Measurements from FORCE Technology provide Vattenfall Vindkraft (Vattenfall Windpower) with a realistic picture of offshore wind turbines that settle in the foundation.

Vattenfall Vindkraft A/S experiences that the transition piece between the monopile (foundation) and the wind turbine on their offshore turbines had settled due to failing concrete foundation, the so called grout (foundation). Therefore the wind turbine now rests on steel knees (brackets) that are not designed to carry the total weight of the wind turbine.

“We needed to know how large a part of the load that actually goes through the steel knees (brackets), what with the grout failing etc.” says Kasper Roed Jensen, Project Engineer, with Vattenfal Vindkraft. “FORCE Technology was able to examine tensions in the materials with strain gauges and determine their placement, and you have subsequently assisted in analysing measurements of the tension”, he continues.

Reality rather than models

“So far, our results show that the modelling we made ourselves is conservative at this stage of the failure, and therefore it is of great value to us that we can monitor the actual tensions continuously, and that we do not have to rely on models. This means that we have time to consider whether some of the foundations can be left for later inspection. We also realised that the solution is not unambiguous.

There may be various solutions due to difference in design of the steel knees (brackets) and the sizes of wind turbines in the various sites. In some locations we expect to have to repair and in others we can continue to measure and inspect”, says Kasper Roed Jensen.

Wide-ranging assistance

“Apart from measuring material stresses, we also make use of your expert advice on materials, testing and corrosion, e.g. microbial and sea water corrosion, and we use you as a provider of courses. It is obvious for us to use you as a Danish company as you have an established name in Denmark, and you are renowned for being technically sound”, concludes Kasper Roed Jensen from Vattenfall Vindkraft.