phase 4 report - DNV

RN02: DESIGN OF FLOATING STRUCTURES IN ICE // PART 4 ANNEX ABarents 2020A.13 Floating structuresA.13.4 ActionsThere are two types of probabilistic approach for ice actions on stationary floating structures, as follows:––Probabilistic calculations of ice actions for (linearized) system and specificinteraction scenarios (such as head on for ship-shape structure). The operationaleffect of ice management can be incorporated in such analysis.––Response based design (RBD), which involves long-term time domain simulations. Theoperational effect of ice management can be incorporated in such analysis.A.13.5 Hull integrityA.13.5.5 Condition monitoringTable A.13-N – Overview of possible structural monitoring systemsStructural monitoringVessel displacements/velocities/accelerationsLocal ice pressureMooring line tensionCommon methodologyGyrocompassPressure panelsStrain gauges / Tension boltsA.16 Other ice engineering topicsA.16.5 Ice tank modellingA.16.5.1 GeneralIce tank modelling can be used to investigate various ice-structure interactions and offers the advantage thatrelatively complex problems (that can be difficult to analyse using other methods) can be studied and visualized ata small scale (i.e. smaller than full scale).Generally, ice model tests have been used to investigate global ice actions resulting from moving ice, such as theexpected ice actions and/or the expected ice interaction modes (e.g. ice failure modes, ice ride-up, the build-upof ice rubble around a structure, ice clearing behaviour around a structure, ice blockage, etc.). Ice model testshave not been used to investigate static ice actions, e.g. resulting from thermal effects. Also, ice model tests havegenerally not been used to investigate local effects, such as local ice pressures.The results of the ice model tests can be used for calibration and verification of numerical models that have beendeveloped for investigation of the floating structure/ice interaction. In this case, additional requirements to the icemodel tests are typically made (e.g., boundary conditions should be determined during the ice model tests).Clear specification of the objective of the ice basin model tests is useful in order to avoid setting up tests that onlygive partial answers to the questions raised. The objectives could be one or more of the following, but not belimited to these:––Determine global ice actions on the structure in fixed configuration––Determine forces on mooring or requirements to station-keeping––Determine the ability to ship-shaped floating structures to vane in various ice conditions––Provide validation data for model calculations or other means of obtaining ice actions––Qualitatively study the behaviour of the floating structure, e.g. accelerations, offsets etc––Investigate the effects of managed ice on the floating structure and its station-keeping system––Investigate ice clearance around the structure and under hull ice transport––Study different ice breaking hull shapes with the aim to recommend one––Provide input to evaluate fatigue life under ice actions.––Provide insight to the ice failure modeBefore embarking on ice basin model tests it is normal to assess the extent to which the questions raised can bereliably investigated by the tests.Report no 2012-0690 91