Application of Spatial Displacement Measurement on Damage Assessment from both Local and Global Structural System
Date Issued
2012
Date
2012
Author(s)
Li, Chi-Hang
Abstract
In this research, the capability of advance spatial displacement measurement for structural health monitoring (SHM) is studied. The method for obtaining this kind of data is different from regular measuring system. It utilizes the optical processing technique to calculate the specific particles’ locations (called targets) within an image. While taking image and compute the locations over time, the dynamic motion can be estimated. This research employed the three dimensional displacement from optical sensors to identify system and perform damage assessment.
The applied signal analysis methodologies can separate into two categories, global system identification and local element motion detection. For global system, two subspace methods including 1.covariance-driven stochastic subspace identification (SSI-COV) and 2.recursive subspace identification (RSI) are examined. They can obtain the system natural frequency and damping ratio based on different condition. The other method is 3.principal component analysis (PCA), which the system normal modes can be briefly calculated while the measured locations are distributed along the system. For local motion, we can discretize the targets into a set of local elements. These elements motion is detect by 4.singular spectral analysis (SSA), 5.continuous wavelet transform (CWT), and 6.finite element method (FEM). The extracted information is used to describe the structural local properties and detect the damage occurrence. To examine the applications of these methodologies on real three dimensional displacement data, a shake table test of one-story two-bay RC frame performed in the NCREE is selected. This experiment installed a totally integrated optical measuring system (DMM, by NDI Inc.) on its central column to obtain the displacement. The analysis results show that this kind of data is capable for system identification, and the detection of damage is also feasible. Detail analyzes the discrete elements. The damage location may be obtained.
Subjects
Structural health monitoring
spatial displacement
signal processing
singular spectral analysis
finite element method
Type
thesis
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