Session: 01-08-01: Vibration and Acoustic Measurements, Signal Processing, and Test Facilities

Paper Number: 68740

Start Time: Wednesday, 01:50 PM

68740 - Output-Only Structural System Identification Based on Symplectic Geometry Mode Decomposition 

Structural system identification plays an important role in structural health monitoring because that the structural system parameters such as modal frequency, modal damping, and mode shapes are important parameters for the description of the dynamic characteristic of engineering structures. Identified accurate modal parameters are beneficial to finite element model updating, structural damage detection, and structural condition assessment, etc. The modal parameters of practical engineering structure can be obtained by widely used experimental modal analysis (EMA) and operational modal analysis (OMA). The EMA extracted modal parameters using the relationship between input and response data. In other words, it is essential to measure input and structural response simultaneously for EMA. As forced vibration testing of large-scale engineering structures is difficult and often costly, the OMA using only measured response under environmental and natural excitations is more feasible for engineering applications. A series of techniques have been developed and employed using output-only data in the field of structural system identification, mainly including the frequency-domain method and time-domain method. The frequency-domain method identified structural modal parameters by transforming the measured time-domain response signal into the frequency domain. As the response signal of the structure under operational states is easily polluted by noise, those methods often performed not always well. Another technique of structural system identification is the time-domain method such as stochastic subspace identification (SSI) methods, empirical mode decomposition (EMD), and variational mode decomposition (VMD). The SSI methods are the well-known method in time-domain identification techniques and are widely used in engineering applications. The EMD and VMD can decompose the response signal into a series of intrinsic mode functions (IMFs) which can be regarded as the estimation of modal response. However, the mode mixing and over binning are easily occurred in using EMD or VMD to decompose a structural response signal.

To overcome the above limitations, in this paper, a new structural system identification method with the output-only response is proposed to identify the modal properties of engineering structures based on symplectic geometry mode decomposition. Firstly, the newly developed symplectic geometry mode decomposition (SGMD) technique is utilized to decompose the vibration response into a limited number of IMFs. Then, the free decay responses (FDRs) of decomposed functions can be extracted from IMFs using the random decrement technique (RDT). Finally, the mode frequencies and damping ratio are identified from each FDR by using the Hilbert transform (HT) method. An advantage of the proposed method is that all the modal frequencies and damping ratios can be obtained by using the output response of only one suitable measuring point. In contrast with the VMD-based identification method, the proposed SGMD-based method can decompose response signal adaptively and does not require determining the parameters of VMD such as the number of the achieved IMFs and balancing parameter. Finally, some cases are conducted to demonstrate the validity and efficiency of the proposed method.

Presenting Author: Zhan Pengming Tongji University

Authors:

Zhan Pengming Tongji University
Qin Xianrong Tongji University
Zhang Qing Tongji University
Sun Yuantao Tongji University