Offshore Structural Health Monitoring: Concept of a Global Monitoring System Based on the Structure Dynamic Behaviour

Introduction

The foundation structures of offshore wind turbines and converter stations are ‘new’ structures:
- The database for design loads is small
- This results in high partial safety factors
- The load bearing characteristics of the subsea soil is complex
- the structures have large dimensions

Monitoring of offshore wind turbines or transformer stations decreases the uncertainties involved with ‘new’ structures.

The main aims are:
- meeting regulatory or third party requirements
- life time prolongation
- complementation of periodic inspections
- assessment of structure condition and safety
- life cycle management

Especially the assessment of structure components under water is a challenge for the wind industry and permanent monitoring systems help to reduce both the costs and the risks involved with ‘conventional’ structure inspections by divers.


Approach

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Main body of abstract

Most monitoring systems for offshore structures implemented in the past are ‘local’ monitoring systems which focus hotspots.

In contrast, we present the concept of a ‘global’ monitoring system based on ambient vibration monitoring techniques, which we implemented in five offshore wind farms already. Examples of different realizations will be given.


Conclusion

The advantages of the concept are:
- only few and reliable sensors are needed
- sensors can be placed in accessible positions to decrease maintenance costs
- the method focuses on loads and the load bearing characteristics of the structure



Learning objectives
- regulatory requirements
- standards regarding structural monitoring
- importance of defining monitoring aims
- different monitoring concepts and their advantages
- monitoring concepts in other industries
- what is necessary to use monitoring as a tool in asset management, especially in structure inspection concepts