Structural health monitoring

About: Structural health monitoring is a research topic. Over the lifetime, 11727 publications have been published within this topic receiving 186231 citations.

Cyclic Crack Monitoring of a Reinforced Concrete Column under Simulated Pseudo-Dynamic Loading Using Piezoceramic-Based Smart Aggregates

Abstract: Structural health monitoring is an important aspect of maintenance for bridge columns in areas of high seismic activity. In this project, recently developed piezoceramic-based transducers, known as smart aggregates (SA), were utilized to perform structural health monitoring of a reinforced concrete (RC) bridge column subjected to pseudo-dynamic loading. The SA-based approach has been previously verified for static and dynamic loading but never for pseudo-dynamic loading. Based on the developed SAs, an active-sensing approach was developed to perform real-time health status evaluation of the RC column during the loading procedure. The existence of cracks attenuated the stress wave transmission energy during the loading procedure and reduced the amplitudes of the signal received by SA sensors. To detect the crack evolution and evaluate the damage severity, a wavelet packet-based structural damage index was developed. Experimental results verified the effectiveness of the SAs in structural health monitoring of the RC column under pseudo-dynamic loading. In addition to monitoring the general severity of the damage, the local structural damage indices show potential to report the cyclic crack open-close phenomenon subjected to the pseudo-dynamic loading.

Cointegration: a novel approach for the removal of environmental trends in structural health monitoring data

Abstract: Before structural health monitoring (SHM) technologies can be reliably implemented on structures outside laboratory conditions, the problem of environmental variability in monitored features must be first addressed. Structures that are subjected to changing environmental or operational conditions will often exhibit inherently non-stationary dynamic and quasi-static responses, which can mask any changes caused by the occurrence of damage. The current work introduces the concept of cointegration , a tool for the analysis of non-stationary time series, as a promising new approach for dealing with the problem of environmental variation in monitored features. If two or more monitored variables from an SHM system are cointegrated, then some linear combination of them will be a stationary residual purged of the common trends in the original dataset. The stationary residual created from the cointegration procedure can be used as a damage-sensitive feature that is independent of the normal environmental and operational conditions.

Structural Monitoring with Fibre Optic Technology

Abstract: This is an ambitious book aimed at introducing the relatively new concepts and possibilities of optical fibre sensors for structural monitoring to the uninitiated who have an engineering or general physics background. Measures draws the reader into the volume with a description of smart structures - the structural monitoring equivalent of artificial nervous systems - before a series of back-to-basics tutorials on optical theory and photonic technology. The emphasis on smart structures early in the book is a worthy attention-grabber since it elevates the subject of structural health monitoring above just another set of techniques for making engineering measurements. The promise is to `revolutionize engineering design philosophy' by creating `intelligence within otherwise inanimate structures'. In the latter two thirds of the book, the author steps through the main issues of structural monitoring using fibre optic sensors. Intensity-based, interferometric, polarimetric and spectral sensors (including the ubiquitous Bragg grating) are compared and contrasted. The hot topic of strain versus temperature discrimination in fibre sensors earns a whole chapter and several useful techniques for overcoming this cross-sensitivity are portrayed. Installation of sensors is also discussed with reference to retro-fit and co-manufacturing (embedding) approaches. Examples of concrete constructions such as bridges (a frequent theme in the book) and fibre-reinforced plastics such as glass-fibre and carbon composite materials are considered. A chapter on `short-gauge' sensors and applications deals in some depth with the Bragg grating as a strain sensor. The methods of multiplexing and interrogating these devices are explored with many examples from both Measures' own research and the work of other groups worldwide. The Beddington Trail bridge trial in Calgary, one of the first such installations of Bragg gratings, followed by the more ambitious Confederation Bridge, also in Canada, provide concrete examples of the technology's application. The material is marred somewhat by the inferior reproduction of some of the photographs, especially those showing field installations of the optical sensors. Other applications are not neglected. A description of trials aboard a Norwegian Naval vessel with composite hull monitored by Bragg gratings is also given. Interferometric sensors in similar applications trials are also covered in chapters on short and long gauge length devices. Distributed strain and temperature sensing techniques using Fourier transform, low coherence and stimulated backscattering are covered in the penultimate chapter, which draws together distributed measurement at a small physical scale in the form of intra-Bragg grating strain profile measurements (on the scale of millimetres) and measurements over kilometres using stimulated Brillouin scattering. In this reviewer's opinion the book dwells on strain monitoring in civil engineering structures at the expense of a broader scope, which could have included, for example, the detection of impacts or the acoustic emissions from crack propagation and other forms of structural damage. Nevertheless, this volume is an impressive collection of background and examples of real applications in heavyweight engineering. It adds significantly to the claim that fibre optic sensors have at last arrived. Peter Foote

Development of adaptive modeling techniques for non-linear hysteretic systems

Abstract: Adaptive estimation procedures have gained significant attention by the research community to perform real-time identification of non-linear hysteretic structural systems under arbitrary dynamic excitations. Such techniques promise to provide real-time, robust tracking of system response as well as the ability to track time variation within the system being modeled. An overview of some of the authors’ previous work in this area is presented, along with a discussion of some of the emerging issues being tackled with regard to this class of problems. The trade-offs between parametric-based modeling and non-parametric modeling of non-linear hysteretic dynamic system behavior are discussed. Particular attention is given to (1) the effects of over- and under-parameterization on parameter convergence and system output tracking performance, (2) identifiability in multi-degree-of-freedom structural systems, (3) trade-offs in setting user-defined parameters for adaptive laws, and (4) the effects of noise on measurement integration. Both simulation and experimental results indicating the performance of the parametric and non-parametric methods are presented and their implications are discussed in the context of adaptive structures and structural health monitoring.

Recent advancements in the electromechanical (E/M) impedance method for structural health monitoring and NDE

Abstract: The emerging electro-mechanical impedance technology has high potential for in-situ health monitoring and NDE of structural systems and complex machinery. At first, the fundamental principles of the electro-mechanical impedance method are briefly reviewed and ways for practical implementation are highlighted. The equations of piezo- electric material response are given, and the coupled electro-mechanical impedance of a piezo-electric wafer transducer as affixed to the monitored structure is discussed. Due to the high frequency operation of this NDE method, wave propagation phenomena are identified as the primary coupling method between the structural substrate and the piezo-electric wafer transducer. Attention is then focused on several recent advancements that have extended the electro-mechanical impedance method into new areas of applications and/or have developed its underlying principles. US Army Construction Engineering Research Laboratory used the electro-mechanical impedance method to monitor damage development in composite overlaid civil infrastructure specimens under full-scale static testing. A simplified E/M impedance measuring technique was employed at the Polytechnic University of Madrid, Spain, to detect damage in GFRP composite specimens. The development of miniaturized `bare-bones' impedance analyzer equipment that could be easily packaged into transponder-size dimensions is being studied at the University of South Carolina. US Army Research Laboratory developed novel piezo-composite film transducers for embedment into composite structures. Disbond gauges for monitoring the structural joints of adhesively bonded rotor blades have been studies in the Mechanical Engineering Department at the University of South Carolina. These recent developments accentuate the importance and benefits of using the electro-mechanical impedance method for on-line health monitoring and damage detection in a variety of applications. Further investigation of the electro-mechanical impedance method is warranted. A further examination of the complex interaction between wave propagation, drive-point impedance, structural damage and electro-mechanical impedance of the piezo-electric wafer transducer is needed. Once these aspects are better understood, the E/M impedance method has the potential to become a widely used NDE technique with large applicability in diverse engineering fields (aerospace, automotive, infrastructure and biomedical implants).