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Research Papers: Polar and Arctic Engineering

Probabilistic Analysis of Local Ice Loads on a Lifeboat Measured in Full-Scale Field Trials

[+] Author and Article Information
Md Samsur Rahman

Faculty of Engineering and Applied Science,
Memorial University of Newfoundland,
S. J. Carew Building,
Arctic Avenue,
St. John's, NL A1B 3X5, Canada
e-mail: msr303@mun.ca

Rocky S. Taylor

Centre for Arctic Resource Development, C-CORE,
Memorial University of Newfoundland,
Bartlett Building,
Morrissey Road,
St. John's, NL A1B 3X5, Canada
e-mail: rocky.taylor@card-arctic.ca

Allison Kennedy

National Research Council of Canada,
1 Arctic Avenue,
P.O. Box 12093,
St. John's, NL A1B 3T5, Canada
e-mail: Allison.Kennedy@nrc-cnrc.gc.ca

António Simões Ré

National Research Council of Canada,
1 Arctic Avenue,
P.O. Box 12093,
St. John's, NL A1B 3T5, Canada
e-mail: Antonio.SimoesRe@nrc-cnrc.gc.ca

Brian Veitch

Faculty of Engineering and Applied Science,
Memorial University of Newfoundland,
S. J. Carew Building,
Arctic Avenue,
St. John's, NL A1B 3X5, Canada

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 November 26, 2014; final manuscript received March 13, 2015; published online May 20, 2015. Assoc. Editor: Søren Ehlers.

J. Offshore Mech. Arct. Eng 137(4), 041501 (Aug 01, 2015) (14 pages) Paper No: OMAE-14-1146; doi: 10.1115/1.4030184 History: Received November 26, 2014; Revised March 13, 2015; Online May 20, 2015

This paper presents an analysis of local ice loads measured during full-scale field trials conducted in 2014 with a totally enclosed motor propelled survival craft (TEMPSC) in controlled pack ice conditions. These data were collected as part of an ongoing research program that aims to identify the limitations of conventional TEMPSC operating in sea ice environments and to provide insight as to how these limitations might be extended. During the 2014 trials, local ice loads were measured at two locations on the TEMPSC's bow area. These loads were the most severe measured to date and corresponded to an average ice floe mass that was approximately 1.25 times the mass of the fully loaded TEMPSC. The event-maximum method of local ice pressure analysis was used to analyze these field data to improve understanding of the nature of ice loads for such interactions and to evaluate the suitability of this approach for design load estimation for TEMPSCs (i.e., lifeboats) in ice. The event-maximum method was adapted for the present application, so as to link exceedance probabilities with design load levels for a given scenario. Comparison of the 2014 results with a previous analysis of 2013 field trials data supports earlier conclusions that these interactions are highly influenced by kinetic energy, since more massive ice floes are observed to impart significantly higher loads on the lifeboats. Illustrative examples examining the influence of ice concentration and sail-away distance have also been provided. The work establishes links between extreme loads and the exposure of the lifeboat to ice for different operating conditions. Based on this work it is concluded that the event-maximum method provides a promising approach for establishing risk-based design criteria for lifeboats if field data are available which adequately represent ice conditions encountered during the design life of the lifeboat.

Copyright © 2015 by ASME
Topics: Stress , Ice
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References

Kennedy, A., Simões Ré, A., and Veitch, B., 2010, “Operational Limitations of Conventional Lifeboats Operating in Sea Ice,” Proceedings of ICETECH, Anchorage, AK, Paper No. ICETECH10-103-RF.
Bercha, F., 2008, “State of Art of Arctic EER,” Proceedings of the 8th International Conference and Exhibition on Performance of Ships and Structures in Ice (ICETECH 2008), Banff, AB, Canada, Paper No. 121-RF.
International Organization for Standardization (ISO 19906,), 2010, Petroleum and Natural Gas Industries—Arctic Offshore Structures.
Jordaan, I. J., Maes, M. A., Browne, P. W., and Hermans, I. P., 1993, “Probabilistic Analysis of Local Ice Pressures,” ASME J. Offshore Mech. Arct. Eng., 115(1), pp. 83–89. [CrossRef]
Taylor, R. S., Jordaan, I. J., Li, C., and Sudom, D., 2010, “Local Design Pressures for Structures in Ice: Analysis of Full-Scale Data,” ASME J. Offshore Mech. Arct. Eng., 132(3), p. 031502. [CrossRef]
Kennedy, A., 2010, “Limitations of Lifeboats Operating in Ice Environments,” Master of Engineering thesis, Memorial University of Newfoundland, Faculty of Engineering and Applied Science, St. John's, NL, Canada.
Simões Ré, A., Veitch, B., Kuczora, A., Barker, A., Sudom, D., and Gifford, P., 2011, “Field Trials of a Lifeboat in Ice and Open Water Conditions,” Proceedings of the Port and Ocean Engineering Under Arctic Conditions, Montréal, QC, Canada.
Simões Ré, A., Veitch, B., Gifford, P., Kennedy, E., Kirby, C., Kuczora, A., and Sudom, D., 2012, “Performance and Survivability of Totally Enclosed Motor Propelled Survival Craft (TEMPSC) in Ice and Open Water Conditions,” Ocean, Coastal and River Engineering Portfolio, Paper No. OCRE-TR-2012-07.
Kennedy, A., Simões Ré, A., and Veitch, B., 2014, “Peak Ice Loads on a Lifeboat in Pack Ice Conditions,” Proceedings of the Arctic Technology Conference, Houston, TX.
Billard, R., Rahman, M. S., Kennedy, A., Simões Ré, A., and Veitch, B., 2014, “Operability of Lifeboats in Pack Ice: Coxswains' Skill and Design Factors,” Proceedings of Arctic Technology Conference, Houston, TX, Paper No. OTC 24610.
Rahman, M. S., Taylor, R. S., Simões Ré, A., Kennedy, A., Wang, J., and Veitch, B., 2014, “Probabilistic Analysis of Local Ice Loads on a Lifeboat,” Banff, AB, Canada.

Figures

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Fig. 1

DGPS plot of a single test

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Fig. 2

Impact loads and speed of the same test

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Fig. 3

Expanded load–time traces (section marked as A in Fig. 4)

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Fig. 4

Histogram of stem loads for all 2013 tests

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Fig. 5

Histogram of stem loads of 2013 tests at high ice concentration

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Fig. 6

Histogram of stem loads of 2013 tests at medium ice concentration

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Fig. 7

Histogram of stem loads of 2013 tests at low ice concentration

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Fig. 8

Histogram of bow shoulder loads for all 2013 tests

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Fig. 9

Histogram of bow shoulder loads of 2013 tests at high ice concentration

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Fig. 10

Histogram of bow shoulder loads of 2013 tests at medium ice concentration

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Fig. 11

Histogram of bow shoulder loads of 2013 tests at low ice concentration

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Fig. 12

Histogram of stem loads for all 2014 tests

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Fig. 13

Histogram of stem loads of 2014 tests at high ice concentration

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Fig. 14

Histogram of stem loads of 2014 tests at medium ice concentration

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Fig. 15

Histogram of stem loads of 2014 tests at low ice concentration

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Fig. 16

Histogram of bow shoulder loads for all 2014 tests

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Fig. 17

Histogram of bow shoulder loads of 2014 tests at high ice concentration

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Fig. 18

Histogram of bow shoulder loads of 2014 tests at medium ice concentration

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Fig. 19

Histogram of bow shoulder loads of 2014 tests at low ice concentration

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Fig. 20

Individual ice piece impacts stem loads

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Fig. 21

Local pressure curve for impact events on the stem (2014)

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Fig. 22

Comparison of local pressure for impact events on the stem measured in 2013 and 2014 field tests

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Fig. 23

Local pressure curve for impact events on the bow shoulder

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Fig. 24

Comparison of local pressure for impact events on the bow shoulder measured in 2013 and 2014 field tests

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Fig. 25

Comparison of expected number of ice impacts per kilometer sail-away distance at stem area in two different ice thicknesses

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Fig. 26

Idealizations of different ice floe configurations of five-tenth ice concentration

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Fig. 27

Effect of number of impacts and sail-away distance on exposure (a) constant exposure (constant number of impacts and different sail-away distance) and (b) different exposures (constant sail-away distance and different number of impacts)

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Fig. 28

Threshold effect on the number of impacts in 2013 and 2014 test at five-tenth ice concentration

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Fig. 29

Comparison of estimated design pressure at stem for two different ice thicknesses

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Fig. 30

Impact load profile and deflection of compliant and stiff structure

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