Bohai Sea Ice Cone Ice Load

Offshore structures located in ice infested area need to resist static and dynamic ice force. It is known that most jacket platforms are designed as vertical legs so that ice failures in crushing during ice interacting with the structures. At 1970's it was proposed that adding ice-breaking cones could significantly reduce ice force and comprehensive theoretical and laboratory tests have conducted on this subjects since then. But we still have no definite answer on this question. It is necessary to evaluate effect of ice-breaking cone by full-scale tests. Otherwise, only few researchers discussed the dynamic ice forces of conical structure.Based on full-scale tests conducted on offshore jacket platforms. The previous researches of ice forces of conical structures are summarized first. It is found for the compliant structures installing ice-breaking cones dynamic ice forces could not be neglected, as ice-breaking frequency could equal to the natural frequency of the structure. It is also found that the static force could be determined through the test data. The whole work is generalized as below:(1) Video analysis- The video analysis is approached in two aspects. Firstly, to give the gist of the theory analysis by observing the failure modes of ice-structure interaction; Secondly, taking ice breaking period, ice breaking length, ice thickness and ice velocity by watching video and local observation.(2) Response analysis- During calculating the data of response of the structure, investigate the vibration amplify phenomenon in detail, and get the displacement amplitude distribution by using the theory of Stat.(3) Ice load panel analysis- Using the ice load panel, we obtain the real ice force in partial, and then calculate the whole ice force of the structure combined with the response analysis, furthermore, we also obtain the ice force amplitude distribution, ice-structure impact time, ice frequency and so on.(4) Through these work above, colligate the static ice force researches, establish the dynamic ice load function of the conical structure.The research of the ice induced vibrations with conical structures is a very complex and systemic procedure. There are many other work need to be done such as the frequence analysis of ice force and structure respondence, and the form of the ice load function is still need to be improved because the angle and diameter of cone, the ice thickness and velocity can not be ignored at all.