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Polar and Arctic Science and Technology

Modal Analysis of the Ice-Structure Interaction Problem

[+] Author and Article Information
Michael A. Venturella

 United States Coast Guard, 2100 Second Street, SW Washington, DC 20593

Mayuresh J. Patil, Leigh S. McCue

Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

J. Offshore Mech. Arct. Eng 133(4), 041501 (Apr 11, 2011) (18 pages) doi:10.1115/1.4003388 History: Received August 12, 2008; Revised October 21, 2010; Published April 11, 2011; Online April 11, 2011

In this paper the authors present a multimode ice-structure interaction model based on the single degree of freedom ice-structure interaction model initially proposed by Matlock (1969, “A Model for the Prediction of Ice-Structure Interaction,” Proceedings of the First Offshore Technology Conference, Houston, TX, Vol. 1, pp. 687–694, Paper No. OTC 1066; 1971, “Analytical Model for Ice Structure Interaction,” ASCE Journal of the Engineering Mechanics Division, EM4, pp. 1083–1092). The model created by Matlock assumed that the primary response of the structure would be in its fundamental mode of vibration. In order to glean a greater physical understanding of the ice-structure interaction phenomena, it was critical that this study set out to develop a multimode forced response for the pier when a moving ice floe makes contact at a specific vertical pier location. Modal analysis is used in this study, in which the response of each mode is superposed to find the complete modal response of the entire length of a pier subject to incremental ice loading. This incremental ice loading includes ice fracture points as well as loss of contact between ice and structure. In the work of Matlock , the physical system is a bottom supported pier modeled as a cantilever beam. Realistic conditions such as ice accumulation on the pier modeled as a point mass and uncertainties in the ice characteristics are introduced in order to provide a stochastic response. The impact of number of modes in modeling is studied as well as dynamics due to fluctuations of ice impact height as a result of typical tidal fluctuations. A Poincaré based analysis following on the research of Karr (1992, “Nonlinear Dynamic Response of a Simple Ice-Structure Interaction Model,” Proceedings of the 11th International Conference of Offshore Mechanics and Arctic Engineering, Vol. 4, pp. 231–237) is employed to identify any periodic behavior of the low and high velocity ice system responses. Recurrence plotting is also utilized to further define any existing structure of the ice-structure interaction time series for low and high speed ice floes. While the Matlock model on which this research is based is admittedly simplistic, the intention of this work is to provide a foundation for future work using time series analysis and modal analysis on more sophisticated models coupling multiple piers and connecting structure for a comprehensive ice-wind-structural dynamics model.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Dynamic ice-structure interaction model reproduced with permission (Matlock , 1969, 1971)

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Figure 2

Twenty mode multilocation simulation—low velocity ice impact at 192 in. (4.877 m)

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Figure 3

Poincaré map—low velocity ice at 192 in. (4.877 m) impact height

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Figure 4

Twenty mode multilocation simulation—high velocity ice impact at 192 in. (4.877 m)

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Figure 5

Poincaré map—high velocity ice impact at 192 in. (4.877 m)

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Figure 6

Ten mode multiple location—low velocity ice at 120 in. (3.048 m) impact height

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Figure 7

Poincaré map—low velocity ice at 120 in. (3.048 m) impact height

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Figure 8

Ten mode multiple location—high velocity ice at 120 in. (3.048 m) impact height

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Figure 9

Poincaré map–high velocity ice impact at 120 in. (3.048 m)

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Figure 10

Ten mode multiple location—low velocity ice at 160 in. (4.064 m) height

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Figure 11

Poincaré map—low velocity ice at 160 in. (4.064 m) impact height

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Figure 12

Ten mode multiple location—high velocity ice at 160 in. (4.064 m) height

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Figure 13

Poincaré map overlaid on phase plane—high velocity ice impact at 160 in. (4.064 m)

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Figure 14

Local recurrence plot (nondimensionalized)—low velocity ice impact at 192 in. (4.877 m)

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Figure 15

Local recurrence plot (nondimensionalized, reduced neighborhood size)—high velocity ice impact at 192 in. (4.877 m)

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Figure 16

Local recurrence plot (nondimensionalized, last 3 s)—low velocity ice impact at 120 in. (3.048 m)

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Figure 17

Local recurrence plot (nondimensionalized, reduced neighborhood size)—high velocity ice impact at 120 in. (3.048 m)

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Figure 18

Local recurrence plot (nondimensionalized, last 4 s)—low velocity ice impact at 160 in. (4.064 m)

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Figure 19

Local recurrence plot (nondimensionalized)—high velocity ice impact at 160 in. (4.064 m)

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Figure 20

Gaussian force/pitch—impact at 192 in. (4.877 m) height (with point mass)

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Figure 21

Gaussian force/pitch—impact at 192 in. (4.877 m) height (with point mass)

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Figure 22

Gaussian force/pitch—impact at 120 in. (3.048 m) height (with point mass)

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Figure 23

Gaussian force/pitch—impact at 120 in. (3.048 m) height (with point mass)

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Figure 24

Gaussian force/pitch—impact at 160 in. (4.064 m) height (with point mass)

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Figure 25

Gaussian force/pitch—impact at 160 in. (4.064 m) height (with point mass)

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