ABSTRACT
Ice-Mas is a simulator used for design of offshore structures interacting with ice combining a variety of models and approaches. It was initiated by TechnipFMC with a joint-cooperation with Cervval and Bureau Veritas.
This paper present overall functionalities of Ice-Mas. It will then focus on the modelling approach used for a semi-submersible platform, the calculation of the different ice load and ‘shielding effect’ according to the ice incidence angle. The time series of load will be applied to moored submersible to calculate the motion response and tension force. The result can be used as a reference for design of semi-submersible.
In the Arctic ocean, significant part of resources remains to be recovered especially in deep-water area. For further exploitation in Arctic area, the design of floating units is necessary.
The design of floating structure in ice covered ocean faces a number of challenges due to complex phenomenon of ice failure and interaction with structures. The interaction between a structure and sea ice is a complex process. Ice failure caused by interacting with offshore structure has been investigated by many scientists using analytical and empirical techniques and numerical methods (FEM, DEM, CEM, etc). T.D.Ralston (1980) proposed the plastic limit analysis method to investigate the forces imposed on conical-shaped structures by moving ice sheets. D.E.Nevel (1992) obtained the analytical solutions for the failure of an infinite ice wedge beam on an elastic foundation. The solution then finds application in the calculations of ice breaking loads for various types of sloping structure. Lubbad and Løset (2011). and Konuk, Gürtner et al. (2009) combing different numerical models to predict the ice failure due to the interaction between sea ice and structures. These methods mentioned above are widely used in modelling ice behavior and calculating ice loads exerted on structures in ice covered ocean.
However, failure modes of ice can be quite different depending on the shape of structure, ice type, ice thickness and interaction velocity etc.. Even with methods mentioned above, the prediction of ice loads is still a challenge. Especially in the case of semi-submersible units, the geometry of the interacting structure with ice is widely variable. The number of columns and the intruding angle of ice sheet and also size and depth of the pontoon are important parameters in the calculations. The broken ice from ice sheet will accumulate around the legs and contributes a non-negligible part of ice load on structure. This force is also affected by parameters mentioned above.
