Review: optical fiber sensors for civil engineering applications

Optical fiber sensor (OFS) technologies have developed rapidly over the last few decades, and various types of OFS have found practical applications in the field of civil engineering. In this paper, which is resulting from the work of the RILEM technical committee “Optical fiber sensors for civil engineering applications”, different kinds of sensing techniques, including change of light intensity, interferometry, fiber Bragg grating, adsorption measurement and distributed sensing, are briefly reviewed to introduce the basic sensing principles. Then, the applications of OFS in highway structures, building structures, geotechnical structures, pipelines as well as cables monitoring are described, with focus on sensor design, installation technique and sensor performance. It is believed that the State-of-the-Art review is helpful to engineers considering the use of OFS in their projects, and can facilitate the wider application of OFS technologies in construction industry

Overview of sensors suitable for active flow control methods

Hlavným cieľom tejto bakalárskej práce bolo vytvorenie prehľadu vyvíjaných a už aplikovaných senzorov pre účely aktívneho riadenia prúdov. Senzory musia splňovať niektoré podmienky, preto výber senzorov bol naviazaný na reálnych výsledkoch testovacích programov, popis ktorých tvorí prvú časť tejto bakalárskej práce. Opis technológie a princíp fungovania senzorov je popísaný v druhej časti tejto práce.The main purpose of this bachelor thesis was to create the overview of the sensors developed for the future active flow control applications and overview the sensors already used in the active flow control applications. The sensors have to fulfil several requirements, so selection for the overview was based on the real flight test programs results, which were described in the first part of the thesis. The sensors technology description and operation principles were included in the second part of the thesis

Coaxial Cable Sensors and Sensing Instrument for Crack Detection in Bridge Structures -- Phase I: Field Qualification/Validation Planning

The objectives of this study are to pre-test analyze a decommissioned RC bridge that is selected in consultation with New York State Department of Transportation (NYSDOT), and design and plan the field tests of the bridge for the performance qualification and validation of distributed crack sensors and a fast Electrical Time Domain Reflectometry (ETDR) instrument to their full potential. The scope of work includes: (a) Selection of a decommissioned bridge, (b) Pre-test analysis of the select bridge structure to evaluate its progressive damage and determine the locations for sensor deployment, (c) Design and planning of field tests of the select bridge, (d) Field instrumentation with coaxial cable and fiber optical sensors for performance comparison, and (d) Summary of the findings of this study. Once fully validated and demonstrated in field conditions, distributed crack sensors and sensing instruments are expected to play a significant role in routine inspections and bridge ratings and in the rapid assessment of structural conditions for post-event evaluations and responses, improving the safety and security of transportation infrastructure at the height of a crisis. These roles are due primarily to their unique ability of permanently recording the widest crack a RC member experienced during a recent event. Such an attribute ensures the availability of damage data even if a fast ETDR system experiences malfunction during the event, greatly improving the reliability of bridge inspections

Advanced high temperature static strain sensor development

An examination was made into various techniques to be used to measure static strain in gas turbine liners at temperatures up to 1150 K (1600 F). The methods evaluated included thin film and wire resistive devices, optical fibers, surface acoustic waves, the laser speckle technique with a heterodyne readout, optical surface image and reflective approaches and capacitive devices. A preliminary experimental program to develop a thin film capacitive device was dropped because calculations showed that it would be too sensitive to thermal gradients. In a final evaluation program, the laser speckle technique appeared to work well up to 1150 K when it was used through a relatively stagnant air path. The surface guided acoustic wave approach appeared to be interesting but to require too much development effort for the funds available. Efforts to develop a FeCrAl resistive strain gage system were only partially successful and this part of the effort was finally reduced to a characterization study of the properties of the 25 micron diameter FeCrAl (Kanthal A-1) wire. It was concluded that this particular alloy was not suitable for use as the resistive element in a strain gage above about 1000 K

Pervasive Fibre-optic sensor networks in bridges: A UK case study

© 2018 Taylor & Francis Group, London. Integrating fibre-optic sensor networks in a newly-constructed infrastructure assets enables datadriven performance assessment during its construction and throughout its operational life. As part of a multimillion pound railway infrastructure redevelopment project, two new railway bridges were instrumented with an extensive network of both discrete (fibre Bragg gratings or FBGs) and distributed (based on Brillouin optical time domain reflectometry or BOTDR) fibre optic sensors to measure both strain and temperature throughout construction and in-service. Completed in 2016 in Staffordshire UK, both ‘self-sensing’ bridges contain more than 500 fibre Bragg grating sensors and over 600 metres of distributed fibre optic sensor cabling. This paper describes the sensing technologies employed, installation techniques for improving sensing robustness, the monitoring programme and objectives, data processing methods and assumptions, and the primary monitoring findings of this project. Results related to measurements of prestress losses in prestressed concrete girders, estimates of steel girder deflection using FBGs and videogrammetry, and assessments of percentage utilization of critical superstructure elements are presented. In terms of future directions, BIM-based environments which incorporate sensor elements and an emerging field of research known as Data-Centric Engineering are introduced as tools to better manage, maintain and learn from the information generated from self-sensing infrastructure.EPSRC, Innovate UK and the Lloyd's Register Foundation for funding this research through the Centre for Smart Infrastructure and Construction (CSIC) Innovation and Knowledge Centre and the Alan Turing Institute

Optical fiber sensors implementation for monitoring the early-age behavior of full-scale timber-concrete composite slabs

The study of the early-age behavior of Timber-Concrete Composite (TCC) structures is of great interest as it provides valuable information for manufacturing specification development, quality control, and optimization of the formwork design. In this study, the results of the continuous monitoring of the short-term behavior of TCC slabs using Brillouin Distributed Optical Fiber Sensors (DOFS) are reported. Two TCC slabs with 8.5 m of length were monitored. The composite elements are constituted of Cross-Laminated Timber (CLT) connected to a High-Performance Concrete (HPC) slab. During a monitoring period of about 30 days, the early-age temperature/strain variation in the fresh concrete and in the CLT slab was measured in great details by DOFS. From the presented results, the significant influence of the curing conditions on the early-age shrinkage was highlighted. It was also observed that creep and the daily hygrometric variations of environment affect considerably the composite action between the timber and the concrete. In addition, it was experimentally demonstrated that such mechanisms generate considerable structural changes in the composite elements even before their entry into service

Monitoring of new and existing stainless-steel reinforced concrete structures by clad distributed optical fibre sensing

The implementation of structural health monitoring systems in existing civil engineering structures could contribute to a safer and more resilient infrastructure as well as important savings. Due to their light weight, small size, and high resistance to the environment, distributed optical fibre sensors (DOFS) stand out as a very promising technology for damage detection and quantification in reinforced concrete structures. This dataset includes information of DOFS featuring an external polymeric cladding with rough surface, deployed in a stainless-steel reinforced concrete beam subjected to four-point bending. Several sensor positions, both embedded in the concrete and attached to the surface, are included in a multilayer configuration. The data of the sensors includes two series of test, first cyclic loading under service loads and lastly cyclic loading to failure. Additionally, data from Digital Image Correlation and the actuator recordings are included for cross-validation purposes

Index to NASA Tech Briefs, January - June 1966

Index to NASA technological innovations for January-June 196

Design and Technologies for a Smart Composite Bridge

An all-composite, smart bridge design for shortspan applications is described. The bridge dimensions are 9.14-m (30-ft.) long and 2.74-m (9-ft.) wide. A modular construction based on assemblies of pultruded fiber-reinforced-polymer (FRP) composite tubes is used to meet American Association of State Highway and Transportation Officials (AASHTO) H20 highway load ratings. The hollow tubes are 76 mm (3 in.) square and are made of carbon/vinyl-ester and glass/vinyl-ester. An extensive experimental study was carried out to obtain and compare properties (stiffness, strength, and failure modes) for a quarter portion of the full-sized bridge. The bridge response was measured for design loading, two-million-cycle fatigue loading, and ultimate load capacity. In addition to meeting H20 load criteria, the test article showed almost no reduction in stiffness or strength under fatigue loading and excellent linear elastic behavior up to failure. Fiber optic strain sensors were evaluated on the test article during testing. Sensor characteristics are determined as preparation for permanent field installation