An embeddable spherical smart aggregate for monitoring concrete hydration in very early age based on electromechanical impedance method

In this paper, a new embeddable spherical smart aggregate (SSA) was utilized to monitor concrete curing in very early age. Overcoming the limitation of the existing PZT-patch-based transducers, the SSA provides vital changing information in all directions of host structure. To verify the advantage of SSA in structural health monitoring (SHM), the sensitivities of SSA and smart aggregate (SA) in monitoring concrete cube deformation and stiffness variation were analyzed and compared by numerical simulation. The feasibility of SSA in monitoring the concrete hydration process was studied by experiments utilizing electromechanical impedance (EMI) technique. At last, four SSAs were embedded in a concrete column to study the practicality of SSA in monitoring the concrete curing process in very early age. The EMI signatures and the root mean square deviation (RMSD) values of the collected information from SSAs were analyzed. The results illustrate that the SSA is more sensitive than SA in monitoring the concrete deformation and stiffness variation. The data measured by SSA in monitoring the concrete hydration process fluctuates more obviously than the data recorded by SA. The new spherical transducer can effectively and reliably monitor the concrete hydration process.

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Nonlinear Modeling of Cracked Beams for Impedance Based Structural Health Monitoring

Volume 4B: Dynamics, Vibration, and Control ◽

10.1115/imece2017-70808 ◽

2017 ◽

Cited By ~ 1

Author(s):

Naserodin Sepehry ◽

Firooz Bakhtiari-Nejad ◽

Mahnaz Shamshirsaz ◽

Weidong Zhu

Keyword(s):

Structural Health Monitoring ◽

Linear System ◽

Frequency Response ◽

Frequency Domain ◽

Health Monitoring ◽

Impedance Method ◽

Breathing Crack ◽

Electromechanical Impedance ◽

Structural Health ◽

System Equations

One of the main objectives of the structural health monitoring by piezoelectric wafer active sensor (PWAS) using electromechanical impedance method is continuously damage detection applications. In present work impedance method of beam structure is considered and the effect of early crack using breathing crack modeling is studied. In order to model the effect of a crack in beam, the beam is connected with a rotational spring in crack location. The Rayleigh–Ritz method is used to generate ordinary differential equation of cracked beam. Firstly, only open crack is considered that this is leads to linear system equation. In linear system, time domain system equations are converted to frequency domain, and then impedance of PWAS in frequency domain is calculated. Secondly, the breathing crack is modeled to be fully open or fully closed. This phenomenon leads to the nonlinear system equations. These nonlinear equations are solved using pseudo-arc length continuation scheme and collocation method for any harmonic voltage applied to actuator. Then impedance of PWAS is calculated. Two methods are used to detect early crack using breathing crack modeling on PWAS impedance. At the first, frequency response of breathing crack in the frequency range with its sub-harmonics is calculated. Second, only frequency response of one harmonic is computed with its super-harmonics. Finally, the detection method of linear is compared with nonlinear model.

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Truss Structure Health Monitoring Based on Electromechanical Impedance Method

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.330.357 ◽

2013 ◽

Vol 330 ◽

pp. 357-363

Author(s):

Cun Fu He ◽

Xiao Ming Cai ◽

Shen Yang ◽

Zeng Hua Liu ◽

Bin Wu

Keyword(s):

Neural Network ◽

Health Monitoring ◽

Truss Structure ◽

Truss Structures ◽

Impedance Method ◽

Nonparametric Model ◽

Impedance Spectra ◽

Frequency Range ◽

Electromechanical Impedance ◽

Piezoelectric Elements

Truss structure is widely used in civil engineering applications for its advantages of easy transportation, convenient assembly and uniform loading. However, it is difficult to achieve real-time health monitoring because of connection diversity and complexity of truss structures. As a novel structural health monitoring technique, electro-mechanical impedance method could monitor the health state of one structure by measuring the spectra of impedance or admittance of the piezoelectric elements, which are bonded on the surface of this structure. This approach has the advantages of nonparametric model analysis, easy sensor installation and high local sensitivity, especially in sensitive frequency range. The damage information, which is tested and recorded by using electromechanical impedance method, could convert into intuitive results through neural network because of its good ability for nonlinear mapping. In this paper, a three-layer assembly truss structure was chosen as experimental object, piezoelectric elements were bonded on structure joints to measure structural impedance spectra, the change of these structural impedance spectra was tested and recorded under high frequency excitations when different truss bars were loosed, and then, one back-propagation (BP) neural network was built and trained by this damage information, which were treated as input samples. These results show that the sensitivity of impedance method is not the same to different frequency range and trained neural network could quickly identify loosen truss bars.

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Electromechanical Impedance Method for Damage Detection of Typical Joint on Jacket Platform

Volume 5: Pipelines, Risers, and Subsea Systems ◽

10.1115/omae2018-77385 ◽

2018 ◽

Author(s):

Boying Zhang ◽

Hamad Hameed ◽

Yuxin Xu ◽

Chonglin Zhang ◽

Yong Bai

Keyword(s):

Health Monitoring ◽

Mechanical Impedance ◽

Theoretical Background ◽

Impedance Method ◽

Laboratory Measurements ◽

Direct Evaluation ◽

Jacket Platform ◽

Health Monitoring System ◽

Electromechanical Impedance ◽

Experimental Works

Health monitoring of welded structural joints is a very important factor of the engineering community. Electro-mechanical impedance (EMI) technique allows the direct evaluation of structural dynamics by evaluating its E/M impedance or admittance signatures. This paper first gives a brief introduction of the theoretical background on the described method. Then, the described EMI technique is applied to recognize the presence of damage by executing experimental works where the damage in the form of crack is simulated with an impedance analyzer at various distances. Four typical welded metallic joints on a jacket platform successfully produced submillimeter cracks under cyclic loading and root mean square deviation (RMSD) is used to evaluate the degree of crack damage. Finally, an outcome of laboratory measurements performed with developed structural health monitoring system based on the electromechanical impedance phenomenon is presented.

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Deep Learning Based Structural Health Monitoring Framework with Electromechanical Impedance Method

Transactions on Engineering Technologies ◽

10.1007/978-981-32-9808-8_2 ◽

2019 ◽

pp. 13-24

Author(s):

Alex W. H. Choy ◽

Daniel P. K. Lun

Keyword(s):

Deep Learning ◽

Structural Health Monitoring ◽

Health Monitoring ◽

Impedance Method ◽

Electromechanical Impedance ◽

Structural Health ◽

Monitoring Framework

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Embedded piezoelectric transducers based early-age hydration monitoring of cement concrete added with accelerator/retarder admixtures

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20969916 ◽

2020 ◽

pp. 1045389X2096991 ◽

Cited By ~ 1

Author(s):

Demi Ai ◽

Chengxing Lin ◽

Hongping Zhu

Keyword(s):

Heat Effect ◽

Hydration Heat ◽

Strength Development ◽

Early Age ◽

Strength Gain ◽

Element Analysis ◽

Electromechanical Impedance ◽

Hardening Process ◽

Concrete Hydration ◽

Early Age Hydration

Accelerator/retarder admixtures are often added into concrete to improve its early-age strength, which needs to be effectively monitored during its hardening process. The electromechanical impedance (EMI) technique has validated its effectiveness for concrete hydration monitoring, this study attempted to extend the EMI technique to monitor 28-day age of strength gain in concrete that added with accelerator/retarder admixtures. Two types of new piezoelectric (PZT) transducers namely cement/aluminum embedded PZT (CEP/AEP) were proposed for EMI monitoring. The feasibility of the CEP and AEP was first verified via finite element analysis, where hydration heat effect on the two types of transducers was comparatively evaluated by numerical modeling. In the experiment, CEP/AEP transducers were applied to monitor the strength gain in concrete cubes, where characteristics of EMI signature and its statistical indices including root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD) were analyzed and correlated to strength development in concrete. Monitoring results demonstrated that concrete hydration triggered by retarder/accelerator were successfully captured by EMI signature. RMSD and MAPD indices further indicated that AEP had preferable performance than CEP transducer for monitoring early-age strength gain of concrete, as it could immune from hydration heat effect.

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