%0 Journal Article
%T Damage Localization and Quantification of Truss Structure Based on Electromechanical Impedance Technique and Neural Network
%A Cunfu He
%A Shen Yang
%A Zenghua Liu
%A Bin Wu
%J Shock and Vibration
%D 2014
%R 10.1155/2014/727404
%X Truss structure is widely used in civil engineering. However, it is difficult to quantitatively monitor the state of truss structures because of the connection diversity and complexity of truss structures. In this paper, electromechanical impedance (EMI) technique was proposed to measure impedance spectra by using PZT elements and backpropagation (BP) neural network was used as an effective nonlinear conversion tool to quantify the health state of truss structures. Firstly, frequency band of the spectrum was experimentally determined by the trial-and-error approach. Then four connection rods of this truss structure were selected for experimental research. These connection rods were loosened gradually with a small angle increment and the impedance spectra were recorded. Then, the measured data were compressed through dividing the frequency range into multiple subbands. And RMSD values of these bands showed that data points were reduced while damage features remained. Finally, one four-layered BP neural network model was constructed based on these compressed data. The research results showed that compressed impedance data could retain their damage features. After the training, the developed neural network model could not only determine the location of loosened rod, but also quantify the loosening levels. 1. Introduction As an effective structural health monitoring technique, electromechanical impedance (EMI) technique has gained widespread attention for its traits of high local sensitivity, easy installation of sensors, and nonparametric model analysis [1¨C3]. EMI technique has unique advantages, especially in the field of real-time health monitoring of some complex and irregular structures, such as truss structures [4] and connection bolts [5]. The influence of the added mass and shape of PZT patches was also reported [6]. Sun et al. [4] first proposed EMI technique to monitor the health state of truss structures and validated the effectiveness and potential of this technique to characterize such complex and irregular structures. Yan et al. [7] combined EMI technique with reverberation matrix method to quantitatively evaluate structural damage in Timoshenko beams. To solve the difficulty in the evaluation of damage severity and location, Yang and Divsholi [8] and Divsholi and Yang [9] divided the whole testing frequency range into multiple subbands. Annamdas and Yang [10] adopted EMI technique to monitor the health state of excavation support structures after experimental study. The result showed that, although the variations in signatures were not
%U http://www.hindawi.com/journals/sv/2014/727404/