Dual use of PZT patches as sensors in global dynamic and local electromechanical impedance techniques for structural health monitoring

2011 ◽  
Vol 22 (16) ◽  
pp. 1841-1856 ◽  
Author(s):  
Rama Shanker ◽  
Suresh Bhalla ◽  
Ashok Gupta ◽  
Matta Praveen Kumar

In this article, a new approach is proposed to effectively detect the initiation and progression of structural damage by combining the global dynamic and the local electromechanical impedance (EMI) techniques, using the same set of surface-bonded piezoelectric ceramic (PZT) patches as sensors. The PZT patches are used to determine the natural frequencies and the strain mode shapes of the structure (for use in the global dynamic technique) as well as to acquire the electromechanical admittance signature (for use in the EMI technique) to facilitate an improved damage assessment. Occurrence and location of the incipient damage are determined using the EMI technique, whereas for moderate to severe damages, the location and the severity are arrived at through the global dynamic technique. Finally, damage severity is determined in terms of the original stiffness of structure using the strain mode shapes directly determined using the PZT patches. The proposed technique is illustrated using two specimens—a 4-m long steel beam and a mild steel plate 1260 mm × 630 mm × 6.5 mm in size. The integrated approach provides greater information about damage, is simple to apply, does not involve any numerical/analytical modeling a priori, and is at the same time very cost effective.

2021 ◽  
pp. 136943322110384
Author(s):  
Xingyu Fan ◽  
Jun Li ◽  
Hong Hao

Vibration based structural health monitoring methods are usually dependent on the first several orders of modal information, such as natural frequencies, mode shapes and the related derived features. These information are usually in a low frequency range. These global vibration characteristics may not be sufficiently sensitive to minor structural damage. The alternative non-destructive testing method using piezoelectric transducers, called as electromechanical impedance (EMI) technique, has been developed for more than two decades. Numerous studies on the EMI based structural health monitoring have been carried out based on representing impedance signatures in frequency domain by statistical indicators, which can be used for damage detection. On the other hand, damage quantification and localization remain a great challenge for EMI based methods. Physics-based EMI methods have been developed for quantifying the structural damage, by using the impedance responses and an accurate numerical model. This article provides a comprehensive review of the exciting researches and sorts out these approaches into two categories: data-driven based and physics-based EMI techniques. The merits and limitations of these methods are discussed. In addition, practical issues and research gaps for EMI based structural health monitoring methods are summarized.


2017 ◽  
Vol 17 (6) ◽  
pp. 1441-1459 ◽  
Author(s):  
Dimitrios Anastasopoulos ◽  
Maure De Smedt ◽  
Lucie Vandewalle ◽  
Guido De Roeck ◽  
Edwin P.B. Reynders

Vibration-based structural health monitoring of civil structures relies on the repeated identification of dynamic structural characteristics of the structure from output-only vibration data. Natural frequencies and displacement mode shapes are the most commonly employed dynamic characteristics; yet their sensitivity to local damage of moderate severity is rather low with respect to their sensitivity to other factors such as temperature, necessitating data normalization. Strain mode shapes offer a higher sensitivity to local damage, but their accurate identification in a dense grid is challenging given the very small dynamic strain levels that are encountered under ambient excitation. In this article, a method is presented for tackling this challenge. It consists of three stages. First, fiber-optic Bragg grating strain sensors are attached to the structure and interrogated with a tunable laser performing a wavelength sweep. In this way, the measured strain amplitudes have the required accuracy but synchronization errors are introduced between the different Bragg sensors. Second, a modal analysis is performed on the dynamic strain data using an accurate parametric system identification technique. This is followed by a synchronization step which compensates for the delays introduced by the wavelength sweep. Finally, the synchronized strain mode shapes are employed as damage-sensitive features, either directly or via a newly proposed quantity, the top-to-bottom strain ratio. The method is validated by progressive damage testing of a complex, prestressed concrete “roof” beam, reinforced with steel fibers. It is observed that the proposed method can identify both the presence and the location of the damage in a relatively early stage.


Author(s):  
Rama Shanker ◽  
Suresh Bhalla ◽  
Ashok Gupta

This paper describes an experimental study to extract the dynamic characteristics of a two-storey reinforced concrete (RC) frame structure using piezo-electric ceramic (PZT) patches. PZT patches were embedded in the structure at the time of construction. Basically two techniques were applied to monitor the health of structure, the global dynamic technique and the local electro-mechanical impedance (EMI) technique. Global dynamic technique, which is based on frequency changes, is effective in low frequency range only. Due this limitation, initial damage/hair crack can not be detected by the global dynamic technique. On the other hand, EMI technique acts at higher frequency range and is very sensitive to detect the initial damage/hair cracks. The lower natural frequencies of the frame structure were determined experimentally using global techniques. The two-storey R.C. frame was modeled using ANSYS 9.0 to determine the frequencies numerically. Experimental results were compared with numerical results, which were found to be agreeable. Initial cracks were detected by the EMI technique. Severity and location of damage can be also determined with the help of these parameters. Inputs were chosen from these parameters to train an artificial neural network (ANN) whose outputs were the severity and the location of damage. Thus, complete monitoring can be done by the combination of global vibration and EMI technique using PZT patches. This integrated approach can be used for damage/crack detection at very early stage. This approach is very sensitive and cost effective to predict the incipient damages in civil structures.


Sensors ◽  
2020 ◽  
Vol 20 (23) ◽  
pp. 6862
Author(s):  
Kang Yun ◽  
Mingyao Liu ◽  
Jiangtao Lv ◽  
Jingliang Wang ◽  
Zhao Li ◽  
...  

For engineering structures, strain flexibility-based approaches have been widely used for structural health monitoring purposes with prominent advantages. However, the applicability and robustness of the method need to be further improved. In this paper, a novel damage index based on differences in uniform load strain field (ULSF) is developed for plate-like structures. When estimating ULSF, the strain flexibility matrix (SFM) based on mass-normalized strain mode shapes (SMSs) is needed. However, the mass-normalized strain mode shapes (SMSs) are complicated and difficult to obtain when the input, i.e., the excitation, is unknown. To address this issue, the proportional strain flexibility matrix (PSFM) and its simplified construction procedure are proposed and integrated into the frames of ULSF, which can be easily obtained when the input is unknown. The identification accuracy of the method under the damage with different locations and degrees is validated by the numerical examples and experimental examples. Both the numerical and experimental results demonstrate that the proposed method provides a reliable tool for output-only damage detection of plate-like structures without estimating the mass-normalized strain mode shapes (SMSs).


2007 ◽  
Vol 30 (4) ◽  
pp. 1206-1209 ◽  
Author(s):  
Jaehoon Ha ◽  
Youngjin Park ◽  
Younsik Park

Author(s):  
K. Van Balen

This contribution examines the challenges posed to the cultural heritage documentation community (the CIPA community and others) in implementing a preventive conservation approach of the built heritage in today’s society. <u>The “DNA” of Preventive Conservation.</u><br><br> Various authors so far support the argument that preventive conservation is an effective way to respond to the challenges society faces with the preservation of its Cultural Heritage (Van Balen, 2013).<br><br> A few decades of experiences with the application of preventive conservation in the field of immovable heritage in the form of Monumentenwacht in The Netherland and in Flanders have shown that a good monitoring of the state of preservation with a strong push for maintenance activities contributes to more preservation of authenticity, to more cost-effective preservation and to empowering society in dealing with heritage preservation. (Cebron, 2008)<br><br> An analysis of these and similar experiences demonstrates that these “Monumentenwacht” activities represent only a part of what could be named a preventive conservation system. Other fields in which prevention is advocated for its higher efficiency, show the importance of system thinking in the development of improved strategies.<br><br> Applying this approach to the field of the immovable heritage, referring to the initial results shown by the Monumentenwacht practices, it becomes clear that different dimension are at stake simultaneously: the preservation of authenticity or integrity, the management of resources and the connection with society. It shows that the analysis of challenges in heritage preservation and the development of strategies is à priori multifaceted and therefor has a certain level of complexity.<br><br> The sustainability of the preservation of cultural heritage buildings and sites can be measured according to its multiple economic, social, environmental and cultural support. The Cultural Heritage Counts for Europe report shows that the more diverse the support is for cultural heritage preservation actions, the more those actions will contribute to sustainable development and the more sustainable the preservation of that heritage will be. This reasoning has led to the “upstream approach” which argues that cultural heritage preservation can benefit from a variety of resources which do not necessarily have to be earmarked for it à priori (CHCfE, 2015).<br><br> It leads to arguing for an holistic and integrated approach for cultural heritage preservation that taps into different kinds of resources, which requires acknowledgement of the complex nature of understanding and managing heritage values into an overall societal development goal (Vandesande, 2017).<br><br> <u>Challenges in the Cultural Heritage documentation field.</u><br><br> Documentation needs in the field of cultural heritage preservation therefor are challenged by the complexity of the sources of information, by the need to integrate them in an holistic tool and by the way they are able to dialogue with society.<br><br> 1. The proper analysis of heritage requires increasing efforts by the diversity of sources and the complexity of their interaction.This (complexity acknowledging) analysis should be linked to monitoring tools which eventually contribute to monitor culturalheritage values. This monitoring is also a documentation challenge as it has to be pertinent and dynamic. Analysis andmonitoring are important as they are the basis for understand threats that impact heritage values.<br><br> 2. As resources for heritage development or heritage guided development can have a variety of origins, their documentation andanalysis –compared to the traditional curative object oriented preservation- should be extended to include many more possibleresources. Experiences exist with documentation of the physical environment of heritage sites but the upstream approachpoints toward a larger number of development resources that can be tapped into. This implies the need to identify newapproaches, to document them and to integrate them in a dynamic analytical process.<br><br> 3. As preventive conservation focusses not only on the empowerment of the owners and managers but also on a betterintegration of a wider group of stakeholders, the question of ownership and continuous co-creation challenges thedocumentation process as well.<br><br> 4. Longevity of documentation: the need for continuous updating and monitoring as part of the cyclic approach of PC challengesthe longevity, accessibility of the documentation itself and the tools that will use them in the future.


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