Strong tower vibrations may occur during the installation of wind turbines, often caused by wind or wave excitation. As turbines are becoming ever larger, the first structural natural frequency may be in a range as low as 0.12 Hz to 0.2 Hz. Periodic wave excitation is probable to occur in the same frequency range. Wind-induced lateral excitation due to vortex shedding may also occur at these low frequencies, depending on the wind speed and the shape of the tower. Both may lead to resonant vibrations when the structure’s natural frequency and excitation frequency match. For wind turbines during installation structural damping is low and small excitation forces may already lead to large vibration amplitudes. The resulting challenges can be solved by temporary tuned mass dampers.
When large vibration amplitudes occur during installation, they often lead to a high lifetime consumption. Temporary tuned mass dampers help to considerably reduce fatigue loads and make it possible to install turbines in a larger range of wave and wind conditions. This optimizes installation scheduling and reduces costs.