Particle damping, an effective passive vibration control technology, is developing dramatically at the present stage, especially in the aerospace and machinery fields. The aim of this paper is to provide an overview of particle damping technology, beginning with its basic concept, developmental history, and research status all over the world. Furthermore, various interpretations of the underlying damping mechanism are introduced and discussed in detail. The theoretical analysis and numerical simulation, together with their pros and cons are systematically expounded, in which a discrete element method of simulating a multi-degree-of-freedom structure with a particle damper system is illustrated. Moreover, on the basis of previous studies, a simplified method to analyze the complicated nonlinear particle damping is proposed, in which all particles are modeled as a single mass, thereby simplifying its use by practicing engineers. In order to broaden the applicability of particle dampers, it is necessary to implement the coupled algorithm of finite element method and discrete element method. In addition, the characteristics of experimental studies on particle damping are also summarized. Finally, the application of particle damping technology in the aerospace field, machinery field, lifeline engineering, and civil engineering is reviewed at length. As a new trend in structural vibration control, the application of particle damping in civil engineering is just at the beginning. The advantages and potential applications are demonstrated, whereas the difficulties and deficiencies in the present studies are also discussed. The paper concludes by suggesting future developments involving semi-active approaches that can enhance the effectiveness of particle dampers when used in conjunction with structures subjected to nonstationary excitation, such as earthquakes and similar nonstationary random excitations. KEYWORDS discrete element method, impact damping, nonlinear energy sink, particle damping, passive control, semiactive control | INTRODUCTIONParticle damping technology is a form of an auxiliary-mass type vibration damper, wherein multiple metal, tungsten carbide, ceramic or other types of small particles are placed within the cavities of the vibrating structure, or the enclosures attached to the vibrating structure in order to mitigate the response of the primary structure. [1,2] As the primary structure vibrates, kinetic energy is significantly absorbed through the combined effects of particle-to-particle and particle-to-wall inelastic collisions and frictional losses, producing considerable damping to the primary structure. [3][4][5][6] Particle damping technology has been widely Received: 23 February 2017 Revised: used due to its conceptual simplicity, moderate cost, good durability, and temperature insensitivity. Provided that the operating temperature is below the particles' metal melting point, it could maintain normal operation. Furthermore, material such as tungsten powder can withstand the high temp...

SUMMARYTwo kinds of methods have been primarily used to improve the vibration performance of high-rise buildings. One approach is to enhance the structural lateral stiffness, which may increase the component size and inefficiently use material. The other approach is to employ vibration control devices, such as tuned mass dampers (TMDs), tuned liquid dampers (TLD) and other supplemental damping devices. This latter approach has proved to be quite economical and efficient, and as such, increasingly used in practice. The Shanghai Center Tower (SHC) is a super high-rise landmark building in China, with a height of 632 m. In order to mitigate its vibration during wind storms, a new eddy-current TMD was installed at the 125th floor. Special protective mechanisms were incorporated to prevent excessively large amplitude motion of the TMD under extreme wind or earthquake scenarios. Results of reduced-scale laboratory tests and field tests are presented in this paper to characterize the dynamic properties of the damping device and validate the fidelity of the numerical results. Results of structural analyses indicate that for SHC the eddy-current TMD was able to reduce wind-induced structural acceleration by 45%-60% and earthquake-induced structural displacement by 5%-15%. The installation of the TMD was completed in December 2014, and the performance observed to date is judged to be good.

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Nonlinear energy sinks (NES) are efficient vibration control devices, which have been studied and applied in mechanical, automobile, and aerospace engineering.However, there are few applications in civil engineering. A new type of NES, which is termed as track NES, is proposed in this paper. The optimal mass ratio and track shape expression of NES were determined based on a preliminary optimization design process. To verify its vibration control effects on building structures, a series of shake table tests were conducted on a five-story steel frame. Tracks of the NES were installed at the roof of the frame with rigid connections and the mass of the NES was constrained to slide along the track by using wheels. Five earthquake waves with different frequency spectrums were selected to excite the frame coupled with NES under minor, moderate, and major levels. Accelerations and displacements on each story of the frame were measured, recorded, and evaluated. The experimental results demonstrate that with small mass ratio (2%) of main structure, NES has good performance in reducing the dynamic responses of the frame under seismic excitations. The reduction ratio for peak response is up to 50%, while for root mean square response is up to 80%. NES also exhibits wide-band frequency vibration controlling attributes, and the responses of the frame are reduced in multiple vibration modes. In addition, the vibration reduction capability of the NES with steel wheels and that with rubber wheels are compared, and it is verified that different damping of NES makes a difference to the vibration control effects. The displacement reduction performance is not sensitive to the damping factor of the NES, but acceleration response is highly affected by the damping feature of the NES.