Calculation procedure for design structural loads on large berth-connected ships

Object and purpose of research. This paper discusses large berth-connected ships. The purpose of this study was to develop a calculation procedure for design structural loads on the ships of this class. Materials and methods. Probabilistically determined model of ice load calculation for ice-compression scenario. Statistical data on thermal and ice regimes. Main results. Assessment procedure for local ice compression loads on berth-connected ships based on the probabilistically determined model intended for introduction to Russian Maritime Register of Shipping (RS) rules for classification and con-struction of sea-going ships. Conclusion. This paper presents the procedure and main provisions of ice load assignment concept for berth-connected ships, used to develop the draft of RS Rules for ice strength of large berth-connected ships.

Dynamic Response of Jacket-Support Offshore Wind Turbine Under Ice Crushing Load

Offshore wind is one of the fastest developing renewable energy in the world. With increasing exploratory activities in the polar area, wind energy in the cold climate attracts more and more attention. This paper presents an integrated analysis of the ice-structure interaction of a jacket-type offshore wind turbine (OWT). An aero-hydro-servo-elastic jacket wind turbine is created in FAST, which is a well-known tool for wind turbine simulation. Due to vertically sided jacket legs, crushing ice-structure interaction modes are calculated based on the methodology suggested by ISO 19906. Time-domain calculations are carried out for random crushing, intermittent crushing and lock-in crushing between the bottom fixed wind turbine and moving ice feature. Influential parameters like ice thickness, ice strength, ice moving direction and velocity are all studied in this paper. Results show that the ice load has a significant impact on the structure response. The more ice thickness and ice strength will induce the higher structure response mean level, as well as the oscillation amplitudes in all the investigated crushing modes.

Monitoring of the physical and mechanical state of sea ice and short-term prediction of extreme ice phenomena

The article presents the results of studies that complement each other. New methods of instrumental studies of the physical and mechanical characteristics of ice and ice cover are considered.There is briefly described the complex system to developed in the AARI (Arctic and Antarctic research Institute) to determine the strength characteristics of ice formations in natural conditions. The results of determining the ice strength in wells (local strength) at the research station of AARI “Ice Base Cape of Baranov” are presented. The coefficient of comparison of local strength and strength of samples under uniaxial compression is obtained. This allows to determine the ice strength without sampling and testing of samples. On a large experimental material, linear and quadratic approximations for local ice strength were obtained. The influence of the indenter penetration rate on the local ice strength is studied.There is considered the application of the contact remote method for monitoring the dynamic state of the ice cover in order to obtain new data for creating a method of predicting the phenomena of compression and destruction of sea ice in real time.To study the large-scale mechanics of ice during dynamic processes in the air — ice — water system, a modular-block system for ice cover monitoring was developed. The layout of the system was tested in Arctic expeditions.The developed complex system for determining the strength characteristics of ice formations in natural conditions and the modular-block system for monitoring the state of the ice cover complement each other, suggest their further development and improvement, provide wide opportunities for ice research.

On the calculation of normalized viscous–plastic sea ice stresses

Calculating and plotting the normalized states of stress for viscous–plastic sea ice models is a common diagnostic for evaluating the numerical convergence and the physical consistency of a numerical solution. Researchers, however, usually do not explain how they calculate the normalized stresses. Here, we argue that care must be taken when calculating and plotting the normalized states of stress. A physically consistent and numerically converged solution should exhibit normalized stresses that are inside (viscous) or on (plastic) the normalized yield curve. To do so, two possible mistakes need to be avoided. First, when using an implicit solver, normalized stresses should be computed from viscous coefficients and replacement pressure calculated using the previous numerical iterate and the strain rates at the numerator calculated from the latest iterate. Calculating the stresses only from the latest iterate falsely indicates that the solution has numerically converged. Second, for both implicit and explicit (i.e., the EVP) solvers, the stresses should be normalized by the ice strength and not by the replacement pressure. Using the latter, normalized states of stress only lie on the yield curve (i.e., falsely indicating there are no viscous states of stress).

A method for construction of an energy-efficient ice floating pier in the Arctic using hardened ice

This paper presents studies on increasing the ice strength using various additives. It is indicated that addition of wood fiber (artificial composition) and vegetable fiber (natural composition - frozen peat) to ice is an energy-efficient method to increase its strength. This enhances the possibilities of using ice during building and construction works in the Arctic. As an example, the authors proposed a floating ice pier design.

Toward Optimization of Rheology in Sea Ice Models through Data Assimilation

Sea ice models that allow for deformation are primarily based on rheological formulations originally developed in the 1970s. In both the original viscoplastic (VP) and elastic-VP schemes, the internal pressure term is modeled as a function of variable sea ice thickness and concentration with spatially and temporally constant empirical parameters for ice strength. This work considers a spatially variable extension of the rheology parameters as well as wind stress in a one-dimensional VP sea ice data assimilation system. In regions of total ice cover, experiments that assimilate synthetic ice-state observations using variable rheological parameters show larger improvements than equivalent experiments using homogeneous parameters. For partially ice-covered regions where internal ice stresses are relatively unimportant, experiments assimilating synthetic sea ice velocity observations demonstrate reasonable reconstruction of spatially variable wind stresses. These results suggest practical benefits for sea ice–state reconstruction and forecasts by using sea ice velocity, thickness, and concentration observations to optimize spatially varying rheological parameters and to improve wind stress forcing.

On the calculation of normalized viscous-plastic sea ice stresses

Calculating and plotting the normalized states of stress for viscous-plastic sea ice models is a common diagnostic for evaluating the numerical convergence and the physical consistency of a numerical solution. Researchers, however, usually do not explain how they calculate the normalized stresses. Here, we argue that care must be taken when calculating and plotting the normalized states of stress. A physically consistent and numerically converged solution should exhibit normalized stresses that are inside (viscous) or on (plastic) the yield curve. To do so, two possible mistakes need to be avoided. First, to assess the numerical convergence of a solution, one must compute the viscous coefficients and replacement pressure from the previous numerical iterate and the remaining strain rates from the latest iterate. Calculating the stresses only from the latest iterate falsely indicates that the solution has numerically converged. Second, the stresses should be normalized by the ice strength and not by the replacement pressure. Using the latter, one obtains converged states of stress that lie only on the yield curve (i.e., falsely indicating there are no viscous states of stress).

The material properties of ice bridges in the Maxwell Elasto-Brittle rheology

The shape and break-up of landfast ice arches in narrow channels depend on the material properties of the sea-ice. The effect of the material parameters on ice arches in a sea ice model with the Maxwell Elasto-Brittle (MEB) rheology is investigated. The MEB rheology, which includes a damage parameterization, is implemented using the numerical framework of a Viscous-Plastic model. This configuration allows to study their different physics independently of their numerical implementation. Idealized ice bridge simulations show that the elastic part of the model together with the damage parameterization allows the propagation of fractures in space at very short time-scales. The fractures orientation is sensitive to the chosen angle of internal friction, but deviates from theory. It is speculated that these deviations stem from the absence of a flow rule in the rheology. Downwind of a channel, the MEB model easily forms ice arches and sustains an ice bridge. Using a material cohesion in the range of 15–21 kPa is most consistent with the ice bridges commonly observed in the Arctic. Upstream of the channel, the formation of ice arches is complicated by the absence of a relationship between the ice strength and the ice conditions, and by the presence of numerical errors associated with the damage parameterization. Results suggest that the formation of ice arches upwind of a channel is highly dependent on the rheology and calls for more analysis to determine the necessary conditions for their formation.