Abstract
The aim of this study is to modal parameter identification of a three-storey structure using operational modal analysis. In this research, available techniques in both time domain and frequency domain have been utilized. In time domain, the Stochastic Subspace Identification (SSI) technique, and in the frequency domain, Frequency Domain Decomposition (FDD) and Extended Frequency Domain Decomposition (EFDD) have been used. The modal parameters of a three-storey structure have been calculated using both experimental and finite element method. For this purpose, first, the three-storey structure was modeled in the ANSYS software and then, using the vibration analysis, structural responses are determined. The structure responses are used as inputs of the operational modal analysis algorithms and the modal parameters are obtained. Then, by constructing and exciting the structure by a variety of external excitation, the responses are measured and then, they are used as inputs to the operational modal analysis algorithm to obtain the modal parameters. Since the input signal in OMA method should be random, random, periodic random, pseudo-random, and burst random signals are used for exciting the structure. Finally, the calculated modal parameters from the finite element method and empirical method are compared with each other.
Highlights
Dynamic analysis is one the most important and widely used engineering tools in designing, construction and maintenance of the structures, but usually there is no analytical solution for complex structures
The three-storey structure modeled in the ANSYS software and using the vibration analysis, structural responses determined
The structure responses are used as inputs of the Operational Modal Analysis (OMA) algorithms and the modal parameters obtained
Summary
Dynamic analysis is one the most important and widely used engineering tools in designing, construction and maintenance of the structures, but usually there is no analytical solution for complex structures. They demonstrated that with the help of these two methods estimation of the modal parameters of the structure with good accuracy is feasible They obtained the power spectral density matrix of the responses, and determined the natural frequencies, damping coefficient and mode shapes by using the Singular Value Decomposition (SVD). Tarinejad et al [15] calculated the modal parameters of three-degree-of-freedom system by combining the FDD and wavelet transform methods They first modeled the system with random excitation in the MATLAB/Simulink software and obtained the time response. After 4 years, an earthquake occurred in the distance of 30 kilometers from California, this earthquake was lasted a few seconds, but was lead to a displacement in the structure for about three minutes They calculated the natural frequencies, damping coefficient and mode shapes of the structure by operational modal analysis and FDD method using ARTeMIS software. The calculated modal parameters from the finite element method and empirical method are compared with each other
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