Principles for Local and Global Ice Design Using Pressure-Area Relationships

Abstract

The design of offshore structures for ice loads requires estimates of global ice forces and local ice pressures on the structure. The focus is ice crushing against a structure, for example icebergs impacting an offshore rig. To determine these, the global interaction area and local design area are precisely defined. A rational basis for defining these physical areas of concern in the interaction of ice masses with offshore structures is presented. If data are analyzed correctly in accordance with these definitions, design relationships can be developed. Two separate relationships are presented, one for global pressures and the other for local pressures. Data from all sources demonstrate a decrease of average pressure, local or global, with increasing area. The inclusion of number and duration of interactions is an important aspect. The present formulation is suitable for limiting kinetic energy situations but further analysis of data is needed for global pressures that persist for periods of time.