Validated model based development of damage index for Structural Health Monitoring of offshore wind turbine support structures

This paper investigates the structural monitoring concept and data analysis strategy using an example of an operating offshore wind turbine in the North Sea. As part of the data evaluation strategy; a design verification is shown for the bending moments calculated from monitoring data, operational modal analysis is performed to identify the first three dominant natural frequencies. Then an FE Model is prepared and validated with the identified natural frequencies so that, the model fairly represents the as built healthy physical structure. Finally, variation of the natural frequencies are traced for increasing sea bed scouring (change in boundary condition). This study is done to make up for the absence of such monitored events and as part of the introduced data evaluation strategy to initiate thresholds for damage sensitive global parameters. (C) 2017 The Authors. Published by Elsevier Ltd.