Diss. Helsingfors : Sjöfartsverket, 1978

The replacement of conventional massive lighthouses with slender steel lighthouses or buoys with piers entails pronounced vibrational problems during ice loading. In the present study the interaction of a moving ice sheet with, slender bottom founded pile structures 'is studied in a continuous crushing mode. A mathematical model is formulated by connecting the properties of ice to the dynamic equations of motion of structure through an averaged ice crushing strength curve. The resulting group of differential equations is autonomous and hence ice-induced vibrations in the structure will be self-excited by nature. The conditions under which vibrations - dynamic instability - are aroused are solved rigorously and approximatively for practical purposes. Limit cycles and their frequencies are solved by numerical integration. The overall capability of the created model is verified by comparing the calculated results of three application structures with those measured and observed in-situ. With the presented model it will be possible to design structures which are more secure against dynamic ice loads. The qualitative effects of the most important parameters in ice and structure interaction are, given. Quantitative results are trend-giving and require more accurate measured ice crushing strength curves. Total damping is observed to be the most paramount of the too little known parameters affecting limit cycles. A comparison of the predicted and measured force plots suggests that ice-induced damping during crushing is considerably greater than pure structural damping.