Feasibility for Damage Identification in Offshore Wind Jacket Structures Through Numerical Modelling of Global Dynamics

摘要

Operational modal analysis is currently being researched to detect damages in offshore wind turbine structures. To make practical considerations, such as where to place sensors, it is valuable to know how different damages present themselves in the structural dynamics and what kind of damages can be detected given certain detectability limits. Through conducting natural frequency analysis, the modal response of a structure to damages are explored and resulting considerations for damage detection are discussed. A state of the art, detailed, numerical design model of the Wikinger jacket structure is used to investigate damage detection. Aspects of the model are changed to simulate damage, including member damage, scour, corrosion and more. The resulting modal parameters are calculated, these parameters are compared to those from an unaltered structure and metrics are calculated including frequency change, modal assurance criterion (MAC). It is found that when the frequencies of two modes intersect, there is a large change in the mode shape of the two modes from the undamaged case and the choice of which modes to compare between healthy and damaged can change the results significantly. The findings from each simulated damage are presented.