Abstract
Large civil structures such as bridges must be permanently monitored to ensure integrity and avoid collapses due to damage resulting in devastating human fatalities and economic losses. In this article, a wavelet-based method called the Wavelet Energy Accumulation Method (WEAM) is developed in order to detect, locate and quantify damage in vehicular bridges. The WEAM consists of measuring the vibration signals on different points along the bridge while a vehicle crosses it, then those signals and the corresponding ones of the healthy bridge are subtracted and the Continuous Wavelet Transform (CWT) is applied on both, the healthy and the subtracted signals, to obtain the corresponding diagrams, which provide a clue about where the damage is located; then, the border effects must be eliminated. Finally, the Wavelet Energy (WE) is obtained by calculating the area under the curve along the selected range of scale for each point of the bridge deck. The energy of a healthy bridge is low and flat, whereas for a damaged bridge there is a WE accumulation at the damage location. The Rio Papaloapan Bridge (RPB) is considered for this research and the results obtained numerically and experimentally are very promissory to apply this method and avoid accidents.
Highlights
The structural evaluation to determine damage, deterioration and/or abnormal operating conditions in complex civil structures is essential to determine the operational reliability and residual life of them [1]
All the types of mother wavelets that can be selected with MATLAB and different types of filters were implemented; the best results to identify damage were obtained with types of filters were implemented; the best results to identify damage were obtained with the Mexican hat mother wavelet and a Savitzky-Golay filter
These data corresponded with the measurements on the deck obtained with strain gages (125 Hz of sampling frequency), see Figure 6a. As it was mentioned previously, a controlled test, with the adequate instrumentation to follow the steps of the Wavelet Energy Accumulation Method (WEAM), was not possible to be performed early enough to warn about the damage on cable T1S5, to avoid its fault
Summary
The structural evaluation to determine damage, deterioration and/or abnormal operating conditions in complex civil structures is essential to determine the operational reliability and residual life of them [1]. Most of the damage detection programs are based on visual inspections, which are expensive and limited in access to all parts of the structure. Recent health monitoring systems for structures include different non-destructive tests, but in all cases the evaluation is localized and do not allow global evaluations of the structures [2]. It has been recognized that vibration analysis and modal analysis are the only techniques that have the potential for global evaluation of structures [1,3]. In these cases, health monitoring is carried out by analyzing changes in the characteristic behavior of vibration through natural frequencies, damping ratios and modal shapes. For the particular case of the vehicular bridges it is still necessary to increase the efforts to provide more sophisticated and reliable methods for early damage identification, since there are many documented cases of catastrophic failures of these structures even in the most developed countries
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