Optimal design of bow plating for ships operating in ice

• Main Author: Brown, Peter Wilfred
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1993
• Subjects: Arctic
• Online Access: https://research.library.mun.ca/8020/; https://research.library.mun.ca/8020/1/Brown_PeterW.pdf; https://research.library.mun.ca/8020/3/Brown_PeterW.pdf

Extensive work has been carried out in recent years to ensure that ice-capable ships are both safe and economical. The present analysis provides a methodology which can be employed by the designer to calculate the optimum bow plating thickness for operation in ice. To this end, a local ice load model is re-evaluated using a probabilistic analysis of full scale data, probabilities of failure for plating are calculated and plate thickness is optimised. -- Full scale data for the MV Canmar Kigoriak and USCGC Polar Sea were ranked; curves were fitted through the tail of each data set; and Type-I extreme probability, distributions were derived for the three panel sizes. The Canmar Kigoriak data were then subdivided based on contact area and a simulation was performed to derive the load distributions on subregions of the instrumented panel. Finally, a local ice load model which accounts for annual number of impacts and exposure was confirmed. -- To evaluate the strength of bow plating, three limit states (three-hinge collapse, permanent set and membrane collapse) were selected. Statistical distributions for each of the input parameters were established. The probability of failure was calculated, for each limit state using a range of plate thicknesses, frame spacings and annual numbers of impacts, using First Onler Reliability Method software. The probability of failure was approximated as a plane for each limit state and frame spacing. -- Plate thickness was optimised for minimum cost. Minimum safety levels for permanent set and membrane collapse were also specified. The objective function considered costs due to construction, aesthetics, repair and replacement. Cost due to lost use of the ship and increased weight can also be specified. These costs were considered to be specific to the vessel under consideration and hence, were considered outside the scope of the present analysis. Optimum plate thicknesses are presented and compared with those specified by the Proposals for the Revision of the Arctic Shipping ...