Author(s): Mauri Maattanen
Linked Author(s): Mauri Määttänen
Keywords: No Keywords
Abstract: Dynamic ice-structure interaction model tests with a vertical pile in continuous crushing mode were carried out at U. S. Army CRREL Ice Engineering Facility. Outline of test arrangements and procedures is given. A lot of data was gathered on interaction modes, ice forces, vibrational behavior and damping. Analysis of results showed that at low velocities a saw-tooth like ice force and displacement pattern is dominant and that crushing frequency is directly proportional to ice velocity and inversely proportional to ice force. With increasing velocities dynamically unstable modes locked the crushing frequency in themselves and the increase of velocity appeared in the increase of response amplitudes which got their maximum at resonance velocities. If resonance velocity was exceeded a shift to next natural mode occurred or crushing became random. Locking to stable natural mode never occurred. The true interactive ice force decreased with increasing velocity but deflection amplitudes increased as long as resonance velocity was not exceeded. Pile deflection rate became easily so high that it made ductile ice loading rate possible even at otherwise brittle loading rates. Maximum recorded ice force values were mostly at low velocities but appeared also randomly at all the testing velocity ranges. During crushing, both positive and negative ice-induced damping appeared. Locally, negative damping could be overcritical but the equivalent effect was of the same order as the effect of ice-induced positive damping. Measurement data verify that the theory of self-excited vibrations is valid in predicting dynamic ice-structure interaction.
Year: 1981