The formation of a brash ice channel results from frequent ship navigation along fairways or in ports. The formation of brash ice evolves over the winter and is due to the ‘freezing - breaking’ cycle induced by sub-zero temperatures and the ship traffic. Very few studies have been made to evaluate or model the evolution of the channel profile over the winter. The following outlines the analysis of full scale data and model scale brash ice channel measurements. A simple geometric model is developed based on environmental parameters and ship characteristics, namely Cumulative Freezing Degree Days and the vessel beam. The model provides a scheme that can be integrated into brash ice growth models for conceptual designs and marine operations. 1. BRASH ICE CHANNEL DIMENSIONS In the beginning of winter when ice pieces are small and there is not many of them, the brash ice does not cover the whole channel. However, as the winter proceeds, more ice is formed and eventually the whole channel is covered in brash ice. The freeze-breaking cycle from each ship passage determines the growth rate and formation of the channel profile, see Ettema and Huang (1990). As a ship navigates along a channel the brash ice pieces are pushed outwards to the sides and under the intact level ice, whilst some are submerged or washed astern into the centre of the channel. The brash ice pieces then return to an equilibrium state once the ship has passed, with the brash ice moving inwards to the centre of the track. This repeated process of pushing the brash ice to the sides creates a distinctive channel formation, typically considered to be in the shape of a ‘w’, for example as described in the Baltic ship navigation standard TraFi (2011). In this case the profile shape can be characterised by a series of parameters such as the centreline thickness, maximum brash ice thickness (at channel edges), level ice thickness, and the corresponding lateral position of these parameters. The scheme of the 2D geometric navigation channel is shown below in Figure 1. In this study we analyse channel datasets from full scale and model tests to determine the evolution of these parameters over the winter.

Marine oil spill volume and pollution assessment are very important to risk assessment, emergency disposal, accident damage compensation, etc. At present, there is still great controversy on the accuracy and reliability of the marine oil spill volume and pollution assessment. Therefore, this paper proposes a comprehensive multi-technology method for oil spill volume and pollution assessment. Oil spill volume assessment is applicable to various types of oil spill accidents based on the behavior and destination of the oil spill in the marine environment, taking into account the residual oil on the sea surface, weathered oil and recovered and disposed oil; Oil spill pollution assessment, considering the pollution of oil spill to seawater quality, marine sediments, marine organisms and shores, adopts on-site investigation, bio toxicity test, on-site detection technology and numerical simulation technology to evaluate respectively. INTRODUCTION In recent years, marine oil spill and pollution accidents have occurred frequently. Experts both at home and abroad have put great efforts into the oil spill assessment and the methods put forwards has been applied in several large spill assessment (Reddy, 2002; Lehr, 2002; Short, 2004; Leirvik, 2010 ). However, the accuracy and reliability of the assessment of marine oil spill and pollution are still controversial, especially for legal proceedings and damage compensation. This is extremely incompatible with the increasing demand for oil spill and pollution damage assessment. Therefore, it is necessary to carry out research on assessment technology for marine oil spill volume and pollution. Assessment technology for marine oil spill volume and pollution can play a role in various stages of marine environmental risk analysis and assessment, accident emergency disposal and accident damage assessment. In the stage of environmental risk analysis and evaluation, corresponding environmental risk prevention countermeasures and measures are adopted based on the data of marine oil spill volume and pollution assessment; In the emergency disposal of accidents, timely acquisition of oil spill volume and pollution assessment data can provide basis for on-site scientific decision-making of disposal; In postaccident assessment, oil spill volume and pollution are important indicators for evaluating the threat degree of marine oil spill accidents and determining the grade of oil spill accidents, and are also important basis for compensation and accountability for pollution.

The article describes the regional characteristics of the distribution of morphometric parameters of ice ridges in five local areas in the Kara and Laptev Seas. The article gives the main parameters of the morphometry of ice ridges of different water areas. The features of the consolidated layer distribution are shown depending on the study region and the ridge-building conditions. Averaged profiles of the cross-section of the ice ridge are shown, the nature of the change in the thickness of the consolidated layer concerning the sail and keel of the ice ridge is shown. Averaged vertical distributions of porosity are obtained. The article reveals regional differences and general patterns of distributions of the main morphometric characteristics of ice ridges. INTRODUCTION Information about the morphometric characteristics of ice ridges and the patterns of their distribution are necessary to assess the possible ice load in the design of offshore structures (Alekseev et al., 2001). Fig. 1 presents a diagram of an ice ridge. In different regions, the values of the morphometric characteristics of the ice ridges are different, which is mainly due to differences in meteorological and ice conditions. Large-scale studies of AARI and Rosneft in 2013-2017 in the seas of the Russian Arctic have provided a large amount of information about the morphometry of large ice features. This article is a follow-up to "Morphometry and Internal Structure of Ice Ridges in the Kara and Laptev Seas" (Guzenko et al, 2019) with an emphasis on regional features of the distribution of morphometric characteristics. We carried out a comparative analysis of the main parameters of the internal structure of 104 first-year ice ridges studied in 2014-2017 in five local areas: southwest and northeast of the Kara Sea, southwest, northeast and Khatanga Bay of the Laptev Sea (Fig. 2). For the first four areas, the research data from 2014 and 2015 were used, for the Khatanga Bay - research data from 2017. Earlier, AARI conducted already research of first-year ice ridges in the Baydaratskaya Bay of the Kara Sea in 2007 and 2010. The results of these studies are presented in (Mironov and Porubaev, 2011).

The article describes a complex approach to the study of ice ridges and stamukhi, including methods: water thermal drilling, total station and sonar surveys, video filming with help of a submersible vehicle, determining the physical and strength properties of ice. The result of this study is the assessment of the morphometric, strength and age-related properties of the ice feature, as shown by the example of the old composite ice ridge of the East Siberian Sea. INTRODUCTION Ice ridges and stamukhi are large ice features that have a significant mass and are typical of freezing water areas. To determine the possible ice load on marine objects, it is necessary to know the morphometric and physical strength characteristics of ice features. To obtain all necessary characteristics, it is advisable to use several methods. During the joint expeditions of the AARI and Rosneft Oil Company in 2013-2017, more than 150 ice features were investigated in the seas of the Russian Arctic. In most cases, a set of methods was used, including determination of the morphometry and internal structure of ice features using water thermal drilling, total station survey of the surface, sonar and video of the underwater surface of the ice feature, determination of the local ice strength using a borehole jack, taking ice samples to determine the physical (temperature, salinity, density) and strength (compressive and bending strength) properties of ice. The purpose of this article is to demonstrate a comprehensive study of the morphometry and physical-strength properties of ice feature using the example of an old composite ice ridge, to discuss the results, as well as a comparative analysis of the morphometric characteristics of a composite ice ridge with similar parameters of first-year ridges studied during the same period in the same region. On May 9, 2015, as a result of the landing from the Atomic icebreaker "Yamal" on drifting ice north of Bennett Island in the East Siberian Sea, an investigation of the old ice ridge was carried out using various methods. The ice station at which the old ice ridge was studied was located on the ice breccia of first- and second-year ice at a point with coordinates 77°05,1′ N and 149°12,6′ E. During the work, the following hydrometeorological conditions were observed: air temperature −12.1 °C; northeast wind 7 m/s, clear; seawater temperature under ice −1.48 °C; salinity of seawater 26.83 ‰; the depth of the sea is 43 m. The old ice ridge was a complex ice feature, in which two crests could be distinguished (see Fig. 1).

The problem of assessing ice loads and impacts on facilities of developing offshore oil and gas fields has been one of the most relevant in the world in recent decades. When calculating ice loads, the physical and mechanical properties of ice, corresponding to the natural conditions of the region under consideration, should be taken into account. The lack of reliable initial data holds back the pace of design and construction of facilities, which postpones the development of deposits. Currently, there is no unified approach to the selection of standard values for ice cover parameters. Significant differences in the values of design ice loads determined by regulatory methods are due to the manifestation of high spatiotemporal variability of the parameters of the ice regime and the properties of sea ice when interacting with structures, on the one hand, and the imperfection of calculation methods, on the other. The solution to this problem requires the formulation of a wide range of experimental studies of the ice regime in order to determine the most probable range of variability of the functional parameters that determine the magnitude and nature of the loads throughout the ice period, as well as the features of the state of the ice-structure system in a particular physical and geographical area. INTRODUCTION To date, a large number of studies of sea ice have been carried out. These studies can be divided into laboratory and field tests. The former are necessary for studying the mechanics of ice under controlled test conditions. The second ones make it possible to understand more deeply the properties of the ice cover in natural conditions. In the course of such studies (Borodkin, 2016; Johnston, 2001; Johnston, 2002; Johnston, 2006), the processes of changes in some physicomechanical parameters of ice and the process of its degradation were studied. The main drawback of such studies is that many of them were conducted for a limited time in different periods of the ice season - mainly in the spring-summer period. This information does not always reflect the full picture of changes in the properties of ice and, in particular, its strength. Information on the dynamics of changes in the basic design parameters of ice is very important for assessing loads and impacts on structures and its safe operation. Such information is especially relevant for the following purposes:

The critical incidents of the brash ice accumulation are considered using the port of Sabetta as an example. The heat volume, required for the keeping the certain thickness of the brash ice layer is determined using a thermodynamic simulation. The simulation results determine the power capacity of the required heat producing generator. The various methods, that can be used to reduce the energy consumption costs are described, such as: scheduling of the vessels traffic, change of the vessel movement scheme, optimization of the location of the bubbling lines and discharge points of the heated water. INTRODUCTION Currently, active development of the Arctic coast of Russia is under way. Mining companies developed the vigorous activities for development of oil, gas, gas-condensate and other fields. A maritime transport plays an important role in these works. It delivers consumables, machinery and ready-made structures to the Arctic to build the infrastructure. The developed fields begin to supply the raw materials (hydrocarbons and other) to markets by sea. The largest economic activity is observed in the Ob-Yenisei region. It includes the construction of ports and other hydraulic facilities. The port of Dudinka has long operated on the Yenisei River. It provides a transportation of finished products from Norilsk mining and metallurgical plant. The port of Sabetta and the terminal "Arctic Gate" in the Ob' bay had already built for LNG and oil offloading. The design and construction of other facilities, mainly in the northern part of the Ob' bay, continues. The "Utrennyi" terminal is being built on the Gydan Peninsula and it is part of the port of Sabetta. The LNG carrier vessels will be loaded with liquefied natural gas at this terminal. The development of the region is causing a transfer from seasonal sea transportations to year-round traffic. In the Yenisei Gulf, a regular winter sea navigation from the port of Dudinka is carried out since 2008. In the Ob'Bay, a regular winter navigation is carried out from the port of Sabetta since 2013 and from the oil terminal "Arctic Gate" near Kamennyi Cape since 2015. During this time, a sea traffic, for example, in Sabetta, has grown from single calls to several hundred vessels per season.

The Marginal Ice Zone (MIZ) is the transition region between open waters and the sea ice, which has an important effect on ships and offshore structures. A numerical study on the hydroelastic response of ice floes under the action of regular waves in MIZ is presented in this paper. A boundary-element method based on three-dimensional linear potential flow theory is used to predict fluid field. The finite element method is used to numerically model a large ice floe within the framework of the Mindlin plate assumption. A hydroelastic model is formulated using modal superposition method to solve the fluidstructure coupling equations. The hydroelastic response of ice floes under regular waves is studied. The influences of the wavelength and the size of an ice floe on the response are studied and discussed. The results show that the wavelength has a great influence on the displacement of ice floes and the maximum stress in the ice depends on floe size. The ultimate wave height of ice fracture against the ratio of floe length to wavelength is given. The limit wave height of the ice fracture decreases sharply with the length ratio when the floe length is small, and then keeps unchanged for larger floes. INTRODUCTION Studying on interactions between sea ice and waves could help understand global warming, which attracted the attention of the scientific research in recent decades. The research methods on the interactions between ice floes and waves mainly include: experimental method, simplified analytical method and numerical simulation method. Experimentally, Wang et al. (2000) used composite material consisting of polypropylene powder, plastic particles and white cement, to simulate physical characteristics of ice sheets and studied the fracture under the action of waves in a flume, and the relationships between fracture of ice sheets and the ratio of sea floe length to wavelength were obtained. Frankenstein et al. (2001) used 6-DOF instruments to measure the motion of ice floes and inverted the changes in amplitude by the heave amplitude of ice floes. Sakai and Hanai (2002) studied the influence of the sizes and elastic modulus of the ice plate on the incident wavelength. They used a polyethylene material to simulate the ice plate and the results showed that the ice plate had no effect on the speed of wave propagation, when the length of the ice plate was very small. Mcgovern and Bai (2014) studied the relationship between wave characteristics and ice floe motion response by substituting paraffin wax for ice floes. The results showed that wavelength has a great effect on ice floe movement. Dolatshah and Bennets (2018) studied the hydroelastic interaction between regular waves and ice floes under different incident wave periods and steepnesses, and the results showed that the ice sheet would break only if the period and steepness were high enough.

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.

The creation of offshore wind power plants capable of operating in the Arctic marine conditions is a difficult task. Usually, in the Arctic zones, there is no developed industrial infrastructure and there are no skilled workers. In these conditions, it is difficult to build and maintain complex technical devices. Arctic Wind Power Plants should have high reliability in severe operating conditions, use suitable materials for these conditions, installation and assembly technology. This paper contains a review of conceptual design of offshore stationary wind power installations capable of operating in the Arctic conditions. The analysis of available constructional typologies, the evaluation of external loads on these possible options and, finally, the suggestion of approach how to choose installed power capacity of wind turbine which will provide economic expediency of its construction and operation in Arctic marine conditions. INTRODUCTION Centralized energy supply does not exist almost everywhere in Russian Arctic zone. Diesel power plants, which are used now in this area, produce quite expensive electric energy. Besides, the task to provide them with fuel is connected with complex logistic problems. Therefore, it appeals to use offshore wind power plants there, which are delivered and constructed during the summer navigation period. The main parameter, that determines the price of produced energy, is the cost of construction of these wind power plants. It is obvious that the development of offshore wind energy is possible only when arctic offshore wind power plants will have an acceptable cost to compete with other sources of energy. The amount of used metal and the cost of offshore wind power plants depend on the power capacity of installed generator and the external loads, which are affecting the supporting structure and rotor. Structure of offshore wind power installations significantly depends on the sea depth. At relatively shallow depths, stationary structures are usually used. With the increase of sea depth, it becomes more appealing to install wind turbines on a floating base. Conceptual design of floating wind power plants for Arctic zone has been described in previous article written by authors (Bolshev et al., 2019). This paper is dedicated to the various conceptual design options of stationary offshore wind power plants in Arctic zone.

In this paper, submarine models with various rudder profiles are studied and commercial CFD software STAR-CCM+, based on RANS simulations, is carried out to numerically simulate self-propulsion maneuvering motions of the underwater vehicles with different appendages. Finite volume method based on incompressible solver with SST k-ω turbulence model and unstructured grid are applied to study the flow field characteristics. The self-propulsion horizontal turning movement of the SUBOFF models equipped with various rudder profiles are simulated directly to analyze the motion characteristics in each simulation; finally, the impacts of rudder profiles on UV maneuverability are discussed and concluded. INTRODUCTION The maneuverability of the underwater vehicles (UVs) is one of the most important performance in UVs research, and accurately predicting its motion characteristics in maneuvering motion is very necessary for the safety and design. The evaluation of the maneuverability of UVs is traditionally solved by simplified System-Based Models, based on captive model tests or Computational Fluid Dynamics method. Lin (2018) established the Planar Motion Mechanism (PMM) experiments in the towing tank to analyze maneuvering derivatives of a half-scale submerged body DARPA SUBOFF and evaluate the maneuvering derivatives by a Fourier transform. Pan (2012) adopted steady and unsteady RANS simulations and dynamic mesh method to numerically simulate the oblique towing experiment and the PMM experiment performed on the SUBOFF submarine model. Wu (2015) established a hybrid reference frames method that combined the rotating reference frame method and an added momentum source method to investigate the influences of the rotating arm radius and linear velocity in the numerical simulations. With the large progress of the computer technique, people pay more attention to the simulation of the self-propelled test. G. Dubbioso (2017) presented and discussed the results of the free running maneuvering simulations of a fully appended submarine with two different configurations of the stern appendages. Feng (2018) used the volume force method to realize the self-propelled movement of submarine and obtained the trajectory and kinematic parameters. K. Petterson (2018) reported additional simulations of the self-propulsion conditions at ±10 yaw by LES method.

The main factor affecting the operating conditions and the reliability of offshore structures in the production of exploratory drilling in the Russian Arctic is the ice regime of the water area. The problems of exploration drilling in the Arctic are among the most pressing issues in the development of offshore hydrocarbon deposits in the Arctic. The article considers a new approach to assessing the exploration time of offshore drilling rigs in ice conditions and the possibility of their extension in a mode that ensures their normal (safe) operation in such conditions. As an example, the article considers the interaction of ice formations in the form of flat ice fields and their fragments with the legs of the Jack- Up platform, and their geometric parameters (area and thickness) are determined at which the ultimate state of the marine engineering structure does not occur. NOMENCLATURE ODP – offshore drilling platform JUP - Jack-Up platform INTRODUCTION Issues of reconnaissance drilling in water areas with ice regimes remain relevant for economic activities in the Arctic, as traditional drilling platforms such as Jack-Up, Semisubmersible and Drilling Rig, which are widely used in world practice for drilling offshore wells, are wave-resistant, i.e. not designed to work in ice conditions. In this regard, experts are developing new types of ice-resistant offshore drilling platforms to work in difficult ice conditions (For example, Urycheva and Gudmestad, 2014; Toropov, Mokhov, Semenov and Livshits, 2013). One of the most important indicators for assessing the effectiveness of the use of such drilling platforms in the freezing sea is the duration of the navigation period. In the Arctic, the duration of the navigation period is usually insufficient for the construction of one well. Therefore, an urgent problem is the creation of a technology for managing the timing of drilling exploration work in ice conditions based on the management of the geometric parameters of ice formations in the water area using icebreakers. Such technology should include the destruction of drifting ice fields into fragments of controlled sizes and methods for assessing the reliability of a drilling platform depending on the size of ice formations. This technique is applicable to estimating the duration of the drilling season in ice conditions for both existing drilling platforms and newly developed drilling platforms. A description of the methodology for assessing the duration of drilling operations in order to ensure the minimum required drilling time under given ice conditions is given by the example of a Jack-Up platform.

Ice-free period in the southwestern part of the Kara Sea is limited in average to 2-3 months and has significant interannual variability. A preliminary assessment of the ice-free period duration will allow advanced strategic and tactical planning of platforms operating and drilling activities and, thus, costs optimization of exploration drilling. Duration of ice-free period depends on the date of the sea clearing from the ice and on the date of the stable ice formation. Data analysis was based on historical ice maps and satellite information for a 30-year period from 1989 to 2018. Interannual variability of ice free periods, dates of sea clearing from ice and dates of ice formation are considered in the region of geological structures of the southwestern part of the Kara Sea. It is shown that combination of favorable hydrometeorological conditions that in the last decade increased the ice-free period duration by more than a month. Aanalysis of the main hydrometeorological factors determining ice-free period duration showed possibility to estimate the operational window for exploration drilling in the area of geological structures with a lead time of several months. Introduction East Prinovozemelsky license blocks are located in the southwestern part of the Kara Sea between the Novaya Zemlya archipelago in the west, Yamal peninsula in the south and the Taimyr peninsula in the east. The northeastern border of the sea is an imaginary line between the Cape Zhelaniya and the Dickson Island. Several prospective geological structures have been identified within the boundaries of these license blocks (Fig. 1), and in 2014 the Pobeda field was discovered during exploration drilling at the Universitetskaya structure. Usually exploration drilling in freezing seas is carried out in the ice-free period from floating drilling rigs of various ice classes. In the southwestern part of the Kara Sea the ice-free period is limited in average to 2-3 months (Atlas, 2014; Monograph, 2004) and has significant interannual variability.

Brash ice channels are frequently created during ship navigation. To improve the understanding of the brash ice channel development experimental tests have been conducted. The tests were performed by repeated passage of a model ship in a ship channel. Channel profile measurements, temperature profiles, salinity of cores were taken from consolidated brash ice edges and centre of the channel, as well as measurements of the ship model parameters. The results provide insight into the processes in the brash ice channel during freezing and breaking. The paper presents an overview of the tests, measurements and results. The findings from these tests provide an improved understanding of the process in brash ice channel development which can be incorporated into modelling techniques for marine design and operations. 1. INTRODUCTION Brash ice can influence the icebreaking performance of ships and is also created during ice management operations impacting the performance and safety. This is outlined by Riska et al. (1997) and Liferov et al. (2018), amongst others. In this study we consider ‘brash ice’ to be small pieces of ice broken from repeated ship navigation in the same track, see Figure 1. Brash ice accumulations are also present in ports, channels and terminal areas which can impede operations if sufficient amounts are present, as described by Sandkvist (1986). There is, however, a need for understanding of brash ice growth processes for consolidation and thickness prediction. For example, the freezing of the ship channel edges is considered of importance, as these are difficult for icebreakers to break and also in making the channel width narrower. The channel formation is described by Ettema and Huang (1990) and recent brash ice growth models, for example see Riska et al. (2019), include the cyclic ship breaking and refreezing process. The model is based on extension of earlier growth models which modify the Stefan type growth modelling. However these are 1D models and lateral motion of ice is not taken into account. Consequently, an improved physical comprehension is needed on the influence of the development of brash ice channels in order to improve the theoretical modelling of the brash ice processes.

Nuclear power projects have gradually been established in ice zone. Floating ice is one of the potential hazards threatening the safety of cooling water sources of nuclear power projects in winter. In this study, the monitoring items of ice conditions around the first nuclear power plant in ice zone in China were introduced. The analysis results showed that ice cover in the surrounding sea area of the cooling water intakes experienced dramatic changes. The main sea ice risks of cooling water sources were concentrated near the cooling water intakes, but the impact of fast ice and floating ice had less influence on drainage outlets. INTRODUCTION At present, many countries, especially developing countries, need a large amount of power supply and urgently require the development of nuclear energy projects. According to the statistics in the end of 2017, 448 nuclear power units are in operation in 31 countries around the world and the total installed capacity of nuclear power units reaches 400 million kW, accounting for about 10% of the global power generation (World nuclear association, 2018a). The proportion of nuclear power once reached 16%. By July 1, 2017, the numbers of nuclear power units under construction and to be constructed respectively reached 59 and 160 and the total market size of nuclear power was nearly $1.2 trillion (World nuclear association, 2018a). In China, nuclear power is a kind of clean energy of strategic significance for meeting the power demand, optimizing the energy structure, ensuring energy security, and promoting sustainable economic development. It is also an effective way to achieve carbon dioxide emission reduction goals and the coordinated development of energy, economy, and environment. According to the Thirteenth Five-Year Plan for Chinese Electric Power Development, the installed capacity of nuclear power units in China will reach 58 million kW in 2020 and the installed capacity of nuclear power units under construction is over 30 million kW. By November 2017, 37 nuclear power units have been put into commercial operation in mainland China and 19 nuclear power units were under construction. The installed capacity of nuclear power units in China ranks fourth in the world and the number of nuclear power units under construction in China ranks first in the world for many years (World nuclear association, 2018b; World nuclear association, 2018c).

Due to the influence of island type, there are serious wave energy concentration and overtopping. In order to understand influence of wave forces on bridges in island-bridge junctions on structural safety under extreme conditions such as hurricane waves and astronomical tides, selecting the most unfavorable SW and SE waves direction on the bridge and carried out physical model test, and comparing results with canonical formula calculated and measured forces of the completed HongKong-Zhuhai-Macau Bridge. Finally, test purpose was achieved by optimizing elevation. This test also verified the necessity of physical model test in force measurement and optimization design. INTRODUCTION The Shenzhen-Zhongshan channel in this study is a "four in one" cluster project integrating ultra wide and ultra long subsea tunnel, ultra large and cross Sea Bridge, deep-water artificial island and underwater interchange. It has unprecedented scale, extremely complicate construction conditions and new comprehensive technical difficulties. It is another world-class major cross sea traffic project after Hongkong- Zhuhai-Macau Bridge in China. See Fig.1 is the project location and Fig.2 for layout of west artificial island. In the root area of the bridge at the junction of the island and the bridge on the west side of the island, through the preliminary physical model test, it is found that there are complex wave states such as wave energy concentration, vortex flow and so on in this area under the influence of the island type, and the wave overtopping on the top of the crest is the most serious. In addition, limited by the land elevation of the west artificial island, the bottom elevation of the bridge at the junction of the island and the bridge is the lowest, which is easy to be affected by the wave current coupling jacking force and lateral force, thus posing a serious threat to the safety of the bridge structure, and even the risk of damage. For the complex wave conditions, there are some difficulties in the selection of bridge design safety parameters. If the calculation is based on the similar standard formula, the results are often deviated greatly, and even there are some cases where the formula limit conditions are not applicable.

The traditional method to check ultimate strength is deterministic method, which does not consider the influence of uncertain factors. In this paper, a 10,000 TEU container ship is chosen as studying object, whose ultimate strength is calculated by Smith's method. In addition, deterministic optimization is also performed, obtaining an optimization solution. Then, First Order Reliability Method (FORM) is used to analyse its reliability. Particle Swarm Optimization (PSO) is employed to reduce the weight and painting area simultaneously, which is a multi-objective optimization problem. Moreover, the analysis of the influence of different factors on the reliability index is also included. Finally, some conclusions are drawn based on optimized design solutions. INTRODUCTION Safety of ultra large container ship (ULCS) structures has been the main concern of designers. Historically, many scholars had conducted extensive research on longitudinal strength. In order to enrich the theory of hull structural strength and solve practical problems, Vista (1958) first proposed the concept of ultimate strength. Later, Caldwell (1965) took the ultimate strength as the full plastic bending moment of the section, and applied it to the calculation of longitudinal ultimate strength of a practical ship. With more understanding of the hull failure mechanism, Smith (1977) assume that the hull beam failure is a gradual process and proposed a new method for calculating the ultimate strength, which is also called as progressive failure method or Smith's method. Ueda, Rashed & Paik (1984) also proposed the Idealized Structural Unit Method (ISUM) where idealized structural collapse modes are assumed and both geometric and material nonlinearities are included. Nowadays, with the development of computer science and the popularization of finite element commercial software, the application of Nonlinear Finite Element Method (NFEM) to calculate the ultimate strength is also increasingly employed. However, those methods are all deterministic for simplicity and do not consider uncertain factors, but the practical situation the ships encounter are highly uncertain in nature, e.g. uncertainties lie within the external loads as well as structure itself. When deterministic method is used to check ultimate strength, it is considered that once Eq. 1 is satisfied, a certain ship's ultimate strength will meet deterministic requirement. In Eq. 1, M u is ultimate hull bending moment, M is external load, and γ R is partial safety factor. (equation)

ABSTRACT Structure-from-Motion is a technique for estimating 3D structures from 2D image. Due to different refractive index of mediums, the light ray will bend during the underwater imaging process, making the perspective camera model invalid. In this paper we set a camera fixed in a glass housing and use a virtual camera geometry relationship to describe the imaging process, it's analyzed that the relative camera transform between two images can be recovered and the 3D object points can be reconstructed with absolute scale. Under different thickness of refractive plane, synthetic reconstruction experiments are conducted and the result demonstrates good performance of proposed method. INTRODUCTION In many underwater applications, three-dimensional structure of underwater object is needed to gain measurements. One of the significance methods to gain the 3D structure is Structure-from-Motion, which can recover the structure of object from two-dimensional image sequences captured with different camera poses. However, underwater images are often obtained by a camera fixed in a glass housing, thus the light ray coming from water will meet three different mediums: water, glass and air. Due to the different refractive index, refraction occurs. The fact that light ray will bend during imaging makes the perspective camera model invalid for Structure-from-Motion with underwater images. In order to deal with the problem, some try to simplify the model by assuming the glass to be very thin (Treuvutz, Schechner, Kunz and Singh, 2012) or drive the effect caused by refraction into the change of focal length and radial distortion (Lavest, Rives and Lapresté, 2000), some use underwater calibration targets to do reconstruction(Kunz and Singh, 2008; Telem and Filin, 2010) though it's not applicable in real operation. Agrawal et al.(2012) analyzed the geometry of multi-layer refractive system and modeled it with an axial camera, dividing the calibrating process into axial estimation, glass housing thickness estimation and so on. However, the system can be used to estimate pose of the camera on the basis of the 3D-2D correspondences given.

ABSTRACT A new resonance-regulated testing device operating at a frequency of up to 200 Hz has been developed for very high cycle fatigue tests on large-scale cast iron and steel specimens. The device is able to perform tests on axially loaded plate specimens with a thickness of up to 20 mm and a width of up to 40 mm. It allows testing with a maximum amplitude of 70 kN and a stress ratio of 0.1 ≤ R ≤ 0.5. In this paper, the working principle of the device is shown. Furthermore, the calibration, pretension and testing procedures are presented based on the tests with ductile cast iron specimens (EN-GJS-18C-LT). INTRODUCTION Offshore wind turbines are expected to experience up to 10 9 load cycles during their service life (Seidel, 2010). Thus, the fatigue limit state represents a crucial factor during the design process. In current offshore standards and guidelines (DIN 18088–3, 2019; DNVGL-RP-C203, 2016; DNVGL-ST-0361, 2016), the design S-N curves do not allow for an endurance limit. These S-N Curves are mostly derived from fatigue tests up to 10 7 load cycles. The shape of S-N curves for more than 10 7 load cycles and the question of the existence of an endurance limit are still of particular interest of ongoing research (Schaumann and Steppeler, 2013; Steppeler, 2014). The investigation of this range requires testing facilities able to perform a very high number of cycles (beyond 10 7 ) within a reasonable timeframe. Over the last decades, different servo-hydraulic, resonant, forced-vibration, rotating-bending and ultrasonic machines for very high cycle fatigue tests have been developed (Stanzl-Tschegg, 2014). The testing frequency of these machines lies between several hundred Hz in case of servo-hydraulic machines to up to 20 kHz for the ultrasonic testing equipment. One of the main limitations of these machines is that only small-sized specimen can be tested. This yields to a smaller testing volume, which reduces the probability of encountering large defects. Hence, higher fatigue strength can be measured (Furuya, 2010). Considering offshore wind turbines with some structural components whose wall thicknesses exceed 100 mm, it is necessary to perform tests on large-scale specimens to limit possible scale effects. An improved experimental basis of fatigue tests is vital for optimization of these structures.

ABSTRACT The preheating flame gas composition influence during the oxyhydrogen cutting process is examined carrying out spot heating tests. An inverse heat conduction analysis is applied for these test results to determine the local heat transfer parameters influence. To measure the gas composition influence on the piercing performance piercing-tests are carried out. A heat conduction analysis is performed to estimate the minimum piercing time for the selected preheating flame. The accuracy of the estimated piercing time was validated by the actual minimum piercing time during the piercing test. INTRODUCTION During the Oxy-fuel cutting process, a workpiece is heated by a preheating flame until it reaches its kindling temperature, then oxygen is blown in the mixture to start the cutting process. During the process, heat is supplied both by heat transfer from the preheating flame, and through the combustion of the material itself. During the last years, there has been a growing interest in using Hydrogen (H 2 ) for the preheating flame of the oxy-fuel cutting process since the use of H 2 increases the cutting performance, reduces the thermal distortion of the workpiece, and also reduces the Carbon Dioxide (CO 2 ) emission during the process. In practical applications of Oxy-Hydrogen cutting (OHC), the preheating flame is composed of a mixture of gases. Generally, H 2 is mixed with a fossil gas, such as liquefied petroleum gas (LPG), to improve the visibility of the preheating flame since the H 2 flame is almost invisible and hard to adjust. On the other hand, as reported by Taniguchi (2004), by using a fossil gas helps to avoid drastic explosions during the mixture gas ignition, improving the process safety. However, one of the side effects of mixing fossil gases in the preheating flame is the reduction of the cutting efficiency. Several studies have shown deterioration of the cutting performance (e.g. cutting speed, kerf quality, thermal distortion) while adding fossil gases in the preheating flame. In this regard, the precise deterioration mechanism of the process has not been fully clarified yet which leads to multiple preheating gas compositions that always claim the best cutting performance. Another significant issue with the OHC preheating flame is that the flame optimization process is performed manually and usually relies on the individual skill of experienced workers. As a result, there is a considerable incentive to automate the preheating flame adjustment along with the gas composition as much as possible.

ABSTRACT Submarine pipelines are key infrastructures in offshore oil and gas engineering. They are widely used for transportation of the oil and gas from production wells to onshore facilities. With the development of the port engineering and the exploitation of ocean oil and gas resources, overlap may occur between the harbor channel area and the landfall part of submarine pipelines. There is an occurrence that a buried submarine pipeline in a channel is damaged by the collision of falling objects from third party activities, e.g., a falling anchor for a ship. In order to seek reasonable protection measures to ensure the safe operation of the pipeline, it is necessary to analyze the dynamic response of the pipeline caused by the dropped objects. In this study, different protective measures on the pipeline, including pure rock layer, concrete mattress + rock layer, concrete mattress + rock layer + rubber pad and compound flexible pad + rock layer, are physically modelled in the tests to study the impact effect of a dropped anchor on the pipelines. The dynamic responses of the pipeline are measured with a series of Fiber Bragg Grating (FBG) sensor on the surface of the pipeline to analyze its maximum value and the distribution of the strain. The most effective protective measures and its thickness can be determined based on the experiments. The present work can provides the significant support for the design and maintenance of submarine pipelines. INTRODUCTION One of the most significant challenges in operating offshore pipelines is assessing the effects of external damage. When a direct impact on a pipeline occurs, assessment is required to determine whether the pipeline should continue to operate, operate with reduced pressure, or completely shut down the pipeline. Because of the tightness of port shoreline resources, there are often cases that the landing part of a submarine pipeline crosses the channel. If the original grade of the channel is not enough, it needs to be upgraded and reconstructed with excavation to increase the effective depth. This will inevitably affect the safety of the submarine pipeline under the original channel seabed. For example, there being an offshore pipeline crossing the channel of Dongying Port, China, the pipeline is covered by a protective layer of 4.0m thickness of sand filling in the original design of the pipeline. However, with the necessity of upgrading the channel, the water depth of the channel will be increased by 2m after excavation, so that only 2.0m protective thickness of sand filling is left, which is definitely unsafe according to the original design of the pipeline. In order to meet the requirements of pipeline protection after channel dredging, different protective method have to be tested to find a best solution.