Author(s): John R. Kreider
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Keywords: No Keywords
Abstract: Impact loads during the summer from large, storm-driven multiyear flocs are an important consideration for gravity structures in the Beaufort Sea. This paper describes a numerical, time-domain solution for floe impact force in which the predominant ice failure mode is crushing. As the floe is crushed during impact, floe velocity decreases and contact area increases. As a result, parameters in the crushing equation vary with time. Pressure and force are non-linear with time or penetration. If the force exceeds foundation resistance, the structure may begin to slide causing additional non-linear effects. The model uses a Runge-Kutta technique to solve the one-dimensional equations of motion for the floe and the structure. The solution method is efficient compared to finite-element techniques and includes non-linear effects often ignored in simpler approaches. The paper describes model components and assumptions. Time histories of force, penetration, and velocity are presented for typical impacts. Predicted peak leads are presented for a range of floe diameters, floe velocities, floc thicknesses, and structure diameters. The influence of uniaxial crushing strength versus strain rate and brittle failure are described. The effect of foundation resistance on peak force is described by modeling the soil as rigid-perfectly plastic and allowing the structure to move if ultimate resistance is exceeded. The paper describes applications to summer multiyear floe impacts in the Beaufort Sea although the model could easily be adapted to other cases of interest, such as iceberg impacts or wave-driven impacts of first-year ice floes.
Year: 1984