Third Canadian Geotechnical Colloquium: Ice forces on wide structures

1980 ◽  
Vol 17 (1) ◽  
pp. 97-113 ◽  
Author(s):  
P. R. Kry
Keyword(s):  
Failure Modes ◽  
Ice Sheet ◽  
Movement Rates ◽  
Statistical Variations ◽  
Exploration Drilling ◽  
Structure Geometry ◽  
Relative Inability ◽  
Ice Failure ◽  
Ice Forces ◽  
Structure Width

Successful use of artificial islands as exploration drilling platforms in the southern Beaufort Sea requires an understanding of the interactions of ice sheets with wide structures. Ice forces exerted on wide structures arise from the mechanical processes inherent in particular ice failure modes as environmental stresses move an ice sheet past a structure. Four primary ice failure modes occur against wide structures: flexure, rubble formation, buckling, and crushing. The horizontal forces associated with these modes differ by more than two orders of magnitude depending on structure geometry, ice sheet properties, and ice movement rates. Structure width influences the occurrence of ice failure modes, the ice failure stresses, and the total forces that can be exerted on a structure by an ice sheet. The relative inability to clear failed ice around wide structures (compared with narrow structures) leads to rubble formation when ice movement is continuous. After consolidation, the resulting rubble field can amplify forces exerted on the structure. Increased structure width generally results in decreased expected forces per unit width of structure. For crushing, the most serious ice failure mode for island design, increased structure width generates the possibility of nonsimultaneous failure. The resulting averaging of statistical variations across the width leads to reduced expected stresses for wide compared to narrow structures.

scholarly journals In-Plane and Out-of Plane Failure of an Ice Sheet using Peridynamics

2020 ◽  
Vol 36 (2) ◽  
pp. 265-271 ◽  
Author(s):  
Bozo Vazic ◽  
Erkan Oterkus ◽  
Selda Oterkus
Keyword(s):  
Failure Modes ◽  
Ice Sheet ◽  
Offshore Structures ◽  
Mindlin Plate ◽  
Plane Case ◽  
Plane Failure ◽  
Structure Interaction ◽  
Winkler Elastic Foundation ◽  
Peridynamic Model ◽  
Out Of Plane

ABSTRACTWhen dealing with ice structure interaction modeling, such as designs for offshore structures/icebreakers or predicting ice cover’s bearing capacity for transportation, it is essential to determine the most important failure modes of ice. Structural properties, ice material properties, ice-structure interaction processes, and ice sheet geometries have significant effect on failure modes. In this paper two most frequently observed failure modes are studied; splitting failure mode for in-plane failure of finite ice sheet and out-of-plane failure of semi-infinite ice sheet. Peridynamic theory was used to determine the load necessary for inplane failure of a finite ice sheet. Moreover, the relationship between radial crack initiation load and measured out-of-plane failure load for a semi-infinite ice sheet is established. To achieve this, two peridynamic models are developed. First model is a 2 dimensional bond based peridynamic model of a plate with initial crack used for the in-plane case. Second model is based on a Mindlin plate resting on a Winkler elastic foundation formulation for out-of-plane case. Numerical results obtained using peridynamics are compared against experimental results and a good agreement between the two approaches is obtained confirming capability of peridynamics for predicting in-plane and out-of-plane failure of ice sheets.

Advances in Sea Ice Mechanics in the USA

1987 ◽  
Vol 40 (9) ◽  
pp. 1232-1242 ◽  
Author(s):  
Devinder S. Sodhi ◽  
Gordon F. N. Cox
Keyword(s):  
Sea Ice ◽  
Thickness Distribution ◽  
Failure Process ◽  
Field Measurements ◽  
Small Scale ◽  
Ice Thickness ◽  
Ice Drift ◽  
Sea Ice Drift ◽  
Ice Failure ◽  
Ice Forces

A brief review of significant advances in the field of sea ice mechanics in the United States is presented in this paper. Emphasis is on ice forces on structures, as the subject relates to development of oil and gas resources in the southern Beaufort Sea. The main topics discussed here are mechanical properties, ice–structure interaction, modeling of sea ice drift, and oil industry research activities. Significant advances in the determination of ice properties are the development of testing procedures to obtain consistent results. Using stiff testing machines, researchers have been able to identify the dependence of tensile and compressive strengths on different parameters, eg, strain rate, temperature, grain size, c-axis orientation, porosity, and state of stress (uniaxial or multiaxial). Now reliable data exist on the tensile and compressive strengths of first-year and multi-year sea ice. Compressive strengths obtained from field testing of large specimens (6 × 3 × 2 m thick) were found to be within 30% of the strengths obtained from small samples tested in laboratory at the same temperature and strain rate as found in the field. Recent advances in the development of constitutive relations and yield criteria have incorporated the concept of damage mechanics to include the effect of microfracturing during the ice failure process. Ice forces generated during an ice–structure interaction are related to ice thickness and properties by conducting analytical or small-scale experimental studies, or both. Field measurements of ice forces have been made to assess the validity of theoretical and small-scale experimental results. There is good agreement between theoretical and small-scale experimental results for ice forces on conical structures. Theoretical elastic buckling loads also agree with the results of small-scale experiments. Though considerable insight has been achieved for ice crushing failure, estimation of ice forces for this mode is based on empirical relations developed from small-scale experiments. A good understanding of the ice failure process has been achieved when ice fails in a single failure mode, but our understanding of multi-modal ice failure still remains poor. Field measurements of effective pressure indicate that it decreases with increasing contact area. Research in fracture mechanics and nonsimultaneous failure is underway to explain this observed trend. Ice ridge formation and pile-up have been modeled, and the forces associated with these processes are estimated to be low. The modeling of sea ice drift has progressed to a point where it is able to determine the extent, thickness distribution, and drift velocity field of sea ice over the entire arctic basin. Components of this model relate to momentum balance, thermodynamic processes, ice thickness distribution, ice strength, and ice rheology.

AN ASSESSMENT OF STIFFENED COMPOSITE FUSELAGE PANELS BASED ON THE ROBUSTNESS PARAMETER

2010 ◽  
Vol 10 (04) ◽  
pp. 717-736
Author(s):  
MERRILL C. W. LEE ◽  
ZOLTAN MIKULIK ◽  
DONALD W. KELLY ◽  
RODNEY S. THOMSON
Keyword(s):  
Composite Structures ◽  
Failure Modes ◽  
Design Guidelines ◽  
Stochastic Algorithms ◽  
Buckling Modes ◽  
Statistical Variations ◽  
Stiffened Composite Panels ◽  
Final Design ◽  
Input Variables ◽  
The Impact

The European Commission 6th Framework Project COCOMAT was a four-and-a-half-year project (2004 to mid-2008) aimed at exploiting the large reserve of strength in composite structures through more accurate prediction of collapse. In the experimental work packages, significant statistical variations in buckling behaviour and ultimate loading were encountered. During the experiments for the COCOMAT project, it was recognised that there was a gap in knowledge about the effect of initial defects and variations in the input variables of both the experimental and simulated panels. The effect of the defects and variations in the experimental panel resulted in some failure modes that were not predicted with the finite element modelling. This led to the development of stochastic algorithms to relate variations in boundary conditions, material properties and geometries to the variation in buckling modes and compression loads up to the first failure. This paper shows the development of a stochastic methodology to identify the impact of variation in input parameters on the response of stiffened composite panels and the development of a robust index to support the evaluation of panel designs. The stochastic analysis included the generation of metamodels that allow quantification of the impact that the inputs have on the response using two first order variables, influence and sensitivity. These variables were then used to derive the robust indices to quantify the response of two COCOMAT panels that were experimentally tested, including the response of the panels to simulated damage. The robust indices that are shown in this paper are functions of the robustness parameter which has been recommended in the final Design Guidelines for the COCOMAT project to measure the effects of scatter found in postbuckling loads.

Dynamic Ice Force Analysis on a Conical Structure Based on Direct Observation and Measurement

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Ning Xu ◽  
Qianjin Yue
Keyword(s):  
Video Camera ◽  
Temporal Variations ◽  
Qualitative Description ◽  
Basic Model ◽  
Broken Ice ◽  
Conical Structure ◽  
Ice Failure ◽  
Ice Force ◽  
Bending Failure ◽  
Ice Forces

In order to study dynamic ice force induced by ice-structure interaction, we adopted the most reliable method to directly measure ice force on full-scale structure. This paper mainly demonstrates the qualitative description on the basic model for dynamic ice forces based on direct measurement on the jackets with ice-breaking cone in the Bohai Sea. Temporal variations of ice force are recorded by the ice load panels, and corresponding ice failure processes on conical structures are recorded by video camera. It is found that, when an ice sheet acts on the upward narrow cone, bending failure occurs and broken ice pieces are completely cleared up by the side of the cone. The basic form of dynamic ice force in time domain is a series of impulse signals with minimum load of zero.

scholarly journals Semi-brittle rheology and ice dynamics in DynEarthSol3D

2016 ◽  
Author(s):  
Liz C. Logan ◽  
Luc L. Lavier ◽  
Eunseo Choi ◽  
Eh Tan ◽  
Ginny A. Catania
Keyword(s):  
Ice Sheet ◽  
Initial Boundary ◽  
Constitutive Law ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Material Condition ◽  
Dynamic Regions ◽  
Material Conditions ◽  
Ice Failure ◽  
Sheet Deformation

Abstract. We present a semi-brittle rheology and explore its potential for simulating glacier and ice sheet deformation using a numerical model DynEarthSol3D (DES). DES is a finite element solver for the dynamic and quasi-static simulation of continuous media. The experiments within demonstrate that DES can simulate ice failure and deformation in dynamic regions of glaciers, especially at quickly changing boundaries such as where glaciers meet the ocean. We explore the effect that different initial, boundary, and material conditions have on ice flow and failure. We find that the use of a semi-brittle constitutive law is a necessary material condition to form the characteristic pattern of basal crevasse-aided pinch-and-swell geometry, which is observed globally in floating portions of ice and can often aid in eroding the ice sheet margins in direct contact with oceans.

scholarly journals A Numerical Ice Load Prediction Model Based on Ice-Hull Collision Mechanism

2020 ◽  
Vol 10 (2) ◽  
pp. 692
Author(s):  
Meng Zhang ◽  
Karl Garme ◽  
Magnus Burman ◽  
Li Zhou
Keyword(s):  
Failure Modes ◽  
Impact Load ◽  
Infinite Plate ◽  
Design Parameters ◽  
Load Prediction ◽  
Impact Location ◽  
Crushing Force ◽  
Broken Ice ◽  
Level Ice ◽  
Ice Failure

A simplified numerical model is introduced to predict ice impact force acting on the ship hull in level ice condition. The model is based on ice-hull collision mechanisms and the essential ice breaking characteristics. The two critical ice failure modes, localized crushing and bending breaking, are addressed. An energy method is used to estimate the crushing force and the indentation displacement for different geometry schemes of ice-ship interaction. Ice bending breaking scenario is taken as a semi-infinite plate under a distributed load resting on an elastic foundation. An integrated complete ice-hull impact event is introduced with ice failure modes and breaking patterns. Impact location randomness and number of broken ice wedges are considered in order to establish a stochastic model. The analysis is validated by comparison with the model ice test of a shuttle passenger ferry performed in May 2017 for SSPA Sweden AB at Aker Arctic Technology Inc. Good agreement is achieved with appropriate parameter selection assumed from the model test and when ice bending failure is dominant. This model can be used to predict the ice impact load and creates a bridge between design parameters (ice properties and ship geometry) and structure loads.

Ice Sheet Indentation Resistance in the Creep Domain

1986 ◽  
Vol 108 (1) ◽  
pp. 25-28
Author(s):  
B. Ladanyi
Keyword(s):  
Failure Modes ◽  
Wide Spectrum ◽  
Ice Sheet ◽  
Offshore Structure ◽  
Plastic Type ◽  
Out Of Plane ◽  
Creep Deformations ◽  
Limiting Case

The force exerted by a moving ice sheet on an offshore structure is known to vary strongly with the geometrical conditions at the contact with the structure and with the rate of ice movement, resulting in a wide spectrum of failure modes including both in-plane and out-of-plane failures of either brittle or plastic type. In this paper attention is concentrated to only one limiting case, in which the ice sheet moves so slowly that no fracture occurs at the contact with the structure, but the ice undergoes only in-plane creep deformations.

scholarly journals A simple stress-based cliff-calving law

2018 ◽  
Author(s):  
Tanja Schlemm ◽  
Anders Levermann
Keyword(s):  
Stress Field ◽  
Yield Stress ◽  
Sea Level ◽  
Water Depth ◽  
Ice Sheet ◽  
Two Dimensional ◽  
Loss Mechanism ◽  
Relative Water ◽  
Calving Rate ◽  
Ice Failure

Abstract. Over large coastal regions in Greenland and Antarctica the ice sheet calves directly into the ocean. In contrast to ice-shelf calving, an increase in cliff calving directly contributes to sea-level rise and a monotonously increasing calving rate with ice thickeness can constitute a self-amplifying ice loss mechanism that may significantly alter sea-level projections both of Greenland and Antarctica. Here we seek to derive a minimalistic stress-based parameterization for cliff calving. To this end we compute the stress field for a glacier with a simplified two-dimensional geometry from the two-dimensional Stokes equation. First we assume a constant yield stress to derive the failure region at the glacier front from the stress field within the ice sheet. Secondly, we assume a constant response time of ice failure due to exceedance of the yield stress. With this strongly constraining but very simple set of assumption we propose a cliff-calving law where the calving rate follows a power-law dependence on the freeboard of the ice with exponents between 2 and 3 depending on the relative water depth at the calving front. The critical freeboard below which the ice front is stable decreases with increasing relative water depth of the calving front. For a dry water front it is, for example, 75m. The purpose of this study is not to provide a comprehensive calving law, but to derive a particularly simple equation with a transparent and minimalistic set of assumptions.

Main Factors of Ice Sheet-Conical Structure Interaction Process Based on Field Monitoring

2009 ◽  
Author(s):  
Ning Xu ◽  
Yan Qu ◽  
Qianjin Yue ◽  
Xiangjun Bi ◽  
Andrew Clennel Palmer
Keyword(s):  
Ice Sheet ◽  
Field Work ◽  
Interaction Process ◽  
Structure Interaction ◽  
Interaction Processes ◽  
Ice Conditions ◽  
Conical Structure ◽  
Ice Loads ◽  
Ice Forces ◽  
Conical Structures

Ice-structure interaction plays a central part in determining ice loads and ice-induced vibrations. This is a controversial research issue, and many factors make the problem more complicated. The authors have been monitoring several ice resistant structures in the Bohai Sea for twenty years, and have measured ice forces and simultaneously observed ice-structure interaction processes. This paper describes typical physical ice sheet-conical structure interaction processes, field data and theoretical explanations, for different ice conditions and structure dimensions. The conclusions are more widely applicable, and we relate them to field work on ice-resistant conical structures in other ice-covered regions. Further work will quantify ice loads on conical structures once the interaction process is understood.

Ice Action on Two Cylindrical Structures

1984 ◽  
Vol 106 (1) ◽  
pp. 107-112 ◽  
Author(s):  
K. Kato ◽  
D. S. Sodhi
Keyword(s):  
Dominant Frequency ◽  
Small Scale ◽  
Interference Effects ◽  
Cylindrical Structures ◽  
Structure Interaction ◽  
Individual Structure ◽  
The Individual ◽  
Ice Failure ◽  
Ice Force ◽  
Ice Forces

Ice action on two cylindrical structures, located side by side, has been investigated in a small-scale experimental study to determine the interference effects on the ice forces generated during ice structure interaction. The proximity of the two structures changes the mode of ice failure, the magnitude and direction of ice forces on the individual structure, and the dominant frequency of ice force variations. Interference effects were determined by comparing the experimental results of tests at different structure spacings.

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