Ice Loads And Ice Vibration Platform Fatigue Analysis Method

Ice load is the most preponderant factor to the working offshore platform in ice region. Ice induced vibrations will result in structural damage to any extent. The higher level of maximum ice load will even completely push over the structure in a short time. Hot spots stresses produced by alternating dynamic ice force evidently result in the partial fatigue failure. All these facts account for the importance of ice load research.First this paper summarized the past research related with ice load during the crushing interaction between sea ice and structure, and introduced the in-situ full-scale structural measurement system on JZ20-2 and JZ9-3 platform in Bohai Liaodong gulf and working principle of ice load sensing panel. This dissertation investigated the several failure modes, such as ice plastic failure on the course of" slow indentation, crack damage failure of middle ice velocity, and ice brittle failure of fast ice velocity. Attention is placed on the analysis of ice load being produced in ice plastic failure according to ice of different thickness. After comparing this result with commonly accepted formula this dissertation found that modified coefficient a should be adjusted in order to decrease the design risk of offshore structure suffered by ice load in cold ice region. Secondly this dissertation made the statistical analysis of brittle ice load, and results showed that there was a greater variance of ice load during slow ice speed movement and a smaller variance of ice load during fast ice speed movement. What's more, when ice speed varies from slow value to high value, the appearance of maximum ice loads on different locations changes from synchronization to randomness.Finally, according to the working environment characteristics of offshore platform interacted with random ice force in ice region, this dissertation proposed power spectrum method to analyze the fatigue life of platform. According to the different failure modes, equivalent fatigue stress breadth method was suggested to use in the fatigue damage analysis.