Mr. Bahador Sabet Divsholi Profile

Bahador Sabet Divsholi

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Proceedings Article | 18 April 2011 Paper

Comparison of embedded, surface bonded and reusable piezoelectric transducers for monitoring of concrete structures

Bahador Sabet Divsholi, Yaowen Yang

Proceedings Volume 7981, 798151 (2011) https://doi.org/10.1117/12.881471

KEYWORDS: Ferroelectric materials, Transducers, Electromagnetic coupling, Wave propagation, Sensors, Actuators, Damage detection, Structural health monitoring, Epoxies, Coating

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Piezoelectric lead zirconate titanate (PZT) transducers have been used for health monitoring of various structures over the last two decades. There are three methods to install the PZT transducers to structures, namely, surface bonded, reusable setup and embedded PZTs. The embedded PZTs and reusable PZT setups can be used for concrete structures during construction. On the other hand, the surface bonded PZTs can be installed on the existing structures. In this study, the applicability and limitations of each installation method are experimentally studied. A real size concrete structure is cast, where the surface bonded, reusable setup and embedded PZTs are installed. Monitoring of concrete hydration and structural damage is conducted by the electromechanical impedance (EMI), wave propagation and wave transmission techniques. It is observed that embedded PZTs are suitable for monitoring the hydration of concrete by using both the EMI and the wave transmission techniques. For damage detection in concrete structures, the embedded PZTs can be employed using the wave transmission technique, but they are not suitable for the EMI technique. It is also found that the surface bonded PZTs are sensitive to damage when using both the EMI and wave propagation techniques. The reusable PZT setups are able to monitor the hydration of concrete. However they are less sensitive in damage detection in comparison to the surface bonded PZTs.

Proceedings Article | 30 March 2009 Paper

Application of reusable PZT sensors for monitoring initial hydration of concrete

Bahador Sabet Divsholi, Yaowen Yang

Proceedings Volume 7292, 729222 (2009) https://doi.org/10.1117/12.815877

KEYWORDS: Ferroelectric materials, Sensors, Wave plates, Metals, Cements, Transducers, Aluminum, Solids, Electromagnetic coupling, Statistical analysis

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To increase the efficiency of in-situ casting or precast of concrete, determining the optimal time of demolding is very important for concrete suppliers. In the first few hours after mixing, the fresh concrete gradually achieves solid properties with reasonable compressive strength. Due to different type and amount of cementitious materials, concrete additives (e.g. retarders) and curing temperature, different rates of hardening are expected. In addition, some other factors like the quality of the cementitious materials further increase the uncertainty in determining appropriate time for demolding of concrete. Electro-mechanical impedance (EMI) based lead zirconate titanate (PZT) sensors have been used for damage detection and structural identification for various engineering structures. In this work, a reusable PZT sensor for monitoring initial hydration of concrete is developed, where a piece of PZT is bonded to a piece of metal with two bolts tightened inside of the holes drilled in the metal. An impedance analyzer is used to acquire the signature of this reusable sensor. During the concrete casting, the bolts and the bottom surface of the metal is set to penetrate part of the fresh concrete. At different stages of the first 48 hours after casting, the PZT signatures are acquired. A statistical analysis technique is employed to associate the change in concrete strength with the changes in the PZT admittance signatures. The results show that the developed sensor is able to effectively monitor the initial hydration of concrete, and can be detached from the concrete for future use.

Proceedings Article | 30 December 2008 Paper

Application of PZT sensors for detection of damage severity and location in concrete

Bahador Sabet Divsholi, Yaowen Yang

Proceedings Volume 7268, 726813 (2008) https://doi.org/10.1117/12.810696

KEYWORDS: Ferroelectric materials, Sensors, Electromagnetic coupling, Structural health monitoring, Damage detection, Ceramics, Statistical analysis, Nondestructive evaluation, Smart materials, Signal attenuation

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Piezoelectric ceramic lead zirconate titanate (PZT) based electromechanical impedance (EMI) technique has been applied for structural health monitoring (SHM) of various engineering systems. However, study on identification of damage severity and location is still in need. In the EMI method, the PZT electromechanical (EM) admittance is used as a damage indicator. Statistical techniques such as root mean square deviation (RMSD) have been employed to associate the damage level with the changes in the EM admittance signature. To achieve high sensitivity to damage, high frequency signatures (>200 kHz) have been used to monitor the region close to the PZT location. It has been reported that the use of RMSD as the damage indicator is difficult to specify the damage location and severity due to the inconsistency in the RMSD results. This paper proposes the use of large frequency (30-400 kHz) range and the RMSD values of sub-frequency intervals to eliminate the inconsistency in the results. An experiment is carried out on a real size concrete structure subjected to artificial damages. The PZT admittance signatures in a frequency range of 30 to 400 kHz for various structural damages have been recorded and the RMSD values of sub-frequency intervals of 10 kHz are calculated. Results show less inconsistency and uncertainties compared to the traditional method using limited high frequency range. It is observed that the damage close to the PZT changes the RMSD at high frequency range significantly; however the damage far away from the PZT changes the RMSD at low frequency range significantly.

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