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Post-Yield Strength of Icebreaking Ship Structural Members.

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Final rept.,

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The proposed ASPPR regulations allow a certain amount of plastic deformation of tile structure under extreme ice loads. The buckling criteria employed in the regulations has factors to take into account some of the nonlinear effects associated with exceeding the linear range of material properties. This project is an exploratory investigation into tile post-yield behaviour of icebreaking vessels with tile underlying objective to determine whether or not tile regulations are adequate in regards to buckling. The project consists of modelling two areas of the MV Arctic under a ASPPR calculated ice load of total magnitude F. The main frames were redesigned locally to conform to the proposed ASPPR regulations. An analysis was performed using the finite element program ADINA and consisted of a nonlinear static analysis using the arc-length method load-displacement control. Plasticity was found to initiate in the main frames at a load of about .7F. Buckling was found to occur in the main frames at a load level of approximately 1.2 F sub max. The load requirad to cause buckling calculated using linear assumptions was significantly higher indicating a substantial degradation of buckling strength associated with tile progression of yielding through tile structure. The structure was found to be capable of carrying further load through membrane strength in the plating. The analysis accounts for global ship effects in the local area by modelling the entire MV Arctic using the program MAESTRO. Conclusions were drawn as to how the global effects can be included in the local mode without the requirement of modelling the entire ship. MM

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  • Marine Engineering

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