Eccentric impact of an ice feature: linearized model

Abstract

Eccentric impacts of an ice feature against a floating or stationary offshore structure or ship are much more likely than a head-on collision. Both numerical models and analytical evaluations have demonstrated that eccentricity of impact leads to a significant decrease in the maximum ice load as compared to a head-on collision. This fact should have a great influence on the definition of the design ice load for structures subjected to impacts with moderately sized floating ice features. The present paper deals with a relatively simple model of ice-structure interaction which describes an ice feature motion in a horizontal plane (three-degrees-of-freedom model). The instant reaction force (i.e. ice failure load) is assumed to be directly proportional to indentation depth. In spite of simplicity of the model, analytical expressions for reduction in ice force due to eccentricity obtained seem to be valid for more general situations. It is shown that the relative reduction in the maximum reaction force due to impact eccentricity does not depend on the effective stiffness of contact. The influence of the frictional force on the maximum ice load has been considered as well. As it follows from the analysis of linearized model of interaction, the reduction coefficient does not change dramatically if frictional effects are taken into account. The general conclusions and results are readily illustrated by the example of interaction between homogeneous elliptical cylinder and rigid wall.