Study on the Fuzziness in Fatigue Life Estimation of the Foundation of Offshore Wind Turbine
Ignoring the influence of the load sequence and the damage caused under low-stress level are two mail shortcomings of traditional fatigue life estimation method based on the Miner theory. Fuzzy method for fatigue analysis of the foundation of offshore wind turbine is investigated. A fuzzy accumulative damage model is founded and used for fatigue life analysis of a tripod foundation. The fatigue damage is calculated using the traditional certainty method and the present fuzzy method. A tripod foundation under single-level and multi-level fatigue loads is used as the test structure. And the load sequence is considered. The calculation results of stress level are used with three forms, named the increasing mode, the to-and-fro mode and the sine mode, for structure fatigue life analysis. It reveals that the load sequence and low-stress level play an important part in the fatigue analysis and should not be ignored. The anti-fatigue character of the structure under a group of increasing loads is better than the structure under a group of decreasing loads; and it is called the forging effect. The present fuzzy accumulative damage model is more accurate and reasonable than the traditional certainty method.
Chaohe Chen, Yong Huang and Guangfan Li
W. Li "Study on the Fuzziness in Fatigue Life Estimation of the Foundation of Offshore Wind Turbine", Advanced Materials Research, Vols. 243-249, pp. 4741-4745, 2011