Ice force is the dominant external force on structures constructed in the sea covered with ice floes. In this study we clarified the wind and current forces acting on ice floes. " We obtained the drag and friction coefficients of wind and current respectively by changing the sizes and thicknesses of model ice floes systematically and proved they approximate to figures obtained by field researches. In addition, we developed a formula for drifting velocity and verified that the calculation results applied to the coefficients described above approximate to the field research results.

1. Introduction

Ice force is one of the important dominant external forces which have to be given consideration in designing structures in water areas where the surface is covered with ice or which are frozen. The ice force here means the fluid force which is produced by wind and current acting on floating ice floes and then on the structures touching it. The fluid force acting on floating ice floes is also called the environmental force because the environment surrounding the ice floes produces the, actual force acting on it. The force is mainly classified into four types, (I) the shear force caused by the friction between the wind and the surface of the ice floes, (2) the form drag produced by the wind blowing against the part of the ice floes above the sea surface, (3) the shear force caused by the friction between the water and the underside of the ice floes and (4) the form drag produced by the current hitting the ice floes under the sea (Fig. I). However large the fluid force acting on ice floes, the maximum ice force acting on structures is never larger than the ice force occurring when the ice floes is broken.

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