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Safer ships

Predicting the structural response of vessels and ice impacts

special feature: COASTS

Part of a special feature showcasing Memorial's leadership and expertise in cold ocean and Arctic science, technology and society (COASTS).

By Jackey Locke

As an island in the middle of the North Atlantic, Newfoundland and Labrador relies on ships to transport goods and people to and from mainland Canada, transport people within the province, for search and rescue, oil-spill response, sovereignty protection and other essential operations.

Often, these ships are low- or non-ice class vessels, which can pose significant problems given that the province is surrounded by ice-infested waters for more than six months of the year.

Vital links

This past April, two of Oceanex’s three cargo vessels servicing the island portion of the province, the Connaigra and the Sanderling, both impacted ice during regular operations.

Both required immediate repair, halting operations and narrowing a vital commercial link to the island. A few short months later, in June, the MV Veteran, which provides ferry services to Fogo and Change Islands on the Northeast Coast of the island, was damaged by ice and dry docked for repairs.

According to Dr. Bruce Quinton, a professor of ocean and naval architectural engineering in Memorial’s Faculty of Engineering and Applied Science, unexpected ice impacts have been prevalent in the province since the Arctic began experiencing record high temperatures.

Dr. Bruce Quinton
Dr. Bruce Quinton
Photo: Chris Hammond

This means a larger quantity of more dangerous, multi-year ice is free to move south offshore Newfoundland and Labrador’s waters, he says.

“Global warming means that ice will be a greater hazard than ever before. Multi-year ice, which is ice older than two years, normally trapped in the Arctic by more plentiful first-year ice, has greater geographic mobility due to the reduced extent of first-year ice,” Dr. Quinton said.

“Of additional concern is the response of low- and non-ice class vessels when they come in contact with undetected small pieces of glacial ice, commonly known as growlers, as this generally occurs at significant speed.”

New ice climate

Dr. Quinton’s research uses recent advances in engineering knowledge for predicting the hull structural response of vessels like the Connaigra, Sanderling and MV Veteran to ice impacts.

These new developments may be used by ship owners, operators, designers and policy-makers to mitigate the risks associated with operating in the new ice climate.

Dr. Quinton recently discovered that steel hulls respond very differently to moving, or sliding, hull loads than they do to stationary impacts, when the impact causes hull denting. He also discovered ship hulls are more likely to fracture under sliding ice loads.

Watch the short video below to watch part of Dr. Quinton’s ice load testing.

This is important because the sliding motion of hull loads is almost always ignored in calculations when considering the response of ships to accidental impact, which may lead to an overestimation of a vessel’s capabilities.

“Essentially, accidental moving, or sliding, hull loads incite a very different state of stress in the hull than loads of similar magnitude that do not slide,” said Dr. Quinton.

“The present state-of-the-art for design and analysis of ship hulls assumes that all impact loads are stationary, and do not slide on the hull. As we now know sliding loads cause varying states of stress, and that hull fracture varies with particular states of stress, not just an average measure of the stress magnitude, we are able to predict when moving, or sliding, loads will cause hull fracture. This would not be predicted correctly if the impact was analyzed as a stationary load.”

Dr. Quinton’s research has national and international reach since his findings apply to all ships operating in ice-infested waters. His research means a more accurate, overall prediction of the operational capabilities of existing low- and non-ice class ships and allows for the modification of new designs to minimize hull fracture in ice.

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