Abstract
The output-only modal analysis for bridge structures based on improved empirical mode decomposition (EMD) is investigated in this study. First, a bandwidth restricted EMD is proposed for decomposing nonstationary output measurements with close frequency components. The advantage of bandwidth restricted EMD to standard EMD is illustrated by a numerical simulation. Next, the modal parameters are extracted from intrinsic mode function obtained from the improved EMD by both random decrement technique and stochastic subspace identification. Finally, output-only modal analysis of a railway bridge is presented. The study demonstrates the mode mixing issues of standard EMD can be restrained by introducing bandwidth restricted signal. Further, with the improved EMD method, band-pass filter is no longer needed for separating the closely spaced frequency components. The modal parameters extracted based on the improved EMD method show good agreement with those extracted by conventional modal identification algorithms.
Highlights
Monitoring, maintenance, and management at operation stage play an important role in the whole life span of largescale bridge structures
Starting from the nonstationary vibration measurements and closely spaced mode of bridge structures, this paper has developed a bandwidth restricted empirical mode decomposition (EMD) for output-only modal analysis
The mode mixing problem of standard EMD when dealing with closely spaced modes has been effectively restrained by the improved EMD
Summary
Monitoring, maintenance, and management at operation stage play an important role in the whole life span of largescale bridge structures. Modal analysis is often performed based on both input and output measurements of structures, meaning special excitation devices, such as drop weights, shakers, are needed These requirements are difficult to be fulfilled for large-scale bridge structures. Yang’s study pointed out that limited by poor frequency resolution of wavelet transform (WT), the identified results from HHT seem to be more accurate than those from WT He et al [24] extracted the modal parameters of Nanjing Railway Bridge based on empirical mode decomposition (EMD) and random decrement technique (RDT). Without band-pass filter, the closely spaced modes can be well separated with bandwidth restricted EMD Both RDT and SSI algorithm are employed to identify modal parameters when the single frequency component of original signal is obtained.
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