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In this paper, the problem of wind-induced vibration in tall buildings is addressed by utilizing a new type of damper, the tuned mass damper fluid inerter (TMDFI). The TMDFI incorporates an inerter in the classical tuned mass damper (TMD), which is physically realized using fluid in a helical channel. The device arrangement is optimized using a proposed nonlinear procedure and it is demonstrated through numerical simulations that the application of the TMDFI achieves excellent vibration control performance. Specifically, it has been found that the TMDFI requires lower mass and stroke requirements than traditional passive dampers while achieving comparable or better vibration reductions. It has been shown numerically that the damper demonstrates excellent vibration control capabilities by reducing the RMS displacement of the building by ≈50% and the RMS acceleration by 35%–80%. The results presented here show that the TMDFI is a damper capable of mitigating wind-induced vibrations in tall buildings with relatively simple design requirements. This new damper has the potential to significantly improve the safety, comfort, and durability of tall buildings subjected to wind loads. [ABSTRACT FROM AUTHOR]

Bearing failure in wind turbine gearboxes is one of the significant sources of downtime. While it is well‐known that bearing failures cause the largest downtime, the failure cause(s) is often elusive. The bearings are designed to satisfy their rolling contact fatigue (RCF) life. However, they often undergo sudden and rapid failure within a few years of operation. It is well‐known that these premature failures are attributed to surface damages such as white surface flaking (WSF), white etching cracks (WECs) and axial cracks. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper. The risk associated with TTRs motivates the need to mitigate TTRs arising in the drivetrain due to various transient events. This paper investigates three TTR mitigation methods. First, two existing devices, namely, the torsional tuned mass damper and the asymmetric torque limiter, are studied to demonstrate their TTR mitigation capabilities. Then, a novel idea of open‐loop high‐speed shaft mechanical brake control is proposed. The results presented here show that while the torsional tuned mass damper and the asymmetric torque limiter can improve the torsional vibration characteristics of the drivetrain, they cannot mitigate TTRs in terms of eliminating the bearing slip risk associated with TTRs. However, the novel approach proposed here can mitigate TTRs both in terms of improving the torque characteristic in the high‐speed shaft and reducing the risk of bearing slip by actuating the high‐speed shaft brake at the onset of the transient event. Furthermore, the control method is capable of mitigating TTRs with the mechanical limitations of a pneumatic actuator in terms of bandwidth and initial dead time applied to it. This novel approach allows the wind turbines to protect the gearbox bearings from TTRs using the existing hardware on the turbine. [ABSTRACT FROM AUTHOR]

This paper proposes the use of a tuned mass damper fluid-inerter (TMDFI) for vibration control of spar-type floating offshore wind turbine towers. The use of an inerter in parallel with the spring and damper of a tuned mass damper (TMD) is a relatively new concept. The ideal inerter has a mass amplification effect on the classical TMD leading to greater vibration control capabilities. Previous work by the authors has shown that inerter based TMDs have great potential in vibration control of floating offshore wind turbines where enhanced vibration mitigation can be achieved using a relatively lighter device than classical TMDs. However, this previous work was based on the assumption of an ideal inerter that assumes the use of a mechanical flywheel type inerter. Mechanical inerters have some inherent disadvantages due to their complexity in design and high cost of maintenance. The use of a fluid inerter can alleviate these disadvantages as its design is rather simple and it comes with very low maintenance. Such devices have been proposed and investigated in the literature, however, their applicability in vibration control of floating wind turbines has not been investigated by researchers. The optimal design of a TMDFI is presented in this paper. It has been shown that optimization of a TMDFI is a six-dimensional non-linear optimization problem whose solution hyperplane contains multiple local minima. A systematic way has been developed in this paper, avoiding the use of metaheuristic search techniques, to optimize the damper while providing greater insight into the damper properties that offers a set of guidance to the designer. Numerical results demonstrate impressive vibration control capabilities of this new device under various stochastic wind-wave loads. It has been shown that the fluid-inerter performs as well as the ideal mechanical inerter. The considerable advantages of a TMDFI over the classical TMD demonstrated in this paper makes it an exciting candidate for vibration control. • Proposed tuned mass-damper-fluid-inerter (TMDFI) for FOWT tower vibration control. • Developed approach of finding global minima of a 6D TMDFI optimization problem. • Provides insight into the properties and behaviour of the TMDFI for designers. • TMDFIs impressively control FOWT tower vibrations significantly better than TMDs. [ABSTRACT FROM AUTHOR]

Summary: This paper investigates the use of a passive tuned mass‐damper‐inerter (TMDI) for vibration control of spar‐type floating offshore wind turbine towers. The TMDI is a relatively new concept as a passive vibration control device. The configuration consists of an "inerter" attached to the tuned mass, parallel to the spring and damper of a classical tuned mass damper (TMD). The inerter provides a mass amplification effect on the classical TMD. The presence of the inerter virtually increases the mass of the damper leading to greater vibration control capabilities. This enables one to achieve improved vibration control using a lighter damper. Using a lightweight damper is particularly important for an offshore wind turbine because increasing mass on top of the tower can destabilize the overall system and increase tower vibrations, as demonstrated in this paper. The development of a passive TMDI for an offshore wind turbine tower has been proposed in detail in this work. Numerical simulations have been performed and results are presented demonstrating the impressive vibration control capabilities of this new device under various stochastic wind‐wave loads. It has been shown that the TMDI has considerable advantages over the classical TMD, achieving impressive response reductions with reductions in the stroke of the tuned mass. The TMDI has been shown to be a promising candidate for replacing the classical TMD for offshore wind applications. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) are the largest rotating structures on the earth. Dynamically sensitive structures such as these must be protected in these environments to ensure that they can continue to operate reliably and safely. In this paper structural dynamic models and probabilistic assessment tools are combined to demonstrate improvements in structural reliability when FOWT towers are equipped with a new type of damper — the tuned mass damper inerter (TMDI). A multi-body dynamic approach is used to model the wind turbine and the TMDI installed in the tower. The model is subjected to stochastically generated wind and wave loads of varying magnitudes to develop wind-induced probabilistic demand models for towers of FOWTs under model and load uncertainties. A focus is placed on the impact of the wind-wave misalignment on the lightly damped side-to-side mode. Numerical simulations are carried out to construct fragility curves which illustrate reductions in the vulnerability of FOWTs to wind and wave loading owing to the inclusion of the new damper. Results show that the TMDI delivers significant increases in structural reliability of FOWT towers. [ABSTRACT FROM AUTHOR]