phase 4 report - DNV

RN02: DESIGN OF FLOATING STRUCTURES IN ICE // PART 4 ANNEX ASince the volume of the sail is small compared to that of the keel, the effects of the ridge sail can be neglected inthe case of first-year ridges. The action component, F c, can be determined, as an estimate, using instructions givenin A.8.2.4.3 and A.8.2.4.3.3 for parameters of the consolidated layer of an ice ridge, or A.8.2.4.4 for slopingstructures by substituting h cfor w.Figure A.8-12 – Idealized geometry of a first-year ridgeSeveral models are available for the determination of the unconsolidated keel action component F k. Passive failuremodels are generally used to determine the unconsolidated keel action component acting on vertical or inclinedstructures. Measurements indicate that the keel cohesion often varies from zero at the base of the keel to amaximum immediately beneath the consolidated layer. Under such conditions, the keel action can be determinedfor vertical structures (see Reference [A.8-21]), with suitable modification (see Reference [A.8-22]) as given byEquations (A.8-49) and (A.8-50):Whereμ φφcwis the passive pressure coefficient;is the angle of internal friction;is the apparent keel cohesion (an average value over the keel volume should be used);is the width of the structure;γ eis the effective buoyancy, in units consistent with c.88RUSSIAN–NORWEGIAN COOPERATION PROJECT