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Showing papers in "Structural Health Monitoring-an International Journal in 2004"


Journal ArticleDOI
TL;DR: In this article, the state of the art in vibration-based condition monitoring with particular emphasis on structural engineering applications is reviewed, focusing on the use of in situ non-destructive sensing and analysis of system characteristics for detecting changes, which may indicate damage or degradation.
Abstract: Vibration based condition monitoring refers to the use of in situ non-destructive sensing and analysis of system characteristics –in the time, frequency or modal domains –for the purpose of detecting changes, which may indicate damage or degradation. In the field of civil engineering, monitoring systems have the potential to facilitate the more economical management and maintenance of modern infrastructure. This paper reviews the state of the art in vibration based condition monitoring with particular emphasis on structural engineering applications.

1,394 citations


Journal ArticleDOI
TL;DR: This paper describes a coherent strategy for intelligent fault detection which includes a taxonomy for the relevant concepts, a specification for operational evaluation which makes use of a hierarchical damage identification scheme, an approach to sensor prescription and optimisation and a data processing methodology based on a data fusion model.
Abstract: This paper describes a coherent strategy for intelligent fault detection. All of the features of the strategy are discussed in detail. These encompass: (i) a taxonomy for the relevant concepts, i.e. a precise definition of what constitutes a fault etc., (ii) a specification for operational evaluation which makes use of a hierarchical damage identification scheme, (iii) an approach to sensor prescription and optimisation and (iv) a data processing methodology based on a data fusion model.

355 citations


Journal ArticleDOI
TL;DR: In this paper, an embedded-ultrasonics structural radar (EUSR) is proposed for in situ nondestructive evaluation and structural health monitoring (SHM) of thin-wall structures.
Abstract: Embedded-ultrasonics structural radar (EUSR) is a new concept and methodology for in situ nondestructive evaluation (NDE) and structural health monitoring (SHM) of thin-wall structures. EUSR consists of: (a) an array of piezoelectric wafer active sensors (PWAS) embedded into the structure; and (b) electronic modules for signal transmission/reception, processing, and interpretation. EUSR utilizes guided elastic waves (Lamb waves) generated omnidirectionally into the thin-wall structure by surface-mounted permanently attached PWAS. The paper starts with the general concepts of the EUSR algorithm: transmission beamforming, reception beamforming, and time-of-fight (TOF) determination. Next, details of the Lamb wave generation with PWAS, verification of group-velocity dispersion curves, identification of optimal excitation frequency, and confirmation of wave front omnidirectionality are discussed. In the third part of the paper, the actual implementation of the EUSR method in a proof-of-concept demonstration i...

229 citations


Journal ArticleDOI
TL;DR: In this article, experimental aspects of dynamic response-based damage detection technique on carbon/ epoxy composites are addressed, where smart piezoelectric materials are used as sensors or actuators to acquire the curvature modes of structures.
Abstract: Many composite materials and structures are susceptible to defects, which can significantly reduce the strength of structures and may grow to failure. To avoid the catastrophic failure of structures, development of a reliable method of structural health monitoring is one of the most important keys in maintaining the integrity and safety of structures. Dynamic response-based damage detection offers a simple procedure as an alternative to the conventional nondestructive evaluation techniques. However, this technique depends on the quality of measured data for its identification accuracy. In this article, experimental aspects of dynamic response-based damage detection technique on carbon/ epoxy composites are addressed. Smart piezoelectric materials are used as sensors or actuators to acquire the curvature modes of structures. These materials are surface-bonded to the beams. An impulse hammer is used as an actuating source as well. Four types of damage detection algorithms are evaluated for several possible ...

133 citations


Journal ArticleDOI
TL;DR: In this paper, small piezoceramic patches have been selected for the generation and reception of the fundamental anti-symmetric Lamb mode, A0. The patches were distributed in a linear array in order for larger areas to be inspected.
Abstract: A first approach to a rapid and cost-effective health monitoring system for composite structures is presented. Relatively small piezoceramic patches have been selected for the generation and reception of the fundamental anti-symmetric Lamb mode, A0. The patches were distributed in a linear array in order for larger areas to be inspected. The propagation of Lamb waves was studied using Finite Element analysis and the optimal number and spacing of the transmitters was determined. Impact damage was successfully detected in multidirectional carbon fibre-reinforced plastic (CFRP) laminates using a very simple experimental set-up.

130 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented a novel approach to detect structural damage based on combining independent component analysis (ICA) extraction of time domain data and artificial neural networks (ANN) using a linear combination of dominant statistical independent components and the mixing matrix.
Abstract: This paper presents a novel approach to detect structural damage based on combining independent component analysis (ICA) extraction of time domain data and artificial neural networks (ANN) The advantage of using time history measurements is that the original vibration information is used directly However, the volume of data, measurement noise and the lack of reliable feature extraction tools are the major obstacles To circumvent them, the independent component analysis technique is applied to represent the measured data with a linear combination of dominant statistical independent components and the mixing matrix [A] Such a representation captures the essential structure of the measured vibration data The vibration features represented by the mixing matrix provide the relationship between the measured vibration response and the independent components and are then employed to build the simplified neural network model for damage detection Two examples are included to demonstrate the effectiveness of the method First, a truss structure with simulated displacement data was used, and the results show that healthy and damage states located in the nine elements may be classified Second, a bookshelf structure together with measured time history data from 24 piezoelectric single axis accelerometers was used to demonstrate the approach on a physical structure The results show the successful detection of the undamaged and damaged states with very good accuracy and repeatability

111 citations


Journal ArticleDOI
TL;DR: The results show that the probabilistic approach is able to successfully detect and locate the simulated damage involving stiffness loss in the braces of the analytical benchmark model based on simulated ambient-vibration data.
Abstract: A new two-step approach for probabilistic structural health monitoring is presented, which involves modal identification followed by damage assessment using the pre- and post-damage modal parameters based on a new Bayesian model updating algorithm. The new approach aims to attack the structural health monitoring problems with incomplete modeshape information by including the underlying full modeshapes of the system as extra random variables, and by employing the Expectation-Maximisation algorithm to determine the most probable parameter values. The non-concave non-linear optimisation problem associated with incomplete modeshape cases is converted into two coupled quadratic optimisation problems, so that the computation becomes simpler and more robust. We illustrate the new approach by analysing the Phase II Simulated Benchmark problems sponsored by the IASC-ASCE Task Group on Structural Health Monitoring. The results of the analysis show that the probabilistic approach is able to successfully detect and locate the simulated damage involving stiffness loss in the braces of the analytical benchmark model based on simulated ambient-vibration data.

85 citations


Journal ArticleDOI
TL;DR: In this article, a Kalman model is constructed by performing a stochastic subspace identification to fit the measured response histories of the undamaged (reference) structure, which will not be able to reproduce the newly measured responses when damage occurs.
Abstract: This paper presents an application of statistical process control techniques for damage diagnosis using vibration measurements. A Kalman model is constructed by performing a stochastic subspace identification to fit the measured response histories of the undamaged (reference) structure. It will not be able to reproduce the newly measured responses when damage occurs. The residual error of the prediction by the identified model with respect to the actual measurement of signals is defined as a damage-sensitive feature. The outlier statistics provides a quantitative indicator of damage. The advantage of the method is that model extraction is performed by using only the reference data and that no further modal identification is needed. On-line health monitoring of structures is therefore easily realized. When the structure consists of the assembly of several sub-structures, for which the dynamic interaction is weak, the damage may be located as the errors attain the maximum at the sensors instrumented in the ...

71 citations


Journal ArticleDOI
TL;DR: In this article, modal analysis techniques for locating damage in a wooden wall structure by evaluating damage sensitive parameters such as resonant pole shifts and mode shapes, residue and stiffness changes are presented.
Abstract: Vibration techniques have been employed for detecting the presence and monitoring the progression of damage in structures Pinpointing the location of damage is a more complicated and elaborate task This paper presents modal analysis techniques for locating damage in a wooden wall structure by evaluating damage-sensitive parameters such as resonant pole shifts and mode shapes, residue and stiffness changes Artificial damage (simulating termite degradation) was created in one of the walls of a specially constructed room The wall was excited using an impact hammer and its frequency response measured using a laser vibrometer Resonant poles (plotted in the s-plane) were used for identifying modes that are sensitive to damage, since not all modes are equally affected by the presence of damage The damaged region was identified by visual comparison of the deformation mode shapes before and after damage The modal residue and stiffness changes were also quantified for a better representation of the damage lo

70 citations


Journal ArticleDOI
TL;DR: In this paper, a delamination detection scheme for CF/EP composite laminates based on the Lamb wave propagation was proposed, where the fundamental symmetric Lamb mode (S0) and the delaminationinduced basic shear m...
Abstract: A delamination detection scheme for the CF/EP composite laminates based on the Lamb wave propagation was proposed. The fundamental symmetric Lamb mode (S0) and the delaminationinduced basic shear m...

68 citations


Journal ArticleDOI
TL;DR: In this article, a new sensor was designed based on the change in topology of its outer conductor under strain conditions instead of a change in geometry of a conventional cable sensor, which is used as distributed sensors to detect cracks or measure strains in reinforced concrete (RC) structures with the electrical time domain reflectometry (ETDR).
Abstract: Coaxial cables are used as distributed sensors to detect cracks or measure strains in reinforced concrete (RC) structures with the electrical time domain reflectometry (ETDR). An emphasis was placed on the development and validation of a type of novel cable sensors. The new sensor was designed based on the change in topology of its outer conductor under strain conditions instead of the change in geometry of a conventional cable sensor. Finite difference time domain (FDTM) models of four types of cables were established to understand the inter-relationship among various design parameters. They were calibrated with a standard displacement transducer in nine tension tests and then mounted near the surface of six RC beams of 0.91-m long to validate their sensitivity and performance. The bending test results of RC beams are in general agreement with those from the calibration test of cables. Both indicate that the proposed sensors are over 15-80 times more sensitive than sensors based on commercial coaxial cab...

Journal ArticleDOI
TL;DR: In this article, the authors report the feasibility of using embedded Fabry-Pe rot fiber optic sensors to detect and monitor the propagation of cracks and delamination within concrete beams induced by corrosion of the reinforcing bars.
Abstract: This paper reports the feasibility of using embedded Fabry–Pe rot fiber optic sensors to detect and monitor the propagation of cracks and delamination within concrete beams induced by corrosion of the reinforcing bars. In this research, four series of reinforced concrete beams were subjected to varying degrees of corrosion-induced damage by modifying the composition of the concrete mix and subjecting all specimens to the same accelerated corrosion environment. The concept employed in this study involves embedding the Fabry–Pe rot sensor between two reinforcing bars to measure the transverse tensile strains associated with the longitudinal crack along the reinforcing bars (and in severe cases, delamination of the concrete beam) resulting from the radial expansion of the corroding rebars. Excellent correlation was obtained between the Fabry–Pe rot strain data and the amount of steel loss resulting from accelerated corrosion. In addition, the optical sensor strain readings and the reductions in the load-carr...

Journal ArticleDOI
TL;DR: In this article, two different approaches, system identification and statistical pattern recognition, are summarised and applied in turn to vibration data collected from three scale model reinforced concrete bridges, and the results show that system identification paradigm can successfully locate and quantify the damage to the decks when they are loaded to incipient collapse, especially when experience is used to determine the parameters to use in the finite element updating procedure.
Abstract: This paper briefly outlines the rationale for structural health monitoring as an integral component of bridge management systems. Two different approaches, system identification and statistical pattern recognition, are summarised and applied in turn to vibration data collected from three scale modelreinforced concrete bridges. The results show that the system identification paradigm can successfully locate and quantify the damage to the decks when they are loaded to incipient collapse, especially when experience is used to determine the parameters to use in the finite element updating procedure. However, the study also demonstrated that this approach requires a large amount of high quality data, requirements that cannot always be met readily in the field. In contrast, although the statistical pattern recognition approach was not able to quantify or locate the damage, it was able to clearly indicate that damage had occurred from relatively few measurements. A comparison of the strengths and weaknesses of t...

Journal ArticleDOI
TL;DR: In this article, two residual generation schemes are proposed to monitor sensor faults, namely the modal filtering approach and the so-called Parity Space approach, which are then tested using a probabilistic approach using a 2 test to determine if there is a faulty sensor.
Abstract: Structures with a large number of sensors and actuators are becoming more common, and their applications vary from active control to damage location. This large amount of spatial information should be used to advantage to continuously monitor the correct functioning of the sensors during normal operation. Errors introduced by faulty sensors can cause a loss of performance and erroneous conclusions, and this paper analyses additive sensor faults. Two residual generation schemes are proposed to monitor sensor faults, namely the modal filtering approach and the so-called Parity Space approach. These residuals are then tested using a probabilistic approach using a 2 test to determine if there is a faulty sensor. These approaches are demonstrated on a simulated cantilevered beam excited at its tip and also on an experimental subframe structure.

Journal ArticleDOI
TL;DR: In this paper, a geometric representation of system dynamics can be used to extract information about a structure's response to sustained excitation, and various features of the geometric representation are used to describe the degree to which the dynamics have been altered by damage.
Abstract: Recent works by Nichols et al. (Nichols, J.M., Todd, M.D., Seaver, M. and Virgin, L.N. (2003). Use of chaotic excitation and attractor property analysis in structural health monitoring. Phys Rev E, 67(016209)) and Pecora et al. (Todd, M.D., Nichols, J.M., Pecora, L.M. and Virgin, L.N. (2001). Vibration-based damage assessment utilizing state-space geometry changes: Local attractor variance ratio. Smart Materials and Structures, 10, 1000-1008.) have shown that steady-state dynamic analysis of structural health exhibits advantages over transient vibrational analysis. A geometric representation of system dynamics can be used to extract information about a structure’s response to sustained excitation. Analysis of various features of the geometric representation can be used to describe the degree to which the dynamics have been altered by damage. Here, the feature we employ is the ‘‘continuity test,’’ a statistical test first described by Pecora et al. (Pecora, L.M., Carroll, T.L. and Heagy, J.F. (1997). Stati...

Journal ArticleDOI
TL;DR: In this article, a stochastic measure of fatigue crack damage in ductile alloys that are commonly encountered in structures and machinery components of complex mechanical systems such as land, air, ocean, and space vehicles is proposed.
Abstract: This paper models a stochastic measure of fatigue crack damage in ductile alloys that are commonly encountered in structures and machinery components of complex mechanical systems such as land, air, ocean, and space vehicles. The constitutive equations of the damage measure are built upon the physics of fracture mechanics and are substantiated by Karhunen-Loeve decomposition of fatigue test data where statistical orthogonality of the estimated measure and the resulting estimation error is demonstrated in a Hilbert space setting. The non-stationary probability distribution (PDF) function of the damage estimate is generated in a closed form without numerically solving stochastic differential equations in the Wiener integral or It ^ o integral setting. The model of crack damage measure allows real-time execution of decision algorithms for health monitoring, risk assessment, and life prediction of mechanical structures on inexpensive platforms such as a Pentium processor. The stochastic model of fatigue crack damage measure is in good agreement with experimental data sets for 2024-T3 and 7075-T6 aluminum alloys.

Journal ArticleDOI
TL;DR: In this article, a one-way reinforced concrete (RC) slab was subjected to short-duration concentrated impact load and its dynamic characteristic for the virgin and damaged conditions were studied using two signal processing techniques.
Abstract: A one-way reinforced concrete (RC) slab was subjected to short-duration concentrated impact load and its dynamic characteristic for the virgin and damaged conditions were studied using two signal processing techniques. The recorded strain and acceleration signals were analyzed using the Fast Fourier Transform (FFT) and the Hilbert Huang Transform (HHT). From these analyses, the percentage reductions in the modal frequency for varying degrees of damage (or magnitude of applied load) were obtained. Based on the eigen-solution of a 3-element partitioned beam model, the frequency–damage relationship was also estimated using the observed initial flexural stiffness of the half-cycle hysteresis path associated with each stage of applied load. Both semi-empirical and experimental results showed close agreement and a 30% frequency reduction was observed between the virgin state and yield. Three quarters of the total frequency reduction from virgin-to-yield occurred within an applied load range of 30% of the yield ...

Journal ArticleDOI
TL;DR: A classification system for damage detection that combines the discrete wavelet transform, a statistical methodology, and neural networks is proposed that can automatically classify a normal or faulty compressor.
Abstract: This paper proposes a classification system for damage detection that combines the discrete wavelet transform, a statistical methodology, and neural networks. In the proposed system, vibration signals of compressors are acquired as initial system inputs. The condition features are extracted by statistical moments of wavelet coefficients before entering the networks. The proposed on-line classification system can automatically classify a normal or faulty compressor. The system has been implemented to increase product reliability and reduce downtime for a large production facility.

Journal ArticleDOI
TL;DR: This paper reviews some popular criteria traditionally employed in model evaluation and indicates that Akaike Information Criterion (AIC) has superior performance.
Abstract: Model-based preventive maintenance relies on creating models that can either predict future operating states or upcoming failures directly. Since no modeling algorithm can guarantee a best solution in every situation, it becomes necessary to evaluate the solutions generated by these techniques. This paper reviews some popular criteria traditionally employed in model evaluation. Several evaluation criteria proposed in the literature are restricted in their applicability because of their assumptions about the modeling process/data. Some evaluation criteria are tested on two artificial data sets. The results from our tests indicate that Akaike Information Criterion (AIC) has superior performance. The conclusion has been used and verified in one industrial monitoring application.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a fracture monitoring system for sewer pipelines, which adopts fracture sensors made of fabric glass and carbon black-epoxy composite materials; a small embeddable terminal is included that can be connected to the Internet.
Abstract: Sewer pipeline breaks were reported after severe earthquakes like the great Hanshin-Awaji earthquake in 1995. Although sewer pipeline breakage is not an emergent problem, they may cause epidemic disasters if left unrepaired. However, it is extremely expensive to find damaged parts and very time consuming to visually inspect all sewer pipelines laid underground. This demands a low-cost fracture monitoring system for sewer pipelines. The present study proposes a new fracture monitoring system for sewer pipelines and explains its demonstration using a small sewer pipe. The fracture monitoring system adopts fracture sensors made of fabric glass and carbon black–epoxy composite materials; a small embeddable terminal is included that can be connected to the Internet. In the sensor, a carbon black sheet is sandwiched between a surface layer and a base layer: both are made from fabric glass–epoxy plies. A part of the glass fibre in the surface layer is cut perpendicular to the loading direction to make a crack st...

Journal ArticleDOI
TL;DR: In this article, the authors used transient stress waves to quantify the extent of damage in cylindrical structures and found that the attenuation of a stress wave which had traversed the bolts in the presence of increasing damage was observed.
Abstract: Transient stress waves have been used to quantify the extent of damage in cylindrical structures. In the present study, this technique is extended to the in situ quantification of damage in a bolt. Piezoelectric wafers were bonded to either end of two bolts, one of which was loaded in tension in a steel block. Both bolts were incrementally damaged by sawing a cut, to observe the changes in a stress wave which had traversed the bolts in the presence of increasing damage. A clear relationship between the extent of damage in the bolt and the attenuation of the stress wave was observed. Tension in the bolt did not affect this relationship, illustrating the in situ applicability of the technique.In a second set of experiments, bolts were subjected to conditions in which stress corrosion cracking would occur, whilst stress waves were excited in each bolt, to illustrate the ability of the method to detect a naturally occurring form of damage. It was found that the attenuation of a stress wave which had traversed...