Joint Project:

UnderwaterINSPECT – Technologies for the reliable and efficient Testing of Underwater-Foundations at Offshore Wind Turbines


Structural Stability of Offshore Foundations and System Integration


2012-11-01 / 2015-10-31


Within the framework of the Call TIMM – Technologies for Offshore Inspections and Monitoring, the Federal Ministry for Economic Affairs and Energy in cooperation with Projekttraeger Juelich (PTJ) are financing the R&D project UnderwaterINSPECT.

In particular, offshore foundation structures are exposed to high loads, due to the complex superposition of cyclical and stochastic dynamic loads caused by the impact of wind, waves and the constant operation of the offshore wind turbine, all of them affecting the global structural stability and possibly causing local cracks of the weld seams, finally resulting in the possible failure of the foundation structure.

The sub-project “Structural Stability of Offshore Foundations and System Integration” deals with the development of solutions for the monitoring of the global structural stability, with three large-scale experiments crucial for the development, testing and – above all – for the practical applicability of the new methodologies and technology to be developed:

    • Laboratory tests for the development of methods, sensor and electronic systems and for the improvement of the systems for underwater application.
    • Large-scale test in the pilot plant using a large-scale monopile in the Fraunhofer IWES foundation test pit filled with sand and water. A fatigue test applying cyclical loads as usual with offshore wind turbines is carried out and accompanied by measurement. The test aims at the measurement of soil-structure-interactions and at the detection of damage.
    • Practical tests offshore: For the monitoring of the structural stability and verification of weld seam cracks Baltic Taucher will install the full system at an appropriate offshore structure and test the system in a real offshore structure under real operating conditions. The associate partner EnBW provides access to a structure suitable for our testing purposes.



      • Wölfel Engineering GmbH + Co. KG


      • Baltic Taucherei- und Bergungsbetrieb GmbH, Rostock
      • Fraunhofer-Institut für Keramische Prüfsysteme Dresden, FhG IKTS
      • Fraunhofer-Institut für Windenergie und Energiesystemtechnik Hannover, FhG IWES
      • Schweißtechnische Lehr- und Versuchsanstalt Mecklenburg-Vorpommern GmbH, SLV MV

      Funding details

      Project management agency

      • Projektträger Jülich, Standort Berlin, Schifffahrt und Meerestechnik

      Resulting service

      For Wölfel, the project UnderwaterINSPECT was the “door opener” for a new business field, namely the monitoring of the foundation structures of offshore wind turbines. This new business activity is based on the self-developed methods and algorithms of signal analysis and pattern recognition which were further enhanced for the monitoring of the stability of offshore foundations. In addition, the entire equipment from sensors to data transmission systems was selected and tested for the application in maritime environments.

      Today, Wölfel offers monitoring systems as well as monitoring services for offshore wind farms.

      Extract of references

      • RWE Innogy, Fundamentüberwachung WP Nordsee-Ost
      • Iberdola Renovables Offshore Germany, Foundation Monitoring Wind Farm Wikinger
      • E.ON, Amrumbank West
      • EWE, Alpha Ventus, Concept study for SHM
      • TenneT, Helwin 1, Concept study


      • Friedmann, H.; Eppler, J.; Kohlmeier, M.; Weihnacht, B.; Winkel, G.: UnderwaterINSPECT – Technologien zur zuverlässigen und effizienten Prüfung von Unterwasser-Tragstrukturen an Offshore-Windenergieanlagen, presentation at status conference Maritime Technologien, Rostock, 10.12.2015, proceedings of status conference 2015, S. 97-112, Jülich 2015, (=Schriftenreihe Projektträger Jülich)
      • Friedmann, H.; Kraemer, P.; Kohlmeier, M.: Entwicklung eines Structural Health Monitoring Systems für Gründungsstrukturen von Offshore Windenergieanlagen – Großversuch zur Ermittlung messtechnischer Grundlagen, presentation in Braunschweig on 18.03.2016, in : J. Stahlmann (Hrsg.): Messen in der Geotechnik 2016, S. 309 – 323
      • Spill, S.; Kohlmeier, M.; Kraemer, P.; Friedmann, H.: Messtechnische und numerische Untersuchungen an einvibrierten, lateral beanspruchten Stahlrohrpfählen, presentation in Braunschweig on 18.03.2016, in : J. Stahlmann (Hrsg.): Messen in der Geotechnik 2016, S. 291 – 308
      • Kraemer, P.; Friedmann, H.: Vibration-based structural health monitoring for offshore wind turbines – Experimental validation of stochastic subspace algorithms, in: Wind and Structures, Vol. 21, No. 6 (2015), S. 693-707 ; DOI : dx.doi.org/10.12989/was.2015.21.6.693
      • Friedmann, H.; Kraemer, P.; Ebert, C.: Vibration based structural Health Monitoring  (SHM) for Offshore Wind Turbines – From Monitoring the blades to a concept for Foundation Structures, presentation on 4. September in Hannover at IWEC 2014, as pdf available on proceedings disc

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