Cracking assessment in concrete structures by distributed optical fiber

In this paper, a method to obtain crack initiation, location and width in concrete structures subjected to bending and instrumented with an optical backscattered reflectometer (OBR) system is proposed. Continuous strain data with high spatial resolution and accuracy are the main advantages of the OBR system. These characteristics make this structural health monitoring technique a useful tool in early damage detection in important structural problems. In the specific case of reinforced concrete structures, which exhibit cracks even in-service loading, the possibility to obtain strain data with high spatial resolution is a main issue. In this way, this information is of paramount importance concerning the durability and long performance and management of concrete structures. The proposed method is based on the results of a test up to failure carried out on a reinforced concrete slab. Using test data and different crack modeling criteria in concrete structures, simple nonlinear finite element models were elaborated to validate its use in the localization and appraisal of the crack width in the testing slab.Peer ReviewedPostprint (author’s final draft

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

Static and dynamic weighing of rolling stocks by mean of a customized FBG-Sensorized-Patch

The structural health monitoring (SHM) of an infrastructure is of fundamental importance for the structure and people safety. Fiber Bragg Grating (FBG) sensors allow to design for each application, a tailored array of quasi-distributed sensors integrated to the infrastructure. To ensure the structural integrity of the railways is crucial to verify that the infrastructures comply with safety requirements to carry out their task. Railways rolling stock must comply with speed limits, the maximum number of wagons, maximum weight limit distributed on each axis of the wagons and the allowed number of trains on specific routes. The identification of the vertical load acting on each wheel is fundamental for the safety of a rolling-stock moving on a railway line. This paper presents the results of a test campaign on sensitive smart patches for static and dynamic weighing of trains. The system aims to generate a gripping system based on the magnetic force of a plastoferrite patch, taking advantage of the peculiarity that the rails are made of ferritic steel. This solution has the benefit of simplifying and speeding up the installation process and enabling a fast and easy removal or change in the configuration of the sensors array on the rail

Fiber-Optic Strain-Based Deflection and Twist Sensing for a High-Aspect-Ratio Swept Wing

Designs of aircraft structures have been moving toward leaner, lightweight designs for increased fuel efficiency. The Passive Aeroelastic Tailored (PAT) wing developed under the NASA Advanced Air Transport Technology (AATT) project is an example of a swept-wing design with high aspect ratio that incorporates lightweight highly-flexible tailored composite construction. The passive aeroelastic tailored structural design has explored the design space to enable aeroelastically tailored wing structures to increase aspect ratios (from 9 to 14) and ultimately reduce weight by 20 percent to 25 percent without impacting aeroelastic performance. To further study the aeroelastic performance of such a wing, the NASA Armstrong Flight Research Center (AFRC) (Edwards, California) has developed efficient real-time structural algorithms that are used in conjunction with a fiber-optic measurement system for lightweight vehicle applications. The AFRC Fiber Optic Sensing System (FOSS) provides up to 8,000 distributed surface strain measurements at one-half-inch increments and can be used to estimate a variety of structural parameters such as shape and load. This report discusses the implementation of strain-based displacement and twist-sensing techniques applied to the PAT wing test article tested at the NASA AFRC Flight Loads Laboratory. Empirical FOSS strain data are collected under varying loading conditions. Strain data are processed with the displacement and twist-sensing algorithms and independently verified by comparison to conventional ground-based instrumentation

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

Embedding of optical interconnections in flexible electronics

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Application of distributed optical fiber sensors for the health monitoring of two real structures in Barcelona

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Structure and Infrastructure Engineering on 2018, available online at: http://www.tandfonline.com/10.1080/15732479.2018.1438479The versatility and ease of installation of Distributed Optical Fibre Sensors (DOFS) compared with traditional monitoring systems are important characteristics to consider when facing the Structural Health Monitoring (SHM) of real world structures. The DOFS used in this study provide continuous (in space) strain data along the optical fibre with high spatial resolution. The main issues and results of two different existing structures monitored with DOFS, are described in this paper. The main SHM results of the rehabilitation of an historical building used as hospital and the enlargement of a pre-stressed concrete bridge are presented. The results are obtained using a novel DOFS based on an Optical Backscattered Reflectometry (OBR) technique. The application of the optical fibre monitoring system to two different materials (masonry and concrete) provides also important insights on the great possibilities of this technique when monitoring existing structures. In fact, the influence of strain transfer between the DOFS and the bonding surface is one of the principal effects that should be considered in the application of the OBR technique to real structures. Moreover, and because structural surfaces generally present considerable roughness, the procedure to attach the optical fibre to the two monitored structures is described.Peer ReviewedPostprint (author's final draft

A multisensing setup for the intelligent tire monitoring

The present paper offers the chance to experimentally measure, for the first time, the internal tire strain by optical fiber sensors during the tire rolling in real operating conditions. The phenomena that take place during the tire rolling are in fact far from being completely understood. Despite several models available in the technical literature, there is not a correspondently large set of experimental observations. The paper includes the detailed description of the new multi-sensing technology for an ongoing vehicle measurement, which the research group has developed in the context of the project OPTYRE. The experimental apparatus is mainly based on the use of optical fibers with embedded Fiber Bragg Gratings sensors for the acquisition of the circumferential tire strain. Other sensors are also installed on the tire, such as a phonic wheel, a uniaxial accelerometer, and a dynamic temperature sensor. The acquired information is used as input variables in dedicated algorithms that allow the identification of key parameters, such as the dynamic contact patch, instantaneous dissipation and instantaneous grip. The OPTYRE project brings a contribution into the field of experimental grip monitoring of wheeled vehicles, with implications both on passive and active safety characteristics of cars and motorbikes