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The Arctic presents a great opportunity for two major industries. First, since the region is expected to contain a significant amount of hydrocarbon reserves, it is very attractive for the oil and gas industry. Second, the receding extent of sea ice is making the region more accessible for shipping and, therefore, an opportunity is emerging for the shipping industry. In order to exploit both economic opportunities in a safe and sustainable manner, a thorough understanding of the interaction between ice and floating structures is needed. The most common method for studying ice-floater interaction (IFI) is via numerical modeling, which the fluid is a major component of. As fluid-ice interaction is challenging to model, a wide range of simplified and sophisticated models are employed to meet the challenge. A literature study was performed on the usage of fluid models employed in IFI and it was found that they can be divided into four categories: hydrostatic models, models based on potential flow, models based on Reynolds-averaged Navier–Stokes or a similarly advanced method, and effective fluid models. The hydrostatic models are by far the most prevalent despite only accounting for buoyancy. Most IFI models that account for hydrodynamics make use of potential theory. These models account for fluid flow and surface waves, which together alter the dynamic behavior of floating ice, resulting in hydroelastic effects. The surface-wave-based coupling between ice and floater has not been studied before and there are still open questions regarding the effects of hydroelasticity on the bending failure of ice. The advanced fluid models are a recent trend in IFI and, consequently, most of those are still under development. These models are very promising and may be the future of IFI modeling. Finally, the effective models avoid the practical issues associated with hydrodynamic models in terms of development and calculation time by capturing hydrodynamics in an effective manner, e, Offshore Engineering

Interaction of sea or lake ice with vertically sided offshore structures may result in severe structural vibrations commonly referred to as ice-induced vibrations. With the surge in offshore wind developments in sub-arctic regions this problem has received increased attention over the last decade, whereas traditionally the topic has been mainly associated with lighthouses and structures for hydrocarbon extraction. It is important for the safe design of these offshore structures to have the ability to predict the interaction between ice and structure in an expected scenario. A model for simulation of the interaction between a drifting ice floe and a vertically sided offshore structure is presented. The nonlinear speed dependent ductile and brittle deformation and local crushing of ice are considered phenomenologically. A one-dimensional sea ice dynamics model is applied to incorporate the effects of floe size, wind and current. The structure is modelled by incorporating its modal properties obtained from a general-purpose finite element software package. Alternatively, the model can be coupled to in-house design software for fully coupled simulations. Examples of application of the model to simulate dynamic ice-structure interaction are provided. Simulation results are validated with public data from forced vibration experiments, small-scale intermittent crushing and frequency lock-in, and full-scale interaction with the Norströmsgrund lighthouse. Effects of floe size and environmental driving forces on the development of ice-induced vibrations in full-scale are studied. It is shown that sustained frequency lock-in vibrations of the structure can only develop for very specific combinations of environmental driving forces and ice floe size. In all other cases, the ice floe slows down and comes to a stop, or accelerates to a drift speed which exceeds the range where frequency lock-in develops. This results in only a few cycles of vibration per interaction event, such a, Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Hydraulic Engineering, Offshore Engineering

The Arctic presents a great opportunity for two major industries. First, since the region is expected to contain a significant amount of hydrocarbon reserves, it is very attractive for the oil and gas industry. Second, the receding extent of sea ice is making the region more accessible for shipping and, therefore, an opportunity is emerging for the shipping industry. In order to exploit both economic opportunities in a safe and sustainable manner, a thorough understanding of the interaction between ice and floating structures is needed. The most common method for studying ice-floater interaction (IFI) is via numerical modeling, which the fluid is a major component of. As fluid-ice interaction is challenging to model, a wide range of simplified and sophisticated models are employed to meet the challenge. A literature study was performed on the usage of fluid models employed in IFI and it was found that they can be divided into four categories: hydrostatic models, models based on potential flow, models based on Reynolds-averaged Navier–Stokes or a similarly advanced method, and effective fluid models. The hydrostatic models are by far the most prevalent despite only accounting for buoyancy. Most IFI models that account for hydrodynamics make use of potential theory. These models account for fluid flow and surface waves, which together alter the dynamic behavior of floating ice, resulting in hydroelastic effects. The surface-wave-based coupling between ice and floater has not been studied before and there are still open questions regarding the effects of hydroelasticity on the bending failure of ice. The advanced fluid models are a recent trend in IFI and, consequently, most of those are still under development. These models are very promising and may be the future of IFI modeling. Finally, the effective models avoid the practical issues associated with hydrodynamic models in terms of development and calculation time by capturing hydrodynamics in an effective manner, e, Offshore Engineering

Interaction of sea or lake ice with vertically sided offshore structures may result in severe structural vibrations commonly referred to as ice-induced vibrations. With the surge in offshore wind developments in sub-arctic regions this problem has received increased attention over the last decade, whereas traditionally the topic has been mainly associated with lighthouses and structures for hydrocarbon extraction. It is important for the safe design of these offshore structures to have the ability to predict the interaction between ice and structure in an expected scenario. A model for simulation of the interaction between a drifting ice floe and a vertically sided offshore structure is presented. The nonlinear speed dependent ductile and brittle deformation and local crushing of ice are considered phenomenologically. A one-dimensional sea ice dynamics model is applied to incorporate the effects of floe size, wind and current. The structure is modelled by incorporating its modal properties obtained from a general-purpose finite element software package. Alternatively, the model can be coupled to in-house design software for fully coupled simulations. Examples of application of the model to simulate dynamic ice-structure interaction are provided. Simulation results are validated with public data from forced vibration experiments, small-scale intermittent crushing and frequency lock-in, and full-scale interaction with the Norströmsgrund lighthouse. Effects of floe size and environmental driving forces on the development of ice-induced vibrations in full-scale are studied. It is shown that sustained frequency lock-in vibrations of the structure can only develop for very specific combinations of environmental driving forces and ice floe size. In all other cases, the ice floe slows down and comes to a stop, or accelerates to a drift speed which exceeds the range where frequency lock-in develops. This results in only a few cycles of vibration per interaction event, such a, Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Hydraulic Engineering, Offshore Engineering

Calving is a complex process subject to several cooperating atmospheric, oceanographic and glaciological forcings that vary in space and time, and whose relative effects are challenging to separate. Statistical ‘Systems Analysis’ is commonly used in engineering and economics to extricate complex ‘force–response’ relationships. Here we apply Systems Analysis to the Amery rift system, East Antarctica. We develop a scalable ‘System Model’ driven by a coarsely-sampled dataset characteristic of glaciological observations in remote locations, and validate it using rift lengths observed in 2000–06 and 2012. In this initial demonstration, we forecast a detachment date of ∼2019 ± 5 years for the large tabular iceberg colloquially known as the ‘Loose Tooth’, for which relative humidity surprisingly emerges as the best statistical predictor. RACMO2 climate modelling reveals that relative humidity correlates best with surface albedo and snowmelt, both of which are intimately linked to firn compaction and ice shelf temperature and flow. We postulate that relative humidity can therefore serve as a proxy for internal stress, a known key control of ‘Loose Tooth’ calving. Although no physical causality is implied in Systems Analysis, postulates such as this can aid in setting priorities in studies of complex glaciological processes.

Offshore developments in ice-covered waters, such as the Arctic Ocean or Baltic Sea, have received increasing attention from the petroleum and wind power industries over the past decade. Sustainable developments in such waters can contribute to a balanced energy future provided that the deployed offshore structures are designed to be safe. The potential development of ice-induced vibrations has to be considered in the design of bottom founded offshore structures with a vertically sided waterline cross-section subject to ice. These vibrations, originating from dynamic interaction between the ice and structure, can result in high global peak loads and significantly contribute to the fatigue of structures. A governing theory which can explain the development of ice-induced vibrations has not yet been defined, despite several decades of research. As a consequence the tools required for detailed design of structures subject to ice-induced vibrations are not yet available. The main objective of this study is to define a physical mechanism which can explain the development of ice-induced vibrations and is consistent with existing experimental and full-scale observations. A literature study and new experiments in the large ice-basin at HSVA in Hamburg have resulted in the identification of key features of the interaction process. A new theory has been proposed, namely that the variations in the contact area between the intact ice and structure govern ice-induced vibrations. These variations result from the velocity dependent deformation and failure behaviour of the ice. Based on the theory a phenomenological model for the prediction of ice-induced vibrations has been developed of which the predictions have been shown to be consistent with experimental observations. Additionally, the limiting effect of ice buckling on ice-induced vibrations has been studied and practical application of the model illustrated on the basis of simulation examples., Applied Mechanics

Offshore developments in ice-covered waters, such as the Arctic Ocean or Baltic Sea, have received increasing attention from the petroleum and wind power industries over the past decade. Sustainable developments in such waters can contribute to a balanced energy future provided that the deployed offshore structures are designed to be safe. The potential development of ice-induced vibrations has to be considered in the design of bottom founded offshore structures with a vertically sided waterline cross-section subject to ice. These vibrations, originating from dynamic interaction between the ice and structure, can result in high global peak loads and significantly contribute to the fatigue of structures. A governing theory which can explain the development of ice-induced vibrations has not yet been defined, despite several decades of research. As a consequence the tools required for detailed design of structures subject to ice-induced vibrations are not yet available. The main objective of this study is to define a physical mechanism which can explain the development of ice-induced vibrations and is consistent with existing experimental and full-scale observations. A literature study and new experiments in the large ice-basin at HSVA in Hamburg have resulted in the identification of key features of the interaction process. A new theory has been proposed, namely that the variations in the contact area between the intact ice and structure govern ice-induced vibrations. These variations result from the velocity dependent deformation and failure behaviour of the ice. Based on the theory a phenomenological model for the prediction of ice-induced vibrations has been developed of which the predictions have been shown to be consistent with experimental observations. Additionally, the limiting effect of ice buckling on ice-induced vibrations has been studied and practical application of the model illustrated on the basis of simulation examples., Applied Mechanics

Ice-induced vibrations can occur when flexible, vertically-sided offshore structures are subject to level ice such that the failure mode of ice is predominantly crushing. When the ice is relatively thin, or when the width of the structure is much larger than the ice thickness, the ice tends to buckle and subsequently fail as soon as the stress caused by the buckling exceeds the bending strength of the ice sheet. This type of failure is referred to in this paper as buckling failure. The buckling failure can limit the global load on the structure but not necessarily prevents the development of ice-induced vibrations. Study of the latter in cases when ice fails by mixed crushing and buckling is of interest for the design of offshore structures as well as for the interpretation of model-scale tests which often show buckling as a consequence of the use of relatively thin ice. In this study a phenomenological approach for ice crushing and a model of a wedge beam on elastic foundation are combined, thereby composing a simplified model which incorporates both crushing and flexural motion of the ice sheet. Typical load signals and a failure mode map generated with the model correspond well with model-scale observations in a qualitative sense. The model predicts that ice-induced vibrations of limited duration can develop as long as the buckling failure does not occur within at least one period of intermittent crushing or frequency lock-in. A specific case is discussed for which buckling failure would be expected to occur, but sustained intermittent crushing is observed instead, illustrating that buckling does not necessarily limit the development and duration of ice-induced vibrations, but even the opposite could happen. The possibility for ice-induced vibrations to develop in the regime of mixed crushing and buckling failure is further discussed focusing on the effects of the boundary conditions, structural shape and structural and ice properties., Applied Mechanics, Offshore Engineering

Ice-induced vibrations can occur when flexible, vertically-sided offshore structures are subject to level ice such that the failure mode of ice is predominantly crushing. When the ice is relatively thin, or when the width of the structure is much larger than the ice thickness, the ice tends to buckle and subsequently fail as soon as the stress caused by the buckling exceeds the bending strength of the ice sheet. This type of failure is referred to in this paper as buckling failure. The buckling failure can limit the global load on the structure but not necessarily prevents the development of ice-induced vibrations. Study of the latter in cases when ice fails by mixed crushing and buckling is of interest for the design of offshore structures as well as for the interpretation of model-scale tests which often show buckling as a consequence of the use of relatively thin ice. In this study a phenomenological approach for ice crushing and a model of a wedge beam on elastic foundation are combined, thereby composing a simplified model which incorporates both crushing and flexural motion of the ice sheet. Typical load signals and a failure mode map generated with the model correspond well with model-scale observations in a qualitative sense. The model predicts that ice-induced vibrations of limited duration can develop as long as the buckling failure does not occur within at least one period of intermittent crushing or frequency lock-in. A specific case is discussed for which buckling failure would be expected to occur, but sustained intermittent crushing is observed instead, illustrating that buckling does not necessarily limit the development and duration of ice-induced vibrations, but even the opposite could happen. The possibility for ice-induced vibrations to develop in the regime of mixed crushing and buckling failure is further discussed focusing on the effects of the boundary conditions, structural shape and structural and ice properties., Applied Mechanics, Offshore Engineering

The objective of this study was to contribute to the knowledge on ice-ridges structures interactions. This work is a follow-up of previous research on simulations of ice-structure interaction using finite element method (Gürtner, 2009b; Konuk, et al., 2009a,b) and a preliminary study of freeze-bond (FB) shear strength (Repetto-Llamazares, et al., 2009b). The presented data should be regarded as illustrative rather than exhaustive. Many important aspects of ice-ridges structures interactions have not been addressed in this thesis. An analysis of experiments with FBs was performed, and a finite element model was built in order to simulate these experiments. Within the framework of the classical theory of elasticity, the numerical model incorporates a cohesive model in order to simulate ice fracture along the FB during shear test. The cohesive behavior of the FB was described by the bilinear traction-separation law. The approach of Camanho and Davila (2002) was applied in order to calculate stresses in the FB under mixed-mode loading conditions. A 6-node cohesive finite element was used for implementation of assumed behavior of the FB. Information obtained via detailed analysis of the FB shear strength experiments and via their numerical simulation can be used for a better understanding of FB failure processes and for a numerical modeling of ice-ridges. The results of numerical simulation confirmed that the finite element model could reproduce phenomena commonly observed in actual shear tests of FBs, including the shear strength hardening and partly softening behavior. The peak load in simulations was completely determined by the maximum traction strength and the initial part of a traction-separation law. This study also showed that from the conducted experiments intended to study FB strength in model ice, it is also possible to study ice fracture processes as well as post-failure behavior. By improving the experimental procedure as described in Repetto-Llamazares, et, CoMEM - Coastal and Marine Engineering and Management, Hydraulic Engineering, Civil Engineering and Geosciences

The objective of this study was to contribute to the knowledge on ice-ridges structures interactions. This work is a follow-up of previous research on simulations of ice-structure interaction using finite element method (Gürtner, 2009b; Konuk, et al., 2009a,b) and a preliminary study of freeze-bond (FB) shear strength (Repetto-Llamazares, et al., 2009b). The presented data should be regarded as illustrative rather than exhaustive. Many important aspects of ice-ridges structures interactions have not been addressed in this thesis. An analysis of experiments with FBs was performed, and a finite element model was built in order to simulate these experiments. Within the framework of the classical theory of elasticity, the numerical model incorporates a cohesive model in order to simulate ice fracture along the FB during shear test. The cohesive behavior of the FB was described by the bilinear traction-separation law. The approach of Camanho and Davila (2002) was applied in order to calculate stresses in the FB under mixed-mode loading conditions. A 6-node cohesive finite element was used for implementation of assumed behavior of the FB. Information obtained via detailed analysis of the FB shear strength experiments and via their numerical simulation can be used for a better understanding of FB failure processes and for a numerical modeling of ice-ridges. The results of numerical simulation confirmed that the finite element model could reproduce phenomena commonly observed in actual shear tests of FBs, including the shear strength hardening and partly softening behavior. The peak load in simulations was completely determined by the maximum traction strength and the initial part of a traction-separation law. This study also showed that from the conducted experiments intended to study FB strength in model ice, it is also possible to study ice fracture processes as well as post-failure behavior. By improving the experimental procedure as described in Repetto-Llamazares, et, CoMEM - Coastal and Marine Engineering and Management, Hydraulic Engineering, Civil Engineering and Geosciences

Overzicht van kunstmatige eilanden t.b.v. de oliewinning in arctische gebieden (rond de Noordpool, Beaufort Sea). Includes a risk analysis for such an island, Hydraulic Engineering, Civil Engineering and Geosciences

Overzicht van kunstmatige eilanden t.b.v. de oliewinning in arctische gebieden (rond de Noordpool, Beaufort Sea). Includes a risk analysis for such an island, Hydraulic Engineering, Civil Engineering and Geosciences

This work reviews two models of ice sheet interaction with a particular structural shape, an isolated circular pile. A new model is developed using classical small element elastic theory. The ensuing equations are reduced by an adaptation of circular symmetry from a plane stress, two-dimensional representations to an infinite number of one-dimensional representations. The equations are then solved numerically by a finite difference technique and a finite number of solutions are recombined into an approximation of the true solution. The model is extended to a viscoelastic formulation with the Maxwell model. Some results and conclusions concerning areas of potential material failure and frictional effects are drawn. The computer code used is included and suggestions for further improvements are noted. (Author)

The most efficient design, construction, and use of polar-ice-shelf facilities for operation and parking of aircraft, cargo storage, and other purposes depends on a thorough and correct engineering analysis of the structural integrity of the sea-ice layer. The viscoelastic finite element analysis technique and computer program developed in this investigation have proven to be an accurate, versatile, and powerful tool for solving a wide class of boundary value problems including ar-bitrary axisymmetric and plane strain geometries subjected to quasi-static, symmetric loading, and layered half-space systems resting on a fluid foundation with arbitrary surface loading. The viscoelastic model includes independent bulk and shear relaxation functions charac-terized by exponential series. The computer program was exercised on several sample problems and compares favorably with classical solutions and experimental data. (Author, modified-PL)

Norman Hells is situated on the north bank of the Mackenzie River, 145 km south of the Arctic Circle. The use of a pool-wide water flood system for secondary recovery and the features of the oil-bearing structure require six man-made platforms to provide vertical access to the portion of the oil pool that 1 ies beneath the Mackenzie River (60%). With a view to the economic viability of the secondary recovery project, man-made islands - hydraulically filled - represent the least risk of massive failure in connection with the environmental loads to be expected. As the man-made islands predominantly determine the economic feasibility of the expansion project, their design has been kept conservative, reflecting a tried and true construction concept, appl ied under various conditions. The design criteria were established by Esso Resources Canada Ltd. in co-operation with Hydronamic. The 'final' design resulted from several additional studies and computations. This report embraces the results of the above-mentioned studies and computations in hydraul ic engineering focussing on: (1) the computation of surge velocities during the release -of severe river-ice jams; (2) the computation of the degree of damage to the rip-rap slope protection; (3) the prediction of the development of local scour in the river bed adjacent to the rip-rap apron.

Norman Hells is situated on the north bank of the Mackenzie River, 145 km south of the Arctic Circle. The use of a pool-wide water flood system for secondary recovery and the features of the oil-bearing structure require six man-made platforms to provide vertical access to the portion of the oil pool that 1 ies beneath the Mackenzie River (60%). With a view to the economic viability of the secondary recovery project, man-made islands - hydraulically filled - represent the least risk of massive failure in connection with the environmental loads to be expected. As the man-made islands predominantly determine the economic feasibility of the expansion project, their design has been kept conservative, reflecting a tried and true construction concept, appl ied under various conditions. The design criteria were established by Esso Resources Canada Ltd. in co-operation with Hydronamic. The 'final' design resulted from several additional studies and computations. This report embraces the results of the above-mentioned studies and computations in hydraul ic engineering focussing on: (1) the computation of surge velocities during the release -of severe river-ice jams; (2) the computation of the degree of damage to the rip-rap slope protection; (3) the prediction of the development of local scour in the river bed adjacent to the rip-rap apron.

Increasing operational use of ice areas in polar regions has intensified the need for improved knowledge, techniques, and procedures for utilization of polar ice in shore-based activities and floating platforms. A linear equation relating flexural strength (rupture modulus) with brine volume was developed for temperature range -2C to -10C for normal seawater ice. The analysis included data from large field-tested beams and small laboratory-tested beams. The stress-strain relationship for the small laboratory beams tested for temperature range -4C to -10C under elastic loading condition was found to be linear, while the elastic modulus was observed to behave as a nonlinear function of temperature. Limited sampling indicates secondary creep is related to stress and can be expressed as a material constant multiplied by stress to an exponential power; both stress and creep are temperature sensitive. In contrast to the results of previous studies, the basal plane of the polycrystalline specimens of saline ice was not observed to be the weakest shear plane. (Author)

Tensile strength envelopes were developed for horizontally and vertically oriented specimens of saline ice. The upper boundary limit in each case represents 1- to 2-ppt salinity ice for temperature range -4C to -27C, while the lower boundary represents 7- to 9-ppt salinity ice for the same temperature. The salinity, density, and petrographic structure of the 7- to 9-ppt natural seawater ice, which was grown in the laboratory, are closely identifiable with the characteristics of sea ice formed in a natural environment. This observation was based on comparison of the upper 44 cm of laboratory ice with a similar thickness of natural sea ice. The tensile strength was found to be a nonlinear function of temperature; there were strong implications, however, that a linear relationship with salinity may exist. The strength was found to be dependent on orientation of the stress field with both the grain (crystal) and subgrain (platelet) structure. Limited study indicates that the tensile strength of saline ice is appreciably reduced as stress rates increase above 25 psi/sec. (Author)