The action of short multi-year ridges on upward sloping conical structures

Abstract

Multi-year (MY) ridges often control the design ice loads on Arctic structures. Ice loads due to MY ridges on sloping structures vary with whether the ridge is long or short. This paper addresses short ridges. A parallel paper addresses long ridges. For short ridges, critical lengths for loads are usually when they are shorter than their characteristic length; in particular, when no hinge cracks occur. In this situation, loads in prior methods were dominated by ride up forces. New methods have been developed which include two load relieving mechanisms. These are 1) failure across the ridge width as it rides-up and 2) a limit to ride-up based on downward failure of the pushing ice sheet. These limit mechanisms can lead to lower loads than in prior methods and usually result in loads from short ridges being lower than for long ridges of the same cross section and strength. Nevertheless, in any comprehensive load approach the engineer may wish to check loads from both long and short ridges. In fact this is necessary in probabilistic methods into which these new algorithms have been incorporated.The new methods for short ridges result in a relatively simple set of equations and these are provided in the paper. The equations have been incorporated into spreadsheets and example inputs and outputs are given.