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Guidelines for Structural Health Monitoring

This chapter summarizes the state of the art and current developments of guidelines for structural health monitoring (SHM) and performance control. Technical guidelines and standards for condition monitoring and technical diagnostics of rotary machines and for non-destructive testing are not reviewed in this chapter.

How to reliably measure composite-embedded fibre Bragg grating sensors influenced by transverse and point-wise deformations?

Embedded conventional fibre Bragg grating (FBG) sensors with acrylate coating have been chosen for monitoring novel textile-reinforced composite materials with a complicated wavy structure as a result of reinforcing textures. Problems of monitoring this type of material occur due to the harsh fabrication technology of the composite and its complicated structure. Embedded fibre sensors are exposed to the influence of transverse and point-wise deformations. To what extent will these effects influence the measurement signal of a sensor? Temperature cycles, tension and vibration tests were carried out to answer this question. Transverse and point-wise deformation and micromechanical indentation tests on non-embedded FBG sensors were carried out to clarify the reliability of recorded signals.

Structural Health Monitoring by Distributed Fiber Optic Sensors Embedded into Technical Textiles

Abstract Technical textiles with embedded distributed fiber optic sensors have been developed for the purposes of structural health monitoring in geotechnical and civil engineering. The distributed fiber optic sensors are based on Brillouin scattering in silica optical fibers and OTDR in polymer optical fibers. Such “smart” technical textiles are used for reinforcement of geotechnical and masonry structures. The embedded fiber optic sensors provide online information about the condition of the structure and about the occurrence and location of any damage or degradation. Zusammenfassung Technische Textilien mit integrierten faseroptischen Sensoren eröffnen neue Möglichkeiten der Zustandsüberwachung (structural health monitoring) in Geotechnik und Ingenieurbau. Die verteilt messenden Sensoren basieren auf der Brillouin-Streuung in Glasfasern und auf der OTDR in polymeroptischen Fasern. Derartige “intelligente” technische Textilien werden in erster Line zur Verstärkung von geotechnischen Bauwerken und von Gebäuden genutzt. Die integrierten Sensoren liefern eine zeitnahe Information über den bestimmungsgemäßen Zustand des Bauwerks sowie über die Entstehung und den Ort von lokalen Bauwerksschäden.

Standardization in fiber-optic sensing for structural safety: activities in the ISHMII and IEC

Fiber-optic sensors are increasingly established in the sensor market. Their advantages have unquestionably been verified by numerous demonstrations to enhance the operational performance of aged structures or to monitor the structural behavior of safety-relevant structures or their components. However, there are some barriers in use due to a lack of extensive standardization of fiber-optic sensors. This leads very often to restraints in the user’s community. The paper shows the status in international standardization of fiber-optic sensors as well as current activities in leading institutions such as IEC and ISHMII and others with the purpose of providing relevant standards for a broader use of selected fiber-optic sensor technologies.

Principles, Concepts and Assessment of Structural Health Monitoring

This chapter introduces and describes the concept of structural health monitoring (SHM) to engineers and designers of technical structures, and to the owners/operators of such structures. It formulates general principles for integrating and implementing measurement and signal processing technologies in the context of SHM to diagnose the condition, performance and health of a technical structure. Information and recommended methods for designing instrumentation, data acquisition, data processing and data analysis for any SHM application are offered.

Performance Control: Nondestructive Testing and Reliability Evaluation

The performance of materials – as constituents of the components of engineering systems – is essential for the functionality of engineering systems in all branches of technology and industry. Instrumental for characterizing the performance of materials are 1. methods to study and assess the basic damage mechanisms that detrimentally influence the proper functioning of materials, such as materials fatigue and fracture (Chap. 7), corrosion (Chap. 12), friction and wear (Chap. 13), biogenic impact (Chap. 14), materials–environment interactions (Chap. 15) 2. methods to study and assess the performance of materials in engineering applications and to support condition monitoring of materialsʼ functional behavior. In this chapter the following experimental and theoretical methods for performance control and condition monitoring are compiled. Nondestructive evaluation (NDE) methods Methods of industrial radiology Methods of computed tomography (CT) Embedded sensors techniques to monitor structural health and to assess materials performance in situ under application conditions Methods to characterize the reliability of materials with statistical tools and test strategies for structural components and complex engineering systems.

Applications of Polymer Optical Fibers

The polymer optical fiber has been employed for many years now. In lighting technology it represents a widely used and recognized medium. The share of POF in sensor technology and data communications on the other hand is rather small. Up until now POF was predominately used in niche areas. At present a dramatic change is taking place especially in data communications. The digitalization of diverse entertainment media (music, language, video, pictures), a process which is practically completed, and the steadily growing amount of terminal equipment has led to a massive demand for reasonably priced, fast and reliable data connections in all areas of private and public life. In this chapter some possible uses for POF, as well as areas in which it is already being utilized, will be discussed. Those areas of use which lie outside the field of data communications and beyond the scope of this book will only be treated briefly. For these areas we refer to existing publications ([Wei98], [FOP97]).

Polymer optical fibers in Germany: reliability test for use in premises wiring

Progresses in fiber technology - low NA fibers, graded index fibers, perfluorinated fibers of extremely low attenuation - let expect that polymer fibers find their way from in-house wiring outside to the premise and moreover to the access network. In order to study the application range of these fibers a long term reliability test at different temperatures and humidity conditions has been initialized. This contains an accelerated lifetime test in order to separate thermal activated processes from those of different origin. Different environmental conditions will be simulated, especially adverse ones.The experiments are planned as a round robin test and can possibly contribute to a new concept of standard specification.

Results in standardization of FOS to support the use of SHM systems

Measurement and data recording systems are important parts of a holistic Structural Health Monitoring (SHM) system. New sensor technologies such as fiber-optic sensors are often used; however, standards (or at least guidelines) are not yet available or internationally approved. This lack in standardization makes the acceptance of FOS technologies in complex SHM systems substantially difficult. A standard family for different FOS technologies is therefore being developed that should help to design SHM systems in an optimal way. International standardization activities take place in several standardization bodies such as IEC and ASTM, and within SHM societies such as ISHMII. The paper reports on activities in standardization of fiber-optic sensors, on results already achieved, and on newly started projects. Combined activities of fiber sensor experts and SHM experts from Civil Engineering are presented. These contributions should help owners of structures as well as developers of sensors and monitoring systems to select effective and validated sensing technologies. Using these standards, both parties find recommendations how to proceed in development of SHM systems to evaluate the structural behavior based on e.g. standardized fiber optic sensors, and to derive necessary measures, e.g. the optimal maintenance strategy.

Messgrößen und Messverfahren

Die Messgrosen und Messverfahren der Technik basieren auf dem Internationalen Einheitensystem sowie auf geeigneten Aufnehmer- und Sensorprinzipien.