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Using an inertial part of a building structure as a tuned mass damper (TMD) has been shown to have economic advantages in terms of required materials and space for installing and operating a TMD in a building. This study suggests either designing the top story of a new asymmetric-plan building or adding a purposely designed story atop an existing asymmetric-plan building as a TMD to protect the building against earthquakes. This novel TMD, called a top-story mass damper (TSMD), is formulated using the three-degree-of-freedom modal properties of the first triplet of vibration modes of the original two-way asymmetric-plan building. The so-called first triplet of vibration modes are the first dominant modes in each of the three directions, i.e., the two horizontal translations and one vertical rotation. The proposed TSMD is intended to suppress the vibrations resulting from the first triplet of vibration modes that are generally most significant in overall seismic responses. The effectiveness of the TSMD is verified by investigating the frequency response functions and seismic responses of one single-story and one 20-story two-way asymmetric-plan buildings. [ABSTRACT FROM AUTHOR]

The planetary gear system is the important part of the cutting unit in a coal shearer, and its performance is directly related to the output efficiency in coal mines. Analyzing the natural frequencies and vibration modes of a planetary gear system in a coal shearer is helpful for designing and monitoring the planetary gear system. So a lateral-torsional coupled free vibration model is proposed with the shaft stiffness of the sun gear based on the analysis of a purely torsional model. The solutions are determined by using the modal superposition method. Taking the planetary gear system in the cutting unit of a YBCS2-400 type coal shearer as an example and studying the natural characteristics, the vibration modes of the undamped system could be classified into three types – rotational mode, translational mode and planet mode. The associated reduced-order eigenvalue for each type of vibration mode is derived and the analytical expression of natural frequency is presented for the planet mode. The established model is validated by comparing it with the results of a finite element model, and the effect on the vibration frequencies of the transmission and width ratio has been obtained by means of the finite element model. [ABSTRACT FROM PUBLISHER]

Vibration of a hollow circular plate subjected to a rotating peripheral force is analytically studied in this paper. Closed-form solutions are developed in a series form for the plate deflection as well as the distributions of the strain and stress. The Galerkin approach is adopted as the solution method and a finite element model has also been developed. Computer simulations were performed to verify the model and solution methods were adopted. Close agreement is observed when comparing the numerical results with those obtained from the analytical technique. The acoustic pressure field is eventually obtained in front of the vibrating plate surface using the Rayleigh integral method. The solution procedure presented and the numerical results obtained can be extensively utilized in the noise source separation. This has always been a significant challenge in many engineering applications such as the railway wheel-rail dynamics or that of the automotive gear trains. [ABSTRACT FROM PUBLISHER]