The forming cyclic loads on the offshore structures during ice field edge fracture
The non-stationary process of ice breaking at the contact of the edge of a drifting ice field (IF) and the sea ice-resistant platform (IRP) can lead to dangerous vibrations and potentially dangerous dynamic loads on this offshore structure. Extreme resonant oscillations of the platform base can cause not only violations of the regular functioning of the object, but also significantly reduce the reliability of the structure and its durability, causing fatigue fracture in the structure of the IRP or its equipment, also such process can change the bearing capacity of the soil under the platform foundation. Dynamic ice destruction is a complex process, and the development of models of this phenomenon requires a well defined methodology and research procedure. The dynamic reaction of the structure on impact of the ice field depends on a combination of many factors: the size and flexibility of the impacted leg of the platform; the ice loading velocity, temperature and physical-mechanical parameters of ice, and others. The object of this research is the physical processes involved in the real system "IF-IRP” - the energy transfer from the moving ice fields to the control volume of ice in the contact area, accumulates the elastic energy received to its critical level in this volume and causes its destruction with a certain frequency. The most important property of the object of study, i.e. the subject of the research, is the mechanism of ice fracture in the zone of interaction of two basic elements of the system: the ice field and IRP. The aim of the study is to identify and describe the regularities of formation of cyclic ice loads on the structureand describe the process, taking into account the phenomenological features of sea ice fracture as a mechanism for converting the kinetic energy of the ice field into the elastic energy spent on to deviations leg of the platform and the energy spent on destructing the ice.