Topic
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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TL;DR: Investigation and comparison of the effectiveness of a traditional modal strain energy method (Stubbs index) and a recently developed modal strains energy decomposition (MSED) method for damage localization indicate that the MSED method outperforms the Stubbs index method for structural damage detection.
Abstract: Modal strain energy based methods for damage detection have received much attention. However, most of published articles use numerical methods and some studies conduct modal tests with simple 1D or 2D structures to verify the damage detection algorithms. Only a few studies utilize modal testing data from 3D frame structures. Few studies conduct performance comparisons between two different modal strain energy based methods. The objective of this paper is to investigate and compare the effectiveness of a traditional modal strain energy method (Stubbs index) and a recently developed modal strain energy decomposition (MSED) method for damage localization, for such a purpose both simulated and measured data from an offshore platform model being used. Particularly, the mode shapes used in the damage localization are identified and synthesized from only two measurements of one damage scenario because of the limited number of sensors. The two methods were first briefly reviewed. Next, using a 3D offshore platform model, the damage detection algorithms were implemented with different levels of damage severities for both single damage and multiple damage cases. Finally, a physical model of an offshore steel platform was constructed for modal testing and for validating the applicability. Results indicate that the MSED method outperforms the Stubbs index method for structural damage detection.
17 citations
TL;DR: In this paper, the structural health monitoring (SHM) benchmark problem of the Canton tower is studied based on the field monitoring data from the 20 accelerometers deployed on the tower, some modal frequencies and mode shapes at measured degrees of freedom of the tower are identified.
Abstract: In this paper, the structural health monitoring (SHM) benchmark problem of the Canton tower is studied. Based on the field monitoring data from the 20 accelerometers deployed on the tower, some modal frequencies and mode shapes at measured degrees of freedom of the tower are identified. Then, these identified incomplete modal data are used to update the reduced finite element (FE) model of the tower by a novel algorithm. The proposed algorithm avoids the problem of subjective selection of updated parameters and directly updates model stiffness matrix without model reduction or modal expansion approach. Only the eigenvalues and eigenvectors of the normal finite element models corresponding to the measured modes are needed in the computation procedures. The updated model not only possesses the measured modal frequencies and mode shapes but also preserves the modal frequencies and modes shapes in their normal values for the unobserved modes. Updating results including the natural frequencies and mode shapes are compared with the experimental ones to evaluate the proposed algorithm. Also, dynamic responses estimated from the updated FE model using remote senor locations are compared with the measurement ones to validate the convergence of the updated model.
17 citations
TL;DR: In this article, the authors focus on quantification of damping non-proportionality present in a discrete vibratory system, where the information available is a set of identified system eigenvalues and eigenvectors and the system parameters such as mass, stiffness, and damping matrices are unknown a priori.
17 citations
TL;DR: In this paper, a complex modal truncation augmentation method is proposed for the non-classically damped systems, which considers the contributions from the high vibration modes and can therefore increase the prediction accuracy of the structural responses.
Abstract: A complex modal truncation augmentation method is proposed in the present study for the non-classically damped systems. Compared to the traditional mode displacement superposition approach, this method considers the contributions from the high vibration modes and can therefore increase the prediction accuracy of the structural responses. It can be regarded as an improvement of the traditional method. Based on this method, the conventional CCQC (Complex Complete Quadratic Combination) modal combination rule for the non-classically damped systems is extended to take into account the contributions of the truncated high vibration modes and the effects of narrow-band inputs on the modal cross-correlation coefficients. Moreover, a practical method is developed to estimate the velocity response spectrum that is required in the CCQC rule utilizing the commonly used displacement response spectrum based on the random vibration theory. Numerical results show that the extended CCQC rule can result in more accurate structural response estimations especially when the contributions from the high vibration modes to the structural responses cannot be neglected or when the structure is subjected to the seismic inputs with narrow band widths.
17 citations
TL;DR: In this paper, a nonparametric estimation of multivariable frequency response functions can be more easily based on an error-in-variables (EINV) stochastic framework, and the application of a well-chosen multisine excitation permits improvement of the data quality, as well as the detection, qualification and quantification of nonlinear distortions during FRF measurements.
17 citations