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The current offshore code, he notes, is based on the premise that pressures won’t increase in impacts above 100 mega Newtons. (For reference, the Hibernia platform offshore Newfoundland was de- signed for about 500 mega Newtons, and the highest controlled impact measured in a field program was about 17 mega Newtons.) “I believe that the whole event will scale up, and the total force will get larger, though I know there are differing views and healthy debate on the subject,” he says. Another view is that the size of the high-pressure zone is determined by the strength of the ice. “This is why we need to do research,” Dr. Daley adds. “This needs to be sorted out.” In the 1980’s, impacts were measured during major ice-loading events on plat- forms in the Beaufort Sea, but the high- pressure zones were not recorded due to the low spatial resolution technology that was available at the time. In STePS2, the ice-structure interactions will be meas- ured using an advanced technology im- pact module capable of withstanding the loads and capturing the pressure distribu- tions at high resolution. Developed by physicist Dr. Robert Gagnon at the National Research Coun- cil’s Institute for Ocean Technology (lo- cated next door to Memorial University’s Ocean and Naval Architectural Engineer- ing structures lab in St. John’s), the im- pact module consists of a high spatial res- olution array of pressure sensors covered by a thin metal sheet, against which the force is applied. These patented sensors rest on an 18- inch-thick block of clear acrylic that has a high-speed camera mounted behind it to capture the pressure information. Dr. Gagnon designed this unit following a field trial he and colleagues conducted offshore Newfoundland in 2001 that ac- quired data from 178 impacts on 18 ice masses ranging from 40-ton growlers (chunks of ice less than one meter above the surface) to a 22,000-ton iceberg at ship speeds up to 13 knots for the smaller masses. The impact module was developed in part to validate the design of a much larger impact panel intended to be mounted on the front of a vessel and rammed into icebergs during field trials. The impact module and preparations for the field study have cost about $1,000,000. If the rest of the required funding is secured, Dr. Gagnon plans to have the large impact panel mounted on the Canadian Coast Guard Services Terry Fox icebreaker for trials possibly in 2012, the centennial of the sinking of the Ti- tanic. Dr. Gagnon has for several years been developing technologies for meas- uring load and pressure, formulating new experimental techniques to study ice crushing behavior and developing nu- merical simulations of ice/ship collisions. Dr. Daley was able to capitalize on these strong and complementary backgrounds when drafting the proposal. In the experiments using the double- pendulum apparatus, the impact module will measure the impact force and pres- sure distribution when a five-ton steel pendulum collides with another equally massive one that has a 1-metre diameter ice sample attached to it, with forces up to 5 mega Newtons and at speeds up to 15 knots. The impact module will also record the stationary experiments, in which ice blocks will be crushed against a steel frame. In addition to the $1.2 million private- sector investment, STePS2 has also re- ceived $3 million through the Atlantic Canada Opportunities Agency’s Atlantic Innovation Fund. The Research and Development Cor- poration Newfoundland and Labrador is investing $800,000 through the Collabo- rative R&D Academic Program. Memo- rial University is contributing approximately $130,000 for student bur- saries through the School of Graduate Studies. Research funding agencies such as MITACS and NSERC are expected to provide approximately $500,000 through various programs that fund graduate stu- dent support. IOT-NRC is a research part- ner. In-kind partner contributions total $1.59 million. When the project concludes in 2015, the deliverable will be a design tool that enables Arctic ship and offshore structure designers, operators, and engineers to model a range of scenarios involving water, ice, and steel interactions, to spec- ify optimal design parameters. Reflecting on STePS2, Mr. Kendrick said, “I think St. John’s is a really excit- ing place for this type of work right now. Nobody that I know of is doing directly comparable things. Others are looking at aspects of the same problems in similar ways, but what Claude (Daley) is doing is, to my knowledge, unique.” 48 Maritime Reporter & Engineering News FEATURE OFFSHORE ANNUAL The small (3 feet tall) double-pendulum ice impact apparatus (photo: Peter Seifer t)
