Smart PZT-interface for wireless impedance-based prestress-loss monitoring in tendon-anchorage connection

Khac-Duy Nguyen,김정태 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.9 No.6

For the safety of prestressed structures such as cable-stayed bridges and prestressed concrete bridges, it is very important to ensure the prestress force of cable or tendon. The loss of prestress force could significantly reduce load carrying capacity of the structure and even result in structural collapse. The objective of this study is to present a smart PZT-interface for wireless impedance-based prestress-loss monitoring in tendon-anchorage connection. Firstly, a smart PZT-interface is newly designed for sensitively monitoring of electro-mechanical impedance changes in tendon-anchorage subsystem. To analyze the effect of prestress force, an analytical model of tendon-anchorage is described regarding to the relationship between prestress force and structural parameters of the anchorage contact region. Based on the analytical model, an impedance-based method for monitoring of prestress-loss is conducted using the impedance-sensitive PZT-interface. Secondly,wireless impedance sensor node working on Imote2 platforms, which is interacted with the smart PZTinterface, is outlined. Finally, experiment on a lab-scale tendon-anchorage of a prestressed concrete girder is conducted to evaluate the performance of the smart PZT-interface along with the wireless impedance sensor node on prestress-loss detection. Frequency shift and cross correlation deviation of impedance signature are utilized to estimate impedance variation due to prestress-loss.

Wireless Impedance Sensor with PZT-Interface for Prestress-Loss Monitoring in Prestressed Concrete Girder

Khac-Duy Nguyen,So-Young Lee,Jeong-Tae Kim 한국비파괴검사학회 2011 한국비파괴검사학회지 Vol.31 No.6

Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.

Damage detection in beam-type structures via PZT’s dual piezoelectric responses

Khac-Duy Nguyen,김정태,Duc-Duy Ho 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.11 No.2

In this paper, practical methods to utilize PZT’s dual piezoelectric effects (i.e., dynamic strain and electro-mechanical (E/M) impedance responses) for damage detection in beam-type structures are presented. In order to achieve the objective, the following approaches are implemented. Firstly, PZT material’s dual piezoelectric characteristics on dynamic strain and E/M impedance are investigated. Secondly, global vibration-based and local impedance-based methods to detect the occurrence and the location of damage are presented. Finally, the vibration-based and impedance-based damage detection methods using the dual piezoelectric responses are evaluated from experiments on a lab-scaled beam for several damage scenarios. Damage detection results from using PZT sensor are compared with those obtained from using accelerometer and electric strain gauge.

Smart PZT-interface for wireless impedance-based prestress-loss monitoring in tendon-anchorage connection

Nguyen, Khac-Duy,Kim, Jeong-Tae Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.9 No.6

For the safety of prestressed structures such as cable-stayed bridges and prestressed concrete bridges, it is very important to ensure the prestress force of cable or tendon. The loss of prestress force could significantly reduce load carrying capacity of the structure and even result in structural collapse. The objective of this study is to present a smart PZT-interface for wireless impedance-based prestress-loss monitoring in tendon-anchorage connection. Firstly, a smart PZT-interface is newly designed for sensitively monitoring of electro-mechanical impedance changes in tendon-anchorage subsystem. To analyze the effect of prestress force, an analytical model of tendon-anchorage is described regarding to the relationship between prestress force and structural parameters of the anchorage contact region. Based on the analytical model, an impedance-based method for monitoring of prestress-loss is conducted using the impedance-sensitive PZT-interface. Secondly, wireless impedance sensor node working on Imote2 platforms, which is interacted with the smart PZT-interface, is outlined. Finally, experiment on a lab-scale tendon-anchorage of a prestressed concrete girder is conducted to evaluate the performance of the smart PZT-interface along with the wireless impedance sensor node on prestress-loss detection. Frequency shift and cross correlation deviation of impedance signature are utilized to estimate impedance variation due to prestress-loss.

Damage detection in beam-type structures via PZT's dual piezoelectric responses

Nguyen, Khac-Duy,Ho, Duc-Duy,Kim, Jeong-Tae Techno-Press 2013 Smart Structures and Systems, An International Jou Vol.11 No.2

In this paper, practical methods to utilize PZT's dual piezoelectric effects (i.e., dynamic strain and electro-mechanical (E/M) impedance responses) for damage detection in beam-type structures are presented. In order to achieve the objective, the following approaches are implemented. Firstly, PZT material's dual piezoelectric characteristics on dynamic strain and E/M impedance are investigated. Secondly, global vibration-based and local impedance-based methods to detect the occurrence and the location of damage are presented. Finally, the vibration-based and impedance-based damage detection methods using the dual piezoelectric responses are evaluated from experiments on a lab-scaled beam for several damage scenarios. Damage detection results from using PZT sensor are compared with those obtained from using accelerometer and electric strain gauge.

Wireless Impedance-Based SHM for Bolted Connections via Multiple PZT -Interfaces

Khac-Duy Nguyen,Jeong-Tae Kim 한국비파괴검사학회 2011 한국비파괴검사학회지 Vol.31 No.3

This study presents a structural health monitoring (SHM) method for bolted connections by using multi-channel wireless impedance sensor nodes and multiple PZT-interfaces. To achieve the objective, the following approaches are implemented. Firstly, a PZT-interface is designed to monitor bolt loosening in bolted connection based on variation of electro-mechanical(EM) impedance signatures. Secondly, a wireless impedance sensor node is designed for autonomous, cost-efficient and multi-channel monitoring. For the sensor platform, Imote2 is selected on the basis of its high operating speed, low power requirement and large storage memory. Finally, the performance of the wireless sensor node and the PZT-interfaces is experimentally evaluated for a bolt-connection model. Damage monitoring method using root mean square deviation(RMSD) index of EM impedance signatures is utilized to estimate the strength of the bolted joint.

Numerical Simulation of Electro-Mechanical Impedance Response in Cable-Anchor Connection Interlace

Nguyen, Khac-Duy,Kim, Jeong-Tae The Korean Society for Nondestructive Testing 2011 한국비파괴검사학회지 Vol.31 No.1

In this study, a finite element(FE) analysis on electro-mechanical impedance response of cable-anchor connection interface under various anchor force is presented. In order to achieve the objective, the following approaches are implemented. Firstly, an interface washer coupled with piezoelectric(PZT) material is designed for monitoring cable-force loss. The interface washer is a small aluminum plate on which a PZT patch is surface-bonded. Cable-force loss could be monitored by installing the interface washer between the anchor plate and the anchorage of cable-anchor connection and examining the changes of impedance of the interface washer. Secondly, a FE model for cable-anchor connection is established to examine the effect of cable-force on impedance response of interface washer. Also, the effects of geometrical and material properties of the interface washer on impedance responses under various cable-forces are investigated. Finally, validation of the FE analysis is experimentally evaluated by a lab-scale cable-anchor connection.

Imote2 기반 스마트 센서 노드를 통한 장대 사장교의 구조건전성 모니터링

Nguyen, Khac Duy,Ho, Duc Duy,이포영,김정태 한국구조물진단유지관리학회 2011 한국구조물진단학회 학술발표회논문집 Vol.2011 No.9

In this study, a field evaluation of Imote2-based smart sensor nodes for SHM of a full-scale cable-stayed bridge is presented. Firstly, the design of Imote2-based smart sensor nodes is described for vibration-based SHM. In the design, a solar-powered harvesting system is integrated for the autonomous operation of the sensor nodes. Secondly, the performance of the Imote2-based smart sensor nodes is evaluated for a full-scale cable stayed bridge. For field experiment, Hwamyeong Grand Bridge crossing Nakdong river between Busan and Gimhae, Korea, is selected as a target structure. The feasibility of the smart sensor nodes is evaluated by examining structural responses, sensor working status, and environmental factors under long-term ambient conditions.

Imote2/SHM-DAQ 센서노드와 PZT 센서를 이용한 케이블 장력 모니터링

Nguyen Khac Duy,Ho Duc Duy,김정태 한국구조물진단유지관리학회 2012 한국구조물진단학회 학술발표회논문집 Vol.2012 No.1

This study presents a method to monitor cable force using an Imote2/SHM-DAQ sensor node and a PZT sensor. The following approaches are carried out to achieve the objective. Firstly, the principle of piezoelectric material (e.g., PZT) as a strain sensor is reviewed. According to its piezoelectric features, the use of PZT sensor for strain measurement of a stay cable is presented. Secondly, the design of the data acquisition sensor node Imote2/SHM-DAQ is described. The sensor node is used to monitor strain-induced voltage from the PZT sensor. The advantages of the system are cheap, and enable for wireless communication and automated operation. Finally, the feasibility of the sensing system is evaluated on a lab-scale stay cable.

EM Impedance-based Tension Monitoring of Cable-Anchorage in Mooring System of Offshore Structure

Khac-Duy Nguyen,Po-Young Lee,Jeong-Tae Kim 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6

For offshore structure moored by cable system, the stability of the structure is dependent on tensile force of the cables. The loss of cable force may result in large displacement and unbalance of the structure. This study presents an electromechanical impedance-based method for tension monitoring of cable-anchorage in mooring system of offshore structure. In order to achieve the objective, the following approaches are implemented. Firstly, an PZT-Interface is introduced to monitor tensile force of cable. Once installed into the cable-anchorage, the PZT-interface works like a cantilever plate with imperfectly fixed boundary. The loss of cable force is represented by the weakness of the fixed boundary. Secondly, the variations of electromechanical (EM) impedance of the PZT-interface due to the variations of cable force are investigated. Several index like root mean square deviation, correlation coefficient deviation and frequency shift are utilized to capture these changes. Finally, the feasibility of the method is evaluated on a lab-scale cable-anchorage model.