider under equilibrium state. Numerical calculation results show that the gliding depth has a great influence on the motion of the glider; the design of net buoyancy system should be treated carefully with consideration of the water pressure and the salinity change to ensure that the glider has the ability to dive to a desired depth. The present investigation proposed a useful insight into the gliding motion of the deep-sea glider, and conclusions could be adopted in the novel buoyancy system of the deep-sea glider. INTRODUCTION Recent years, underwater glider becomes a powerful and cost-effective autonomous sensing platform of oceanographic observation and environment monitoring to collect the column data profiles because of the advantages of low power consumption, easy operability, wide coverage (thousands of km) and long endurance (weeks to months) (Shen, Wang, Yang, Liang & Li, 2018; Kang, Jeoung, Oh, Choi, Kim, Yu, and Cho, 2018). Driven by the net buoyancy, underwater glider glides up and down the ocean column while collecting the physical, chemical, biological, and acoustic data depending on the fitted sensors. Now, some outstanding gliders, such as Slocum (Cooney, 2016; Eichhorn, 2009), seaglider (Yu, Bosse, Fer, Orvik, Bruvik, Hessevik&Kvalsund, 2017; Eriksen, Osse, Light, Wen, Lehman, et al2001), Spray (Rudnick, Sherman & Wu, 2018; Rudnick, Davis, & Sherman, 2016), PETREL (Xue, Wu, Wang, & Wang, 2018), seawing (Yu, Zhang, Jin, Chen, Tian, & Liu, 2011), XRay (D'Spain, Jenkins, Zimmerman, Luby&Thode, 2005) have been developed and applied in the various fields since the concept was proposed in 1989 (Stommel, 1989). Now, the technologies of underwater glider is still development widely, and a variety of new types glider are developed, such as smartfloat (Cao, Lu, Li, Zeng, Yao & Lian, 2019), hybrid-driven glider (Wang, Wei & Zhang, 2018), wave glider (Wang, Li, Liao, Pan & Zhang, 2019), bionic underwater glider (Wu, Yu, Yuan & Tan, 2016).

Reel-laying rigid pipelines induce cyclic deformation that affect the section. Among other, excessive ovality may jeopardize pipe strength during installation & in-service. Previous works shown that conventional material stress-strain relation is no longer suitable for pipeline reel-lay simulations. This paper introduces an advanced model for material behaviour. The evolution of the material behavior and its variations on the cyclic loads paths is detailed. The model uses stressstrain relations and yield surface evolution from the first load curve, with Lüders plateau leading to stabilized cycle with material property variations in cycles. The model has been implemented in finite element software. This model calibration and validation are discussed in this paper. Simulation accuracy is improved compared to published results. INTRODUCTION The pipeline reeling installation process can be a cost-effective installation method for infield flowlines/risers and smaller diameter export lines under certain economical, logistical and technical circumstances. Saipem has acquired a recent pipeline construction vessel, Constellation, which has been designed as a high-performance construction and lay vessel, capable of performing in the world's hardest environments and designed to meet the requirements of current deep and ultra-deep-water projects. During offshore reeling installation, and possibly later pipeline recovery and re-reeling installation, the pipe is reeled, unreeled and straightened. During the process, part of the pipe cross-section has experienced varying levels of plastic deformation in compression and tension, in a cyclic manner. Throughout these steps, the plasticity deformation has modified the pipe material properties, while the other part remains in the elastic domain. Materials under cyclic loading can harden both kinematically and isotropically (or anisotropically). For applications where cyclic loads stay within a single cycle, hardening process comes mainly from kinematic hardening while yield domain surface evolution is negligible. Within a single cycle, Bauschinger effect drive the model behavior, while variation of this behavior through cycles comes from isotropic hardening. The Bauschinger effect refers to a property of materials where the material's stress/strain characteristics change as a result of the microscopic stress distribution of the material. An increase in tensile yield strength occurs at the expense of compressive yield strength. After increasing the tensile yield strength, the local initial compressive yield strength is actually reduced. The greater the tensile strengthening, the lower the compressive yield strength.

SPH-FEM conversion algorithm is proposed to simulate sloping structure and level ice interaction. This method combines the advantages of Finite Element Method (FEM) and Smoothed Particle Hydrodynamics (SPH), which provides a new idea for the research of ice engineering. In this paper, we used this method to simulate the interaction of sloping structure and level ice. Compared with the theoretical result by Croasdale 3D theory, this method predicted the icebreaking force correctly. Simultaneously, it accurately simulated the accumulation process of ice rubbles as the failure finite elements were replaced by SPH particles. Thus, the SPH-FEM conversion algorithm is considered an effective way and will be used in the numerical simulations of ice structures or icebreakers. INTRODUCTION The operation of ships or offshore platforms in the Arctic is often in hash environments, which mainly includes strong wind, high wave, sea ice, low temperature, icing and so on (Bridges et al., 2018; Dehghani-Sanij et al., 2017; Necci et al., 2019). Among them, the ice load on structures is the dominant environmental stress (Xu et al., 2015) and it can cause damage to offshore structures with serious consequences. For example, Vallinsgrunden lighthouse collapsed under several significant ice actions in 1979 (Bjerkås, 2007). Thus, some solutions were proposed to reduce or withstand ice load. Sloping structures are widely found in marine structures to reduce ice loads, such as wind turbines and bridge piers (Barker et al., 2005; Brown et al., 2010) because these reduce bending failure of ice and are likely to be exposed to a severe dynamic ice load (Matskevitch, 2002). Depending on the conditions, the interaction between sloping structure and ice may produce several phenomena. For example, the breaking ice will move up the cone and then clear around the structure in the case of a narrow sloping structure. As for a wide one, rubble accumulation may form in front of the structure (Paavilainen, 2011).

ABSTRACT In the field of aquaculture, gravity cages of various shapes and sizes are used. However, it may be difficult for farm designers to select the size and shape of the cage to be installed. In this study, resistance and dynamic behavior of a cage were investigated numerically in terms of currents and waves; a cage with an internal volume of 8000 m 3 was installed and divided into two, four, and eight cages. The three types of cage systems are described mathematically using a mass-spring model, and effects of the currents and waves were computed in the time domain. The numerical calculation results indicate that the resistance increased with flow rate in all cages, and internal volume reduction rate increased as well. Further, as the number of cages increased for all flow rates, total resistance increased. INTRODUCTION Recently, the importance of cage culture has piqued the interest of many researchers worldwide, and hence the transition from capture fisheries to culture fisheries. The cages used in fish culture are of various shapes and sizes. Whether a cage for aquaculture is on the coast, inland, or offshore, it is difficult for a farmer to choose a cage in terms of shape and size. Given the total volume of a cage, the number of cages to be divided must be determined appropriately. When the total production scale of the farm is determined, the total cage volume can be estimated considering the density of fish determined according to their species. The next question is how to determine the volume of one cage by dividing the total volume. This involves many cases. In this process, the biological characteristics of the species to be bred should also be considered along with the engineering and cost aspects including installation and maintenance. Studies on cages have been performed by analyzing the deformation of the shape of a cage lying in the fluid flow and analyzing the change in the internal volume and tension of the mooring line according to the waves and currents. (Huang et al., 2006, 2007; Lee et al., 2008a, 2015; Li et al., 2006, 2007, 2013). However, few cases have been reported where a cage composed of several cages is regarded as one system, and many cages are analyzed in terms of the overall system efficiency.