Experimental and Numerical Studies of the People Effects on a Structure Modal Parameters

Topics on the Dynamics of Civil Structures, Volume 1 - Conference Proceedings of the Society for Experimental Mechanics Series ◽

10.1007/978-1-4614-2413-0_3 ◽

2012 ◽

pp. 17-25 ◽

Cited By ~ 3

Author(s):

Anna Cappellini ◽

Stefano Manzoni ◽

Marcello Vanali

Keyword(s):

Modal Parameters ◽

Numerical Studies ◽

The People

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Detection of Cracks in Beam Structures Using Modal Analysis

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.105-107.689 ◽

2011 ◽

Vol 105-107 ◽

pp. 689-694

Author(s):

Pallab Das

Keyword(s):

Natural Frequencies ◽

Concrete Beams ◽

Mode Shapes ◽

Modal Parameters ◽

Multiple Cracks ◽

Flexibility Matrix ◽

Numerical Studies ◽

Linear Fracture ◽

Eigen Value ◽

Local Flexibility

In the present study, the modal parameters of cracked plain cement concrete beams have been studied theoretically. A crack in a beam element introduces considerable local flexibility, which has been expressed by local flexibility matrix, the dimension of which depends upon the numbers of degree of freedom considered. An approach based on linear fracture mechanics theory has been used to find flexibility matrix for the cracked element. The FEM program has been developed for eigen-value problems to determine the modal parameters of the cracked beams. Changes in natural frequencies and mode shapes between the damaged and intact beam have been observed. Numerical studies are performed by considering simply supported beam with single and multiple cracks at different locations with different crack depths.

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Damage Detection in Initially Nonlinear Structures Based on Variational Mode Decomposition

International Journal of Structural Stability and Dynamics ◽

10.1142/s0219455420420092 ◽

2020 ◽

Vol 20 (10) ◽

pp. 2042009

Author(s):

Yu Xin ◽

Jun Li ◽

Hong Hao

Keyword(s):

Damage Detection ◽

Structural Damage ◽

Dynamic Responses ◽

Modal Parameters ◽

Nonlinear Structures ◽

Variational Mode Decomposition ◽

Structural Dynamic ◽

Numerical Studies ◽

Mode Decomposition ◽

Frequency Domain Methods

Nonlinear characteristics in the dynamic behaviors of civil structures degrade the performance of damage detection of the linear theory based traditional time- and frequency-domain methods. To overcome this challenge, this paper proposes a damage detection approach for nonlinear structures based on Variational Mode Decomposition (VMD). In this approach, the measured dynamic responses from nonlinear structures under earthquake excitations are adaptively decomposed into a finite number of monocomponents by using VMD. Each decomposed mono-component represents an amplitude modulated and frequency modulated (AMFM) signal with a limited frequency bandwidth. Hilbert transform is then employed to identify the instantaneous modal parameters of the decomposed monomodes, including instantaneous frequencies and mode shapes. Based on the identified modal parameters from the decomposed structural dynamic responses, two damage indices are defined to identify the location and severity of structural damage, respectively. To validate the effectiveness and accuracy of the proposed approach, a nonlinear seven-storey shear building model with four different damage cases under earthquake excitations is used in the numerical studies. In experimental verifications, data from shake table tests on a 12-storey scaled reinforced concrete frame structure with different earthquake excitations are analyzed with the proposed approach. The results in both numerical studies and experimental validations demonstrate that the proposed approach can be successfully applied for nonlinear structural damage identification.

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