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Modal testing

About: Modal testing is a research topic. Over the lifetime, 4047 publications have been published within this topic receiving 64772 citations.


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Journal ArticleDOI
TL;DR: In this paper, the effects of higher modes on the geometric regularity of single-column-bent viaducts have been investigated by comparing modal parameters resulting from the elastic eigenvalue modal analysis with transverse displacements obtained from static modal pushover analyses.
Abstract: A structure is considered to be irregular in this paper if its response is influenced considerably by higher modes. Herein, the effects of the higher modes on the geometric regularity of single-column-bent viaducts have been investigated by comparing modal parameters resulting from the elastic eigenvalue modal analysis with transverse displacements obtained from static modal pushover analyses. A class of bridges with equal span lengths, but with different pier heights, has been considered in this study. For a better identification of the modal behavior of this class of bridges, several regularity indices are discussed. Some of these indices were used previously in model updating, model validation, and the determination of modal correlations in the field of experimental vibration analysis (modal testing) of mechanical and structural systems. Certain modifications have been applied to previous works in order to improve bridge regularity indices. New indices have also been proposed for the attainment of a more realistic representation of the structural particulars of such bridges to be consistent with the analytical methods addressed in the AASHTO Specifications, for practical design purposes. The results calculated with the aid of various indices are reported and compared.

16 citations

Journal ArticleDOI
Liang Gao1, Bolun An1, Tao Xin1, Ji Wang1, Wang Pu 
TL;DR: A model that is highly consistent with the vibration characteristics of the actual track structure is obtained, which can provide a reliable reference for modal testing, vibration analysis and model updating of ballastless track structures.

16 citations

Journal ArticleDOI
TL;DR: In this article, a frequency-domain technique that extends the concept of linear modal super position to nonlinear systems by using the normal nonlinear mode approach so that a generalized parameter identification method can be formulated for MDOF nonlinear system is presented.
Abstract: This work presents a frequency-domain technique that extends the concept of linear modal super position to nonlinear systems by using the normal nonlinear mode approach so that a generalized parameter identification method can be formulated for MDOF nonlinear systems. The methodology is compatible with existing established vibration analysis techniques such as finite element (FE) modeling and experimental modal analysis. Furthermore, once the nonlinear modal parameters are identified at some reference force level, the nonlinear response can be predicted at any arbitrary excitation level using standard modal sum mation techniques. The numerical study is focused on a 4-DOF system with friction damping nonlinearity, for which both the macro- and microslip representations are considered. Simulated nonlinear frequency re sponse functions, obtained for a given excitation level using a harmonic balance method, were subjected to a nonlinear modal analysis procedure, and the modal parameters were extracted as a fu...

16 citations

Journal ArticleDOI
TL;DR: The complete square root-of-sum of squares (c-SRSS) modal combination rule as mentioned in this paper is an improvement over the classical SRSS rule which neglects contributions from modal cross-covariances.
Abstract: The complete Square-Root-of-Sum-of-Squares (c-SRSS) modal combination rule is presented. It expresses the structural response in terms of uncoupled SDOF modal responses, yet accounting fully for modal response variances and cross-covariances. Thus, it is an improvement over the classical SRSS rule which neglects contributions from modal cross-covariances. In the c-SRSS rule the spectral moments of the structural response are expressed rigorously in terms of the spectral moments of uncoupled modal responses and of some coefficients that can be computed straightforwardly as a function of modal frequencies and damping, without involving the computation of cross-correlation coefficients between modal responses. An example shows an application of the c-SRSS rule for structural systems with well separated and closely spaced modal frequencies, subjected to wide-band and narrow-band excitations. Comparisons with response calculations using the SRSS and the Complete Quadratic Combination rules are given and discussed in detail. Based on the c-SRSS rule a response spectrum formulation is introduced to estimate the maximum structural response. An example considering a narrow-band excitation from the great Mexico earthquake of September 19, 1985, is given and the accuracy of the response spectrum formulation is examined. Copyright © 2010 John Wiley & Sons, Ltd.

16 citations

Proceedings ArticleDOI
01 Jan 2002
TL;DR: In this paper, the authors demonstrate the feasibility of using a multiple-input multiple-output (MIMO) modal testing technique on an inflated torus, using Macro-Fiber Composite (MFC® ) patches as both actuators and sensors.
Abstract: Inflated space-based structures have become popular over the past three decades due to their minimal launch-mass and launch-volume. Once inflated, these space structures are subject to vibrations induced by guidance systems and space debris as well as from variable amounts of direct sunlight. Understanding the dynamic behavior of space-based structures is critical to ensuring their desired performance. Inflated materials, however, pose special problems when testing and trying to control their vibrations because of their lightweight, flexibility, and high damping. Traditional modal testing techniques, based on single-input, single-output (SISO) methods, are limited for a variety of reasons when compared to their multiple counterparts. More specifically, SISO modal testing techniques are unable to reliably distinguish between pairs of modes that are inherent to axi-symmetric structures (such as an inflated torus, a critical component of a gossamer spacecraft). Furthermore, it is questionable as to whether a single actuator could reliably excite the global modes of a true gossamer craft, such as a 25 m diameter torus. In this study, we demonstrate the feasibility of using a multiple-input multiple-output (MIMO) modal testing technique on an inflated torus. In particular, the refined modal testing methodology focuses on using Macro-Fiber Composite (MFC® ) patches (from NASA Langley Research Center) as both actuators and sensors. MFC® patches can be integrated in an unobtrusive way into the skin of the torus, and can be used to find a gossamer structure’s modal parameters. Furthermore, MFC® excitation produces less interference with suspension modes of the free-free torus than excitations from a conventional shaker. The use of multiple actuators is shown to properly excite the global modes of the structure and distinguish between pairs of modes at nearly identical resonant frequencies. Formulation of the MIMO test as well as the required postprocessing techniques are explained and successfully applied to an inflated Kapton® torus.Copyright © 2002 by ASME

16 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202367
2022164
202141
202059
201967
201878