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Research Papers: Polar and Arctic Engineering

Model Tests With a Compliant Cylindrical Structure to Investigate Ice-Induced Vibrations

[+] Author and Article Information
Gesa Ziemer

HSVA Hamburgische
Schiffbau-Versuchsanstalt GmbH,
Bramfelder Straße 164,
Hamburg 22305, Germany
e-mail: ziemer@hsva.de

Karl-Ulrich Evers

HSVA Hamburgische
Schiffbau-Versuchsanstalt GmbH,
Bramfelder Straße 164,
Hamburg 22305, Germany
e-mail: evers@hsva.de

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 December 1, 2015; final manuscript received May 15, 2016; published online June 17, 2016. Assoc. Editor: Søren Ehlers.

J. Offshore Mech. Arct. Eng 138(4), 041501 (Jun 17, 2016) (8 pages) Paper No: OMAE-15-1124; doi: 10.1115/1.4033712 History: Received December 01, 2015; Revised May 15, 2016

A compliant cylindrical structure has been built and tested in a series of model tests in ice in the Large Ice Model Basin at HSVA. The structure's stiffness in ice plane is higher in ice drift direction than crosswise, enabling the model to vibrate in different geometrical oscillation patterns. In total, four ice sheets have been used to perform tests in different ice thickness, covering a wide range of ice drift velocities between 0.005 and 0.15 m/s in model scale. Several events of ice-induced vibrations were observed throughout the test campaign. Oscillations are found to reach different types of beginning steady states, depending on ice drift velocity and ice thickness. Dynamic amplification of structural response in ice plane as well as ratio of static and dynamic forces is highly dependent on the type of vibration. While the dynamic amplification is highest when the ice load's frequency equals the first natural frequency of the structure, the highest dynamic forces occur when the crushing frequency is an integer fraction of the natural frequency. The paper describes the design of the test setup, instrumentation and calibration, performance and analysis of conducted tests, and general findings.

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Copyright © 2016 by ASME
Topics: Ice , Vibration , Stress
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References

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Figures

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Fig. 1

Drawing of the SDOF model

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Fig. 2

Response spectra of plucking test in x-direction, performed in the ice-free basin (top) and in y-direction, performed in dry condition (bottom)

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Fig. 3

Bending at 0.05 m/s (left), buckling at 0.05 m/s (middle), and crushing at 0.15 m/s (right). Cross sections of the approaching ice sheet and location of failure are indicated to illustrate their shape and location.

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Fig. 4

Acceleration in y-direction plotted against acceleration in x-direction (random vibration event)

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Fig. 5

Response during straight vibration event

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Fig. 6

Spectra of response (left) and ice load (right) during straight vibration event

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Fig. 7

Acceleration in y-direction plotted against acceleration in x-direction (circular vibration event)

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Fig. 8

Acceleration in y-direction plotted against acceleration in x-direction (periodic vibration event)

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Fig. 9

Time histories and spectra of load and response during periodic vibration event

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Fig. 10

Variation of contact during periodic vibration event

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Fig. 11

Ice drift velocity and ice thickness facilitating ice-induced vibrations with beginning steady-state. Shaded areas represent tested conditions.

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Fig. 12

Dynamic amplification of response versus dominant response frequency. Dashed lines mark interval where lock-in is expected according to Kärnä [20].

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Fig. 13

Dynamic load versus mean load. Straight lines limit area of expected forces based on ISO 19906 [14].

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Fig. 14

Load and displacement during straight vibration event (top) and periodic vibration event (bottom)

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