# Recent Advancement in Assessment and Control of Structures under Multi-Hazard
## 6 Multi-Hazard Assessment and Control of Wind Turbines
### Multi-Hazard Vibration Control of Wind Turbines  
Vibration control of wind turbine structures, subjected to the combined actions of wind, waves, and earthquake ground motions, is extensively reported in the literature. These studies are mostly aimed at the optimization and performance assessment of control systems. A summary of relevant studies on the vibration control of wind turbine structures subjected to multi-hazard is presented in Table 3.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Reference** & **Hazard** & **Structure** & **Control System** & **Main Contribution/Conclusion** \\ \hline [PERSON] et al. [163] & Wind and Waves & Offshore, 5 MW, barge-type floating & TMD on the platform & Modelling of drivetrain dynamics, optimization of TMD parameters, simulation results confirm the importance of drivetrain dynamics and that TMDs are effective in vibration suppression \\ \hline [PERSON] et al. [164] & Wind and Waves & Offshore, 5 MW, barge-type floating & TMD in the nacelle & TMDs are effective in reducing standard deviation of tower-top displacements, with upto 50\% reduction for TMD mass ratio of 2\% \\ \hline [PERSON] and [PERSON] [165] & Wind and Waves & Offshore, 5 MW, monopile & TMD in the nacelle & Misalignment of wind and wave load significantly increases base moment in the side-side direction, which can be reduced by 40\% with a TMD \\ \hline [PERSON] et al. [166] & Wind, wave and seismic & Offshore, scaled model, monopile & TMD in the nacelle & Shake table tests for modal identification and estimation of aerodynamic damping, results show that TMDs are effective in reducing seismic response, effectiveness increases with rotation speed of blades \\ \hline [PERSON] and [PERSON] [167] & Misaligned wind-wave and seismic & Offshore, 5 MW, monopile & Pendulum tuned TMD(PTMD) in the nacelle & PTMDs are slightly more effective than two linear TMDs with equivalent mass and their stroke is smaller \\ \hline [PERSON] and [PERSON] [168] & Misaligned wind-wave & Offshore, 5 MW, monopile & PTMD in the nacelle & Increase in fatigue life due to PTMD is 50\% higher than that due to dual linear TMDs. \\ \hline [PERSON] et al. [169] & Misaligned wind-wave and Seismic load & Offshore, 5 MW, monopile & PTMD in the nacelle & PTMD is more robust than dual linear TMDs, and with a mass ratio of 2\% reduction in short-term fatigue damage is reduced by up to 90\%. \\ \hline [PERSON] et al. [170] & Wind and waves & Offshore, 5 MW, barge-type floating & Tune Mass Damper Inerter (TMDI) in the nacelle & ThML are more effective than TMD but there is a trade-off between fore-aft load control and device stroke; performance superior to TMD can be achieved for comparable device stroke \\ \hline [PERSON] et al. [171] & Wind and Waves & Offshore, 5 MW, monopile & MTMD & MTMD \\ [PERSON] et al. [172] & Wind, Waves and Earthquake & Offshore, 5 MW, monopile & MTMD & Multi-mode control using MTMDs are more efficient than STMDs in multi-hazard scenarios \\ \hline [PERSON] et al. [173] & Wind, Waves and Earthquake & Offshore 5 MW with standard jacket foundation & MTMD & SSI plays important role in MTMD performance, often over-estimates it \\ \hline [PERSON] et al. [174] & Wind and Earthquake & Onshore 5 MW & TMD and Tuned Liquid Column & Resonant tower vibrations at lower wind speeds are effectively reduced by TMDs and TLCDs, transient tower vibrations at higher wind speeds are less effectively reduced, only nominal control of seismic-induced vibrations \\ \hline [PERSON] and [PERSON] [175] & Wind and Waves & Offshore, monopile & TLCD & TLCDs are effective in reducing peak response and increasing fatigue life \\ \hline [PERSON] et al. [176] & Wind and Waves & Offshore, 5 MW, jacket type & Tuned Liquid Column Gas Dampers (TLCGD) & Effective in reducing nacelle \\ \hline \hline \end{tabular}
\end{table}
Table 3: A summary of published works on vibration control of wind turbine structures subjected to multi-hazard.