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"Health monitoring (engineering)"
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An Experimental Study on the Effect of Temperature on Piezoelectric Sensors for Impedance-Based Structural Health Monitoring
The electromechanical impedance (EMI) technique is considered to be one of the most promising methods for developing structural health monitoring (SHM) systems. This technique is simple to implement and uses small and inexpensive piezoelectric sensors. However, practical problems have hindered its application to real-world structures, and temperature effects have been cited in the literature as critical problems. In this paper, we present an experimental study of the effect of temperature on the electrical impedance of the piezoelectric sensors used in the EMI technique. We used 5H PZT (lead zirconate titanate) ceramic sensors, which are commonly used in the EMI technique. The experimental results showed that the temperature effects were strongly frequency-dependent, which may motivate future research in the SHM field.
Journal Article
Value of information: impact of monitoring on decision-making
SUMMARYStructural health monitoring (SHM) is a process aimed at providing accurate and in‐time information concerning structural health condition and performance, which can serve as an objective basis for decision‐making regarding operation, maintenance, and repair. However, at the current state of practice, SHM is less used on real structures, and one reason for this is the lack of understanding of the Value of Information obtained from SHM. Consequently, even when SHM is implemented, bridge managers often make decisions based on experience or common sense, frequently considering with reserve and sometimes disregarding the suggestions arising from SHM. Managers weigh the SHM results based on their prior perception of the state of the structure and the confidence that they have in the specific applied SHM system and then make decisions considering the perceived effects of the actions they can undertake. In order to address and overcome the aforementioned identified limitations in the use of the SHM, a rational framework for assessment of the impact of the SHM on decision‐making is researched and proposed in this paper. The framework is based on the concept of Value of Information and demonstrated on the case study of the Streicker Bridge, a new pedestrian bridge on Princeton University campus. Copyright © 2013 John Wiley & Sons, Ltd.
Journal Article
SMC structural health monitoring benchmark problem using monitored data from an actual cable-stayed bridge
A structural health monitoring (SHM) system provides an efficient way to diagnose the condition of critical and large‐scale structures such as long‐span bridges. With the development of SHM techniques, numerous condition assessment and damage diagnosis methods have been developed to monitor the evolution of deterioration and long‐term structural performance of such structures, as well as to conduct rapid damage and post‐disaster assessments. However, the condition assessment and the damage detection methods described in the literature are usually validated by numerical simulation and/or laboratory testing of small‐scale structures with assumed deterioration models and artificial damage, which makes the comparison of different methods invalid and unconvincing to a certain extent. This paper presents a full‐scale bridge benchmark problem organized by the Center of Structural Monitoring and Control at the Harbin Institute of Technology. The benchmark bridge structure, the SHM system, the finite element model of the bridge, and the monitored data are presented in detail. Focusing on two critical and vulnerable components of cable‐stayed bridges, two benchmark problems are proposed on the basis of the field monitoring data from the full‐scale bridge, that is, condition assessment of stay cables (Benchmark Problem 1) and damage detection of bridge girders (Benchmark Problem 2). For Benchmark Problem 1, the monitored cable stresses and the fatigue properties of the deteriorated steel wires and cables are presented. The fatigue life prediction model and the residual fatigue life assessment of the cables are the foci of this problem. For Benchmark Problem 2, several damage patterns were observed for the cable‐stayed bridge. The acceleration time histories, together with the environmental conditions during the damage development process of the bridge, are provided. Researchers are encouraged to detect and to localize the damage and the damage development process. All the datasets and detailed descriptions, including the cable stresses, the acceleration datasets, and the finite element model, are available on the Structural Monitoring and Control website (http://smc.hit.edu.cn). Copyright © 2013 John Wiley & Sons, Ltd.
Journal Article
Thermal, Electrical and Surface Hydrophobic Properties of Electrospun Polyacrylonitrile Nanofibers for Structural Health Monitoring
This paper presents an idea of using carbonized electrospun Polyacrylonitrile (PAN) fibers as a sensor material in a structural health monitoring (SHM) system. The electrospun PAN fibers are lightweight, less costly and do not interfere with the functioning of infrastructure. This study deals with the fabrication of PAN-based nanofibers via electrospinning followed by stabilization and carbonization in order to remove all non-carbonaceous material and ensure pure carbon fibers as the resulting material. Electrochemical impedance spectroscopy was used to determine the ionic conductivity of PAN fibers. The X-ray diffraction study showed that the repeated peaks near 42° on the activated nanofiber film were α and β phases, respectively, with crystalline forms. Contact angle, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were also employed to examine the surface, thermal and chemical properties of the carbonized electrospun PAN fibers. The test results indicated that the carbonized PAN nanofibers have superior physical properties, which may be useful for structural health monitoring (SHM) applications in different industries.
Journal Article
Development and application of a relative displacement sensor for structural health monitoring of composite bridges
Summary This paper proposes a relative displacement sensor developed to measure directly the relative slip between slab and girder in composite bridges for assessing the health condition of shear connections. The structure, design principle, features, and calibration of the developed relative displacement sensor are presented. The design of the sensor ensures that there are no voltage outputs for the tension, compression, bending, and torsion effects, but only for the relative displacement between the two connecting pads of the sensor. The accuracy of the developed sensor in measuring the relative displacement response and using it for monitoring the conditions of shear connectors was tested on a composite bridge model in the laboratory. Shear connection condition was monitored under ambient vibrations, then static load tests were conducted to introduce cracks into the composite bridge. Both the vertical deflections and relative displacements were used for the crack detection. Experimental studies demonstrate that the developed sensor is very sensitive to the relative displacement and has a decent performance for the structural health monitoring of composite bridges. Copyright © 2014 John Wiley & Sons, Ltd.
Journal Article
A Noncontact FMCW Radar Sensor for Displacement Measurement in Structural Health Monitoring
This paper investigates the Frequency Modulation Continuous Wave (FMCW) radar sensor for multi-target displacement measurement in Structural Health Monitoring (SHM). The principle of three-dimensional (3-D) displacement measurement of civil infrastructures is analyzed. The requirements of high-accuracy displacement and multi-target identification for the measuring sensors are discussed. The fundamental measuring principle of FMCW radar is presented with rigorous mathematical formulas, and further the multiple-target displacement measurement is analyzed and simulated. In addition, a FMCW radar prototype is designed and fabricated based on an off-the-shelf radar frontend and data acquisition (DAQ) card, and the displacement error induced by phase asynchronism is analyzed. The conducted outdoor experiments verify the feasibility of this sensing method applied to multi-target displacement measurement, and experimental results show that three targets located at different distances can be distinguished simultaneously with millimeter level accuracy.
Journal Article
Compressive sensing-based lost data recovery of fast-moving wireless sensing for structural health monitoring
Summary Wireless sensor technology‐based structural health monitoring (SHM) has been widely investigated recently. This paper proposes a fast‐moving wireless sensing technique for the SHM of bridges along a highway or in a city in which the wireless sensor nodes are installed on the bridges to automatically acquire data, and a fast‐moving vehicle with an onboard wireless base station periodically collects the data without interrupting traffic. For the fast‐moving wireless sensing technique, the reliable wireless data transmission between the sensor nodes and the fast‐moving base station is one of the key issues. In fast‐moving states, the data packet loss rates during wireless data transmission between the moving base station and the sensor nodes will increase remarkably. In this paper, the data packets loss in the fast‐moving states is first investigated through a series of experiments. To solve the data packets loss problem, the compressive sensing (CS)‐based lost data recovery approach is proposed. A field test on a cable‐stayed bridge is performed to further illustrate the data packet loss in the fast‐moving wireless sensing technique and the ability of the CS‐based approach for lost data recovery. The experimental and field test results indicate that the Doppler effect is the main reason causing data packet loss for the fast‐moving wireless sensing technique, and the feasibility and efficiency of the CS‐based lost data recovery approach are validated Copyright © 2014 John Wiley & Sons, Ltd.
Journal Article
Features for damage detection with insensitivity to environmental and operational variations
This paper explores and compares the application of three different approaches to the data normalization problem in structural health monitoring (SHM), which concerns the removal of confounding trends induced by varying operational conditions from a measured structural response that correlates with damage. The methodologies for singling out or creating damage-sensitive features that are insensitive to environmental influences explored here include cointegration, outlier analysis and an approach relying on principal component analysis. The application of cointegration is a new idea for SHM from the field of econometrics, and this is the first work in which it has been comprehensively applied to an SHM problem. Results when applying cointegration are compared with results from the more familiar outlier analysis and an approach that uses minor principal components. The ability of these methods for removing the effects of environmental/operational variations from damage-sensitive features is demonstrated and compared with benchmark data from the Brite-Euram project DAMASCOS (BE97 4213), which was collected from a Lamb-wave inspection of a composite panel subject to temperature variations in an environmental chamber.
Journal Article