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. 2024 Nov 28;24(23):7600.
doi: 10.3390/s24237600.

Operational Modal Analysis of Civil Engineering Structures with Closely Spaced Modes Based on Improved Hilbert-Huang Transform

Xu-Qiang Shang  1 , Tian-Li Huang  1 , Yi-Bin He  2 , Hua-Peng Chen  3
Affiliations

Operational Modal Analysis of Civil Engineering Structures with Closely Spaced Modes Based on Improved Hilbert-Huang Transform

Xu-Qiang Shang et al. Sensors (Basel). .

Abstract

In long-span bridges and high-rise buildings, closely spaced modes are commonly observed, which greatly increases the challenge of identifying modal parameters. Hilbert-Huang transform (HHT), a widely used method for modal parameter identification, first applies empirical mode decomposition (EMD) to decompose the acquired response and then uses the Hilbert transform (HT) to identify the modal parameters. However, the problem is that the deficiency of mode separation of EMD in HHT limits its application for structures with closely spaced modes. In this study, an improved HHT based on analytical mode decomposition (AMD) is proposed and is used to identify the modal parameters of structures with closely spaced modes. In the improved HHT, AMD is first employed to replace EMD for decomposing the measured response into several mono-component modes. Then, the random decrement technique is applied to the decomposed mono-component modes to obtain the free decay responses. Furthermore, the resulting free decay responses are analyzed by HT to estimate the modal parameters of structures with closely spaced modes. Examples of a simple three-degree-of-freedom system with closely spaced modes, a high-rise building under ambient excitation, and the Ting Kau bridge under typhoon excitations are adopted to validate the accuracy, effectiveness, and applicability of the proposed method. The results demonstrate that the proposed method can efficiently and accurately identify the natural frequencies and damping ratios of structures with closely spaced modes. Moreover, its identification results are more precise compared to those obtained using existing methods.

Keywords: analytical mode decomposition (AMD); civil engineering structures; closely spaced modes; improved Hilbert–Huang transform; operational modal analysis.

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Conflict of interest statement

Author Yi-Bin He was employed by the company Hunan Architectural Design Institute Group Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Flowchart of IHHT-based modal identification of structures with closely spaced modes.
Figure 2
Figure 2
The simulated 3-DOF spring-mass system.
Figure 3
Figure 3
(a) The recorded acceleration response and (b) its corresponding spectrum.
Figure 4
Figure 4
(a) The decomposed modes by EMD and (b) their Fourier spectrum.
Figure 5
Figure 5
(a) The decomposed modes by AMD and (b) their Fourier spectrum.
Figure 6
Figure 6
Logarithmic amplitude and phase curves in 3-DOF system: (a) mode 1, (b) mode 2, and (c) mode 3.
Figure 7
Figure 7
The simulated high-rise building with four additional lightweight appendages.
Figure 8
Figure 8
(a) The acceleration time history at the top of the lightweight appendage and (b) its corresponding Fourier spectrum.
Figure 9
Figure 9
(a) The decomposed mono-component modes by AMD and (b) their Fourier spectrum.
Figure 10
Figure 10
Logarithmic amplitude and phase curves in high-rise building: (a) mode 1, (b) mode 2, (c) mode 3, and (d) mode 4.
Figure 11
Figure 11
(a) Ting Kau Bridge and (b) layout of accelerometers installed on bridge deck.
Figure 12
Figure 12
(a) The measured acceleration time histories by accelerometer 17 and (b) its corresponding Fourier spectrum.
Figure 13
Figure 13
The obtained free decay response by RDT: (a) mode 1, (b) mode 2, and (c) mode 3.
Figure 14
Figure 14
The logarithmic amplitude and phase curves using the data from sensor 10: (a) mode 1, (b) mode 2, and (c) mode 3.
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