a b s t r a c tRecognized as one of the most mature renewable energy technologies, wind energy has been developing rapidly in recent years. Many countries have shown interest in utilizing wind power, but they are concerned about the environmental impacts of the wind farms. The continuous growth of the wind energy industry in many parts of the world, especially in some developing countries and ecologically vulnerable regions, necessitates a comprehensive understanding of wind farm induced environmental impacts. The environmental issues caused by wind farms were reviewed in this paper by summarizing existing studies. Available mitigation measures to minimize these adverse environmental impacts were discussed in this document. The intention of this paper is to provide state-of-the-art knowledge about environmental issues associated with wind energy development as well as strategies to mitigate environmental impacts to wind energy planners and developers.

Summary A particle tuned mass damper (PTMD), which is a creative integration of a traditional tuned mass damper and an efficient particle damper in the vibration control area, is proposed. This paper presents a comprehensive study that involves experimental, analytical, and computational approaches. The vibration control effects of a PTMD that is attached to a five‐story steel frame under seismic input are investigated by a series of shaking table tests. The influence of some parameters (auxiliary mass ratio, gap clearance, mass ratio of particles to the total auxiliary mass, frequency characteristics, and amplitude level of the input) is explored, and the performance of the PTMD with/without buffered material is compared. The experimental results show that the PTMD can achieve significant damping effects under seismic excitations, and the bandwidth of the suppression frequency is expanded, showing the device's robustness and control efficiency. In addition, an approximately analytical solution that is based on the concept of an equivalent single‐particle damper is presented, and the method to determine the corresponding system parameters is introduced. A comparative study between experimental and numerical results is conducted to verify the feasibility and accuracy of this analytical model. Copyright © 2016 John Wiley & Sons, Ltd.

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SummaryThe tuned liquid damper (TLD) and particle damper (PD) have been used as effective passive vibration absorbers to suppress undesirable structural vibrations induced by dynamic loads such as earthquake and strong winds. In this paper, through an integrated use of the TLD and PD, a new damper system named the tuned liquid particle damper (TLPD) was developed. The dynamic characteristics of TLPD in terms of tuning conditions and transfer functions were investigated through a series of shaking table tests. Nonlinear behaviors of TLPD in the frequency domain were discussed, and a preliminary framework was applied in the design of a five‐story steel frame building model using shaking table tests. Testing results confirmed the workability of the preliminary design framework as the primary structure is subjected to earthquake loadings. Performances of different TLPD‐structure systems were summarized from these testing programs. One of observations is that the TLPD system worked as a modified TLD in this study. The testing programs provide proof‐of‐concept results for this proposed vibration absorber.

analysis of a tall metal wind turbine support tower with realistic geometric imperfections. Earthquake Engineering and Structural Dynamics, 46(2), pp. 201-219. doi: 10.1002/eqe.2785 This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent AbstractThe global growth in wind energy suggests that wind farms will increasingly be deployed in seismically active regions, with large arrays of similarly-designed structures potentially at risk of simultaneous failure under a major earthquake. Wind turbine support towers are often constructed as thin-walled metal shell structures, wellknown for their imperfection sensitivity, and are susceptible to sudden buckling failure under compressive axial loading.This study presents a comprehensive analysis of the seismic response of a 1.5 MW wind turbine steel support tower modelled as a near-cylindrical shell structure with realistic axisymmetric weld depression imperfections. A selection of twenty representative earthquake ground motion records, ten 'near-fault' and ten 'far-field', was applied and the aggregate seismic response explored using lateral drifts and total plastic energy dissipation during the earthquake as structural demand parameters.The tower was found to exhibit high stiffness, though global collapse may occur soon after the elastic limit is exceeded through the development of a highly unstable plastic hinge under seismic excitations. Realistic imperfections were found to have a significant effect on the intensities of ground accelerations at which damage initiates and on the failure location, but only a small effect on the vibration properties and the response prior to damage. Including vertical accelerations similarly had a limited effect on the elastic response, but potentially shifts the location of the plastic hinge to a more slender and therefore weaker part of the tower. The aggregate response was found to be significantly more damaging under near-fault earthquakes with pulse-like effects and large vertical accelerations than far-field earthquakes without these aspects. KeywordsThin metal shell structure, imperfection sensitivity, seismic response, multiple stripe analysis, near-fault ground motions, vertical ground acceleration.

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Vibration-based damage identification has been widely studied in the field of structural health monitoring (SHM) for several decades. It is well known, however, that low-order modal parameters, being among the most frequently used, are not sensitive to local damage. A suitable methodology is therefore needed to extract such damage features from the dynamic response of structures. In the present work, local bending behavior of cables is studied for damage identification. First, the dynamic response of a cable is decomposed into evanescent wave and propagating wave components. It is proven that the contribution of the evanescent wave is spatially concentrated, and is sensitive to local damage. A signal transform is proposed next, which allows the estimation of the wave components from the measured cable response. The reflection coefficient of the evanescent wave (REW), which can be calculated from the estimated wave coefficients, depends only on the characteristics of the local discontinuity, and proves to be a robust indicator for local damage. The feasibility of the proposed methodology is studied by means of a simulated experiment, considering a cable model with two locally damaged parts. The results show that the intensity of REW is significantly higher near the damage locations, allowing damage localization. From the estimated REW near the damage locations, the damage levels can be estimated, showing the potential of this methodology for damage assessment of cable structures.

The main objective of this paper is to study the structural response and the failure modes of a typical wind turbine tower under different strong ground motions and wind loading based on a detailed finite element model of the tower. The ground motions were selected to match the design response spectrum with different design characteristic periods (Tg) in order to explore the influence of the frequency content of the earthquake on the response. The wind loads were generated from tropical cyclone scenarios. Nonlinear dynamic time-history analyses were conducted and the structural performance under wind load as well as short-and long-period ground motions was compared. A modal pushover was applied to further clarify the failure related to structural modes. It is observed that under strong wind loads the collapse of the wind turbine is driven by the formation of a plastic hinge at its bottom part, which is attributed to the contribution of the first (long-period) vibration modes of the structure activated by the wind loads. Under earthquake excitations the bottom region is also critical in most cases but in some of them the upper part of the tower triggers the collapse. The latter occurs because of the contribution of high-order vibration modes in the earthquakes dominated by short periods, characteristic of rocky ground conditions. In addition, it is found that long-period ground motions tend to magnify the response of the structure in the elastic range and have associated a higher probability of failure for the same peak ground acceleration. It is concluded that the response of the wind turbine under extreme dynamic actions is strongly dependent on the relationship between the frequency content of the excitation and the structural response.