EXPERIMENTAL TESTS ON LOCAL DAMAGE DETECTION USING OPTICAL FBG SENSORS

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Jin-Hak Yi
Keyword(s):  
Damage Detection ◽  
Environmental Effects ◽  
Detection Method ◽  
Principal Component ◽  
Experimental Tests ◽  
Scale Model ◽  
External Loading ◽  
Local Damage ◽  
Offshore Structure ◽  
Load Variations

In this study, the fiber Bragg grating (FBG)-sensor based local damage detection method is proposed under circumstances with temperature and external loading variations. To compensate the environmental effects, principal component analysis (PCA) is utilized and also the performance of PCA is compared with that of the conventional linear adaptive filter (LF) model. Laboratory tests with a 1/20 scale model of a jacket-type offshore structure with six jacket-legs and a heavy super structure have been carried out for investigating the performance of the proposed damage detection method. From the experimental tests, it is observed that the local damage feature is mostly hidden and difficult to identify due to the environmental effects. By utilizing the conventional LF and PCA models, the effects of the undesirable environmental effects can be efficiently eliminated, and it is also found that the performances of the LF and PCA models are very similar and competitive to each other. However PCA model does not require the information on the temperature and external load variations, hence it can be concluded that the PCA-based local damage detection can be more efficiently applied for FBG-based local damage detection under temperature and external loading variations.

scholarly journals Separating damage from environmental effects affecting civil structures for near real-time damage detection

2017 ◽  
Vol 17 (4) ◽  
pp. 850-868 ◽  
Author(s):  
William Soo Lon Wah ◽  
Yung-Tsang Chen ◽  
Gethin Wyn Roberts ◽  
Ahmed Elamin
Keyword(s):  
Damage Detection ◽  
Real Time ◽  
Environmental Effects ◽  
Environmental Conditions ◽  
Principal Component ◽  
Detection Methods ◽  
Real Time Monitoring ◽  
Civil Structures ◽  
Data Set ◽  
Wide Range

Analyzing changes in vibration properties (e.g. natural frequencies) of structures as a result of damage has been heavily used by researchers for damage detection of civil structures. These changes, however, are not only caused by damage of the structural components, but they are also affected by the varying environmental conditions the structures are faced with, such as the temperature change, which limits the use of most damage detection methods presented in the literature that did not account for these effects. In this article, a damage detection method capable of distinguishing between the effects of damage and of the changing environmental conditions affecting damage sensitivity features is proposed. This method eliminates the need to form the baseline of the undamaged structure using damage sensitivity features obtained from a wide range of environmental conditions, as conventionally has been done, and utilizes features from two extreme and opposite environmental conditions as baselines. To allow near real-time monitoring, subsequent measurements are added one at a time to the baseline to create new data sets. Principal component analysis is then introduced for processing each data set so that patterns can be extracted and damage can be distinguished from environmental effects. The proposed method is tested using a two-dimensional truss structure and validated using measurements from the Z24 Bridge which was monitored for nearly a year, with damage scenarios applied to it near the end of the monitoring period. The results demonstrate the robustness of the proposed method for damage detection under changing environmental conditions. The method also works despite the nonlinear effects produced by environmental conditions on damage sensitivity features. Moreover, since each measurement is allowed to be analyzed one at a time, near real-time monitoring is possible. Damage progression can also be given from the method which makes it advantageous for damage evolution monitoring.

ADAPTIVE-SCALE DAMAGE DETECTION FOR FRAME STRUCTURES USING BEAM-TYPE WAVELET FINITE ELEMENT: EXPERIMENTAL VALIDATION

2013 ◽  
Vol 07 (03) ◽  
pp. 1350024 ◽  
Author(s):  
SONGYE ZHU ◽  
WEN-YU HE ◽  
WEI-XIN REN
Keyword(s):  
Finite Element ◽  
Damage Detection ◽  
Experimental Validation ◽  
Detection Method ◽  
Human Vision ◽  
Scale Model ◽  
Multi Scale ◽  
Wavelet Finite Element ◽  
Portal Frame ◽  
Beam Type

The superior human vision system provides ingenious insight into an ideal damage detection strategy in which structural modeling scales are not only spatially varying but also dynamically changed according to actual needs. This paper experimentally examines the efficacy of a multi-scale damage detection method based on wavelet finite element model (WFEM). The beam-type wavelet finite element in this study utilizes the second-generation cubic Hermite multi-wavelets as interpolation functions. The dynamic testing results of a one-bay steel portal frame with multiple damages are employed in the experimental validation. Through a multi-stage updating of the WFEM, the multiple damages in the steel portal frame are detected in a progressive manner: the suspected region is first identified using a low-scale structural model, and the more accurate location and severity of the damage can be identified using a multi-scale model with local refinement. As the multi-scale WFEM considerably facilitates the adaptive change of modeling scales, the proposed multi-scale damage detection method can efficiently locate and quantify damage with minimal computation effort and a limited number of updating parameters and sensors, compared with conventional finite element methods.

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