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Research Papers: Polar and Arctic Engineering

On the Flexural Failure of Thick Ice Against Sloping Structures

[+] Author and Article Information
Fwu Chyi Teo

Department of Civil and Environmental
Engineering,
The National University of Singapore,
Block E1A, #07-03,
No.1 Engineering Drive 2
117576, Singapore
e-mail: a0074651@u.nus.edu

Leong Hien Poh

Department of Civil and Environmental
Engineering,
The National University of Singapore,
Block E1A, #07-03,
No.1 Engineering Drive 2
117576, Singapore
e-mail: leonghien@nus.edu.sg

Sze Dai Pang

Department of Civil and Environmental
Engineering,
The National University of Singapore,
Block E1A, #07-03,
No.1 Engineering Drive 2
117576, Singapore
e-mail: ceepsd@nus.edu.sg

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received July 9, 2016; final manuscript received January 4, 2017; published online May 5, 2017. Assoc. Editor: Søren Ehlers.

J. Offshore Mech. Arct. Eng 139(4), 041501 (May 05, 2017) (8 pages) Paper No: OMAE-16-1080; doi: 10.1115/1.4035771 History: Received July 09, 2016; Revised January 04, 2017

This paper investigates the breaking load of ice sheets up to 6 m thick, against a sloping structure. The reference model by Croasdale, which the design code is based on, neglects the edge moment arising from the loading eccentricity, as well as a second-order bending effect induced by the axial loading in its formulation. In this paper, the model is reformulated to incorporate these effects into the governing equation, as well as to account for the occurrence of local crushing at the point of contact between the ice sheet and sloping structure. For thin ice, predictions from the modified model resemble closely those by Croasdale's model. As the ice thickness increases, however, significant deviations from the reference model can be observed. For thick ice, the terms omitted for brevity in the reference model have a significant influence, without which the breaking load is under-estimated. It is furthermore demonstrated that against sloping structures, the dominant failure mode is that of flexural, except in very limiting cases where it switches to crushing.

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References

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Figures

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Fig. 1

Infinitesimal segment of elastic beam on elastic foundation. Parameter c denotes the spring constant of the elastic foundation, representing the buoyancy forces of sea water (c=ρwg).

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Fig. 2

Semi-infinite beam on elastic foundation subjected to loading from sloping structure. M0, V0, and H indicate the Neumann boundary conditions due to N and Ffr.

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Fig. 3

Local crushing at edge lowers the loading eccentricity, with D as the penetration depth, where he=(h/2)−(D tan θ/2) and the point of contact is at the midpoint of D  tan θ

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Fig. 4

Numerical framework to compute F0

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Fig. 5

Horizontal loads for slope of 60 deg. Material properties given in Sec. 3.1. The effect of axial term in Eq. (2) is indicated as (i), while that of local crushing is indicated as (ii).

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Fig. 6

Idealized crushing and shearing planes

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Fig. 7

Horizontal load versus thickness for “weak” ice and μ = 0.05 (combination 1). The vertical axis is in logarithmic scale.

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Fig. 8

Horizontal load versus thickness for “weak” ice and μ = 0.30 (combination 2). The triangle marks the point of transition from flexural failure to compressive failure. The vertical axis is in logarithmic scale.

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Fig. 9

Horizontal load versus thickness for “strong” ice and μ = 0.05 (combination 3). The vertical axis is in logarithmic scale.

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Fig. 10

Horizontal load versus thickness for “strong” ice and μ = 0.30 (combination 4). The vertical axis is in logarithmic scale.

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