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Vibration chains are of interest in many fields of practical applications. In this contribution, a modal analysis of the rather special Mikota's vibration chain is performed. Herein, focus is set on the mode shapes of this multibody oscillator, which was firstly introduced by Mikota as a solid body compensator in hydraulic systems for filtering out fluid flow pulsations. The mode shapes show interesting properties, e.g. an increase in the polynomial representing the coordinates of each mode shape with an increasing eigenfrequency associated with the respective mode shape. This and other properties are discussed exemplary. Some of these properties still have to be proven, which is the task of future work. Additionally, modal damping of Mikota's vibration chain is discussed. Moreover, an approach for determining the damping matrix for given Lehr's damping measures without knowing the mode shapes in advance is introduced. This approach involves the determination of a matrix root. [ABSTRACT FROM AUTHOR]

The widespread usage of prestressed concrete (PC) box girder with corrugated steel webs (CSWs) can be attributed to its many remarkable merits over traditional concrete box girders, such as significantly reducing the deadweight of the girder, speeding up the construction process, avoiding the problem of web cracking and increasing the prestress introduction efficiency. Numerous previous studies were conducted to investigated the mechanical properties of CSWs as well as simply supported box girder bridges with CSWs, whereas very few studies focused on the FE modeling methods of continuous PC box girders with CSWs. In addition, experimental work on scale bridge models or full-scale bridges adopting the box girder with CSWs is very limited. In this paper, an equivalent orthotropic web (EOW) model was developed for CSWs and used to analyze the performance of the continuous PC box girder bridges with CSWs. To verify this model, a one-tenth-scale bridge model was developed for an existing continuous PC box girder bridge with CSWs. Both static and dynamic tests were carried out on this scale bridge model. The results obtained from the bridge finite element (FE) model with EOWs were compared to the results obtained from the bridge FE model with CSWs and also the experimental results from the scale bridge model. Good agreement was achieved between these results, indicating that the EOW model can provide a trustworthy and convenient tool in the FE analysis of PC continuous box girder bridges with CSWs. [ABSTRACT FROM AUTHOR]

Cable-stayed bridge is one of the most popular bridges in the world and is always the focus in engineering field. In this work, the in-plane free vibration of a multi-cable-stayed beam, which exists in cable-stayed bridge, has been studied. The general expressions are conducted for the multi-cable-stayed beam based on basic principle of the transfer matrix method. A double-cable-stayed beam is taken as an example and solved according to governing differential equations considering axial and transverse vibrations of cables and beam. Then, numerical analyses are implemented based on carbon fiber-reinforced polymer cables. The dynamic characteristics including natural frequencies and mode shapes are investigated and compared with those obtained by finite element model. Meanwhile, parametric analyses are carried out in detail aiming to explore the effects of parameters on natural frequencies of a two-cable-stayed beam. Finally, some interesting phenomena are revealed and a few interesting conclusions are also drawn. [ABSTRACT FROM AUTHOR]

This contribution deals with Mikota’s oscillator, a linear vibration chain with arbitrary n degrees of freedom. Of special interest are both the left- and right-eigenvectors of the undamped system. Investigating the first two right-eigenvectors leads to a conjecture concerning the general structure of the remaining n-2 right-eigenvectors. This general structure is proven, and an analytical expression is found which provides an efficient possibility to calculate all left- and right-eigenvectors in a successive manner. Additionally, it is revealed that the mode shapes of this special vibration chain are (partly) orthogonal to each other with respect to the standard scalar product. [ABSTRACT FROM AUTHOR]

In this article, a new method is proposed to determine the mode shapes of linear dynamic systems with proportional viscous damping excited by an impact force. The time signals of responses and a priori knowledge of the natural frequencies are required in this method. The method is particularly suitable for the wavelet techniques which can precisely estimate the natural frequencies. A previously proposed method based on a modified Morlet wavelet function with an adjusting parameter is used to identify the natural frequencies and damping ratios of system, and the mode shapes are estimated using the proposed method in this work. It is shown that the extracted mode shapes are not scaled. Therefore, mass change method is used for scaling the mode shapes. Moreover, the effect of noise on the extracted modal parameters is investigated. The validity of method is demonstrated using numerical and experimental case studies. [ABSTRACT FROM AUTHOR]

The main objectives of this study are to present a vibration-based damage identification method and also a denoising mode shape approach applicable to two-dimensional structures using curvelet transform. For this purpose, the curvelet transform via wrapping method is employed. The reliability of the proposed technique is demonstrated through a verification study by comparing the results of numerical and those of the experimental data in plate structures. Two case studies, one-story and three-story shear walls assuming damages at arbitrary locations, are examined in which different noise levels are included. Good agreement between the simulated and assumed damage in both example is demonstrated. The results confirm the robustness and high performance of the proposed method in detecting the damage in plate structure and eliminating the noises. [ABSTRACT FROM AUTHOR]