Loraux Christophe

Duration : 01.10.2013 – 31.12.2017
Supervisor : Professor Eugen Brühwiler
PhD student : Christophe Loraux

Long term monitoring of existing wind turbines towers and fatigue resistance of UHPFRC under compressive stresses

This project aims to provide solutions to increase the service duration of Wind Turbines, currently limited to 20 years. Two lines of research are explored. The first focuses on the realistic examination of the fatigue life of existing Wind Turbines using data from a long term monitoring. The second explore the fatigue resistance of Ultra High Performance Fiber Reinforced Cement-based Concrete (UHPFRC) under compressive stresses, for a future application in precast Wind Turbine towers.
An existing Wind Turbine tower is instrumented using strain gauges and temperature sensors. This allowed to precisely and continuously measure the wind loads and fatigue loads acting on the Wind Turbine. A method combining monitored data and meteorological and operational data provides a safe estimation of the remaining service duration of the tower. Results from the measurement campaign clearly demonstrate that Wind Turbine towers can safely be extended beyond 20 years using the simple, robust and economic monitoring system developed in this project.
In parallel, compressive static and compressive fatigue tests are carried out on thin UHPFRC plates (450mm high, 100mm wide and 30mm thick) in order to understand the fatigue behaviour of UHPFRC under compression loads. UHPFRC exhibits a very high resistance in compression, up to 200 MPa. Fatigue tests are performed at a very high number of cycles (up to 20 million cycles!) and showed an incredible behaviour of UHPFRC in fatigue in compression. The use of UHPFRC for the construction of high Wind Turbines towers have the potential to achieve a more sustainable and economic wind turbines of the next generation.