Scale Effect in Ice Flexural Strength

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Mohamed Aly ◽  
Rocky Taylor ◽  
Eleanor Bailey Dudley ◽  
Ian Turnbull
Keyword(s):  
Flexural Strength ◽  
Sea Ice ◽  
Probabilistic Models ◽  
Scale Effects ◽  
Offshore Structures ◽  
Bridge Piers ◽  
Freshwater Ice ◽  
Flexural Failure ◽  
Ice Loads ◽  
Ice Strength

Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ice-class ships, sloped offshore structures, and sloped bridge piers. While scale effects in compressive ice strength are well known, there has been debate as to the extent of scale effects in ice flexural strength. To investigate scale effects during flexural failure of both freshwater and saline ice, a comprehensive up-to-date database of beam flexural strength measurements has been compiled. The database includes 2073 freshwater ice beam tests with beam volumes between 0.00016 and 2.197 m3, and 2843 sea ice beam tests with volumes between 0.00048 and 59.87 m3. The data show a considerable decrease in flexural strength as the specimen size increases, when examined over a large range of scales. Empirical models of freshwater ice flexural strength as a function of beam volume, and of saline ice as function of beam and brine volumes have been developed using regression analysis. For freshwater ice, the scale-dependent flexural strength is given as: σf=839(V/V1)−0.13 For sea ice, the dependence of flexural strength has been modeled as: σ=1324(V/V1)−0.054e−4.969vb. Probabilistic models based on the empirical data were developed based on an analysis of the residuals, and can be used to enhance probabilistic analysis of ice loads where ice flexural strength is an input.

Scale Effect in Freshwater Ice Flexural Strength

2018 ◽  
Author(s):  
Mohamed Aly ◽  
Rocky Taylor ◽  
Eleanor Bailey Dudley ◽  
Ian Turnbull
Keyword(s):  
Flexural Strength ◽  
Large Range ◽  
Scale Effects ◽  
Offshore Structures ◽  
Bridge Piers ◽  
Considerable Decrease ◽  
Freshwater Ice ◽  
Flexural Failure ◽  
Ice Loads ◽  
Ice Strength

Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ice-class ships, sloped offshore structures or sloped bridge piers. While scale effects are well known for compressive ice strength, there has been debate as to whether or not scale effects in ice flexural strength exist. To investigate scale effects during flexural failure of freshwater ice, a comprehensive up-to-date database of beam flexural strength measurements has been compiled. The data show a considerable decrease in flexural strength as the specimen size increases, when examined over a large range of scales. An empirical model of freshwater ice flexural strength as a function of beam volume has been developed using regression analysis.

Methodology to Evaluate Sea Ice Loads for Seasonal Operations

2015 ◽  
Author(s):  
Jan Thijssen ◽  
Mark Fuglem
Keyword(s):  
Sea Ice ◽  
Offshore Structures ◽  
Ice Thickness ◽  
Safety Level ◽  
Site Specific ◽  
Design Load ◽  
Ice Load ◽  
Ice Conditions ◽  
Design Loads ◽  
Ice Loads

Offshore structures designed for operation in regions where sea ice is present will include a sea ice load component in their environmental loading assessment. Typically ice loads of interest are for 10−2, 10−3 or 10−4 annual probability of exceedance (APE) levels, with appropriate factoring to the required safety level. The ISO 19906 standard recommends methods to determine global sea ice loads on vertical structures, where crushing is the predominant failure mode. Fitted coefficients are proposed for both Arctic and Sub-Arctic (e.g. Baltic) conditions. With the extreme ice thickness expected at the site of interest, an annual global sea ice load can be derived deterministically. Although the simplicity of the proposed relation provides quick design load estimates, it lacks accuracy because the only dependencies are structure width, ice thickness and provided coefficients; no consideration is given to site-specific sea ice conditions and the corresponding exposure. Additionally, no term is provided for including ice management in the design load basis. This paper presents a probabilistic methodology to modify the deterministic ISO 19906 relations for determining global and local first-year sea ice loads on vertical structures. The presented methodology is based on the same ice pressure data as presented in ISO 19906, but accounts better for the influence of ice exposure, ice management and site-specific sea ice data. This is especially beneficial for ice load analyses of seasonal operations where exposure to sea ice is limited, and only thinner ice is encountered. Sea ice chart data can provide site-specific model inputs such as ice thickness estimates and partial concentrations, from which corresponding global load exceedance curves are generated. Example scenarios show dependencies of design loads on season length, structural geometry and sea ice conditions. Example results are also provided, showing dependency of design loads on the number of operation days after freeze-up, providing useful information for extending the drilling season of MODUs after freeze-up occurs.

Experimental Study of Sea Ice Forces on a Structure and its Stability

2011 ◽  
Vol 243-249 ◽  
pp. 4750-4753 ◽  
Author(s):  
Ji Wu Dong ◽  
Zhi Jun Li ◽  
Li Min Zhang ◽  
Guang Wei Li ◽  
Hong Wei Han
Keyword(s):  
Experimental Study ◽  
Sea Ice ◽  
Offshore Structures ◽  
Sea Bed ◽  
Ice Loads ◽  
Level Ice ◽  
Ice Floes ◽  
The Stability ◽  
Ice Forces ◽  
Concrete Model

A structure was designed to reduce the large forces exerted by level ice on offshore structures in shallow icy waters, by breaking the large ice floes into small pieces from flexing-induced failure. A series of model tests was conducted to simulate ice loads on the structure. A concrete model of it was adopted to verify the stability of the structure under the action of ice floes, which had five different thicknesses. The results show that ice forces on the structure are low and that the stability of the structure under different sea bed is good.

Engineering Properties of Sea Ice Ridges in the Barents Sea in 2012-2014 Years for Evaluation of Ice Loads on Offshore Structures

2015 ◽  
Vol 725-726 ◽  
pp. 263-269
Author(s):  
Kseniia Gorbunova ◽  
Karl Shkhinek
Keyword(s):  
Sea Ice ◽  
Barents Sea ◽  
Offshore Structures ◽  
Field Conditions ◽  
Engineering Properties ◽  
The South ◽  
Svalbard Archipelago ◽  
Layer Height ◽  
The Barents Sea ◽  
Ice Loads

Results of studies of ice ridges in field conditions are presented. Ice ridges investigated in the Barents Sea the proximity of the South-East of Svalbard archipelago. Five ice ridges are surveyed during research cruises in 2012-2014 years. Main engineering properties ice ridges as thickness of consolidated layer, height of sail and depth of keel were obtained. Results of research are of primary importance for evaluation of ice loads in studied area in Barents Sea.

The influence of beam size on the flexural strength of sea ice, freshwater ice and iceberg ice

1992 ◽  
Vol 66 (6) ◽  
pp. 1017-1036 ◽  
Author(s):  
B. L. Parsons ◽  
M. Lal ◽  
F. M. Williams ◽  
J. P. Dempsey ◽  
J. B. Snellen ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Sea Ice ◽  
Beam Size ◽  
Freshwater Ice

Review of Ice Load Standards and Comparison With Measurements

2017 ◽  
Author(s):  
Leon Kellner ◽  
Hauke Herrnring ◽  
Michael Ring
Keyword(s):  
Sea Ice ◽  
Offshore Structures ◽  
Classification Rules ◽  
Empirical Formulas ◽  
Ice Load ◽  
Ice Coverage ◽  
Ice Loads ◽  
Full Scale Tests ◽  
The Given

Sea ice can interact with offshore structures in regions with at least seasonal ice coverage. Therefore the prediction of ice loads on offshore structures is required by many standards or classification rules and guidelines. In order to do this, empirical formulas are often prescribed. These are based on assumptions in combination with model or full scale tests. Yet there are very few publications where the results of the formulas are actually compared to measurements. A case study is made for ice loads on the Norströmsgrund lighthouse. First of all current empirical formulas given by standards bodies or classification societies are reviewed with focus on applicability. Secondly, the ice loads predicted by the empirical formulas are compared to measurements. It was found that for the given case most methods significantly overestimate the load. The applicability of some methods is disputable.

scholarly journals A review of discrete element simulation of ice–structure interaction

2018 ◽  
Vol 376 (2129) ◽  
pp. 20170335 ◽  
Author(s):  
Jukka Tuhkuri ◽  
Arttu Polojärvi
Keyword(s):  
Sea Ice ◽  
Failure Process ◽  
Discrete Element ◽  
Offshore Structures ◽  
Lessons Learned ◽  
Structure Interaction ◽  
Large Numbers ◽  
Ice Loads ◽  
Discontinuous Medium ◽  
Ice Failure

Sea ice loads on marine structures are caused by the failure process of ice against the structure. The failure process is affected by both the structure and the ice, thus is called ice–structure interaction. Many ice failure processes, including ice failure against inclined or vertical offshore structures, are composed of large numbers of discrete failure events which lead to the formation of piles of ice blocks. Such failure processes have been successfully studied by using the discrete element method (DEM). In addition, ice appears in nature often as discrete floes; either as single floes, ice floe fields or as parts of ridges. DEM has also been successfully applied to study the formation and deformation of these ice features, and the interactions of ships and structures with them. This paper gives a review of the use of DEM in studying ice–structure interaction, with emphasis on the lessons learned about the behaviour of sea ice as a discontinuous medium. This article is part of the theme issue ‘Modelling of sea-ice phenomena’.

Interaction of Ships and Ocean Structures With Ice Loads and Stochastic Ocean Waves

2007 ◽  
Vol 60 (5) ◽  
pp. 246-289 ◽  
Author(s):  
R. A. Ibrahim ◽  
N. G. Chalhoub ◽  
Jeffery Falzarano
Keyword(s):  
Probabilistic Models ◽  
Research Work ◽  
Ocean Waves ◽  
Offshore Structures ◽  
Review Article ◽  
Future Research ◽  
Impact Loads ◽  
Floating Structure ◽  
Research Activities ◽  
Ice Loads

The influence of floating ice on the dynamic behavior of ships and offshore structures depends on many factors such as ice thickness and its relative speed with respect to the floating structure. The ice resistance to ship motion forms an essential problem in ship design and navigation. Furthermore, local or global ice loads acting on ocean systems are random and nonsmooth when impact interaction takes place. Impact loads on the bow of a ship navigating in solid ice may be modeled by a Poisson law. The measured stress amplitudes on the ship frame at the bow follow an exponential distribution. The nonhomogeneity and difference in ice microstructure, as well as the influence of salt and temperature, result in a great uncertainty in the ice strength. Therefore, the current review article aims at assessing the ice related problems encountered by offshore structures as well as by ships during their navigation. It also discusses the impacts of local and global ice loads on floating structures and reviews their existing probabilistic models. Moreover, this article covers the dynamic interaction of ice with flexible and rigid structures, and ships. In view of ice loads on marine systems, new design regulations have been introduced by international organizations that are involved in the design and building of ships as well as offshore structures. The ship stochastic stability and the first-passage roll stabilization problem associated with random ocean waves will also be described in an attempt to stimulate future research work dealing with ice impact loads. Moreover, due to the lack of research activities addressing the control problem of ships operating in icy waters, the current article will briefly discuss passive and active control schemes developed for controlling the ship roll motion. There are 529 references cited in this review article.

Full-Scale In-Situ Four-Point Beam Bending Field Tests on Sea Ice

2021 ◽  
Author(s):  
Rocky Taylor ◽  
Ian Turnbull ◽  
Eleanor Bailey-Dudley ◽  
Rob Pritchett
Keyword(s):  
Flexural Strength ◽  
Sea Ice ◽  
Scale Effects ◽  
Field Tests ◽  
Basic Material ◽  
Measured Temperature ◽  
Full Thickness ◽  
Loading System ◽  
Beam Bending

Abstract The flexural strength of ice is not a basic material property, but rather is an estimate of the maximum stress in the outermost fiber of an ice specimen when it fails in bending. Such conditions correspond to a number of important engineering applications, such as interactions between ice and a sloping structure or between ice and ships. Ice flexural strength is therefore highly important for calculating ice pressures and forces of interest for engineering design. While there has been considerable discussion in the literature regarding scale effects related to ice crushing against a vertical structure, scale effects in relation to bending failure have received much less attention. To this end, more flexural strength data for large, full-thickness sea ice beams are needed. To address these data gaps, a field data collection program was carried out in Pistolet Bay, Newfoundland over two field seasons (2017–2018). During this program, large sea ice beams were tested in-situ using a custom four-point bending apparatus, which was comprised of several main subsystems (e.g., the ram loading system, the platen, the ubrackets, and the hydraulic system). The sea ice beams were completely cut free from the ice cover and loaded at four points, such that the center load is parallel, but opposed to, the loads at the ends of the beam. All tests were done in-situ so that no brine drainage took place and the temperature gradient remained consistent. Tests were carried out for several combinations of beam geometry, which were scaled relative to the ice thickness. In addition to flexural strength, during the Pistolet Bay field program, the physical properties of the ice were measured (temperature, salinity, density). In this paper, a description of the field apparatus, test program and results from the full-thickness in-situ four-point beam bending tests are presented, along with a discussion of practical implications and future work.

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