TOWARDS STRUCTURAL HEALTH MONITORING BASED RISK BASED INSPECTION PLANNING FOR OFFSHORE WIND TURBINE SUPPORT STRUCTURES

摘要

Almost all offshore wind farms across the world are equipped with a Structural Health Monitoring (SHM) system. Nevertheless, the benefit of using data analysis results for Operation and Maintenance (O&M) optimization is not yet effectively exploited. Reasons for this are manifold but dominated by the fact that usually the development of the SHM system is not integrated from the beginning as part of the project management process. Rather, in most cases, it is mainly implemented to fulfill the minimum requirements by relevant authorities. In addition to this, as the use of monitoring data for possible life time extension is well established, stakeholders miss the benefits for young age wind turbines. However, current research has shown that SHM results are also useful in the early life cycle range to determine healthy state reference parameters and also to optimize the variation of the as-built structure from the designed structure. The information obtained from an SHM system therefore is an added value, which can be estimated before implementing it using value of information concept.The main purpose of implementing an SHM system is to reduce uncertainty. This paper makes use of SHM data analysis to reduce the uncertainty of stress ranges when performing reliability analysis for Risk Based Inspection (RBI) planning. For this study, one year strain time history data from four monitored wind turbines in an offshore wind farm in the North Sea is used. The measured stress cycles are counted by Rain Flow Counting (RFC) and grouped into stress range bins. Finally, the distribution of the counted stress cycles are used to fit a Weibull probability distribution function to estimate the parameters and compare them with recommendations from literature and standards. This way, an individual RBI planning for the monitored offshore wind turbines is enabled.