Unbonded Portland Cement Concrete Overlay/Pavement Monitoring with Integrated Grating and Scattering Optical Fiber Sensors

This report summarizes the findings and results from a laboratory and field study on the strain distribution and crack development in 3 thick concrete panels cast on top of existing concrete pavements as a rapid rehabilitation strategy for roadways. Both fiber Bragg gratings (FBG) and Brillouin Optical Time Domain Reflectometry/Analysis (BOTDR/A) were applied and tested for their feasibility and effectiveness in distributed strain measurement and crack detection. For laboratory tests, six 6\u27×6 panels were cast similar to their corresponding field construction. Each was tested under both truck loads and under threepoint loads. The performance of distributed BOTDR/A strain measurements was compared with that of FBG sensors. In field study, the performance of FBG sensors was compared with that from strain gauges when the ambient temperature was measured with thermocouples. Overall, hairline to major cracks can be successfully detected with the distributed BOTDA measurements. The strain distributions measured from the FBG and BOTDR/A sensors are consistent. The FBG readings are in good agreement with those of strain gauges. Both FBG and BOTDR/A technologies are promising for pavement monitoring

Static and Fatigue Behavior of FRP-Reinforced Concrete Beams and an SHM System with Fiber Optic Sensors under Different Weathering Conditions

Structural Health Monitoring (SHM) techniques are often used for detecting damage and diagnosing the structural conditions. Fibre Optic Sensors (FOS) are found to be very accurate and durable for outdoor applications including embedment in reinforced concrete structures. However, there are many issues related to installation and constructability of SHM systems and in-situ installation of FOS on rebars in reinforced concrete (RC) elements, especially when Fibre Reinforced Polymer (FRP) bars are used as reinforcements. Here, a solution is provided for installation of a FOS strain sensor by mounting it on a supplementary bar a priori and then attaching it to the main reinforcing bar of interest at the construction site prior to concrete pouring. Such innovative deployment system for FOS is particularly advantageous for developing a practical SHM system for infrastructure. However, the performance of such systems under various loading and climatic conditions is not very well known. The objective of this research is to assess the performance of the said system used in concrete beams reinforced with FRP bars, under normal and adverse environmental conditions. A set of twelve specimens with and without exposure to various environmental conditions have been tested under static and fatigue loads to determine the effectiveness of the sensing system in these conditions. Apart from measuring the response quantities like strain and deformation, the Scanning Electron Microscopy (SEM) technique has been used to determine the effect of the adverse environmental conditions on the rebars. In addition, numerical modeling of the beams using the Finite Element Method (FEM) has been applied to carry out a parametric study on the effect of the properties of concrete and the bar sizes on the performance of the above sensing system. From the present study, it is observed that the proposed system works well in terms of capturing the strain under static and fatigue conditions in normal and adverse environmental conditions. However, the performance of the sensing system degrades in the case of alkaline immersion. The outdoor or wet and dry conditions do not affect the performance of the system

Testing of Materials and Elements in Civil Engineering

This book was proposed and organized as a means to present recent developments in the field of testing of materials and elements in civil engineering. For this reason, the articles highlighted in this editorial relate to different aspects of testing of different materials and elements in civil engineering, from building materials to building structures. The current trend in the development of testing of materials and elements in civil engineering is mainly concerned with the detection of flaws and defects in concrete elements and structures, and acoustic methods predominate in this field. As in medicine, the trend is towards designing test equipment that allows one to obtain a picture of the inside of the tested element and materials. Interesting results with significance for building practices were obtained

Active thermography for the investigation of corrosion in steel surfaces

The present work aims at developing an experimental methodology for the analysis of corrosion phenomena of steel surfaces by means of Active Thermography (AT), in reflexion configuration (RC). The peculiarity of this AT approach consists in exciting by means of a laser source the sound surface of the specimens and acquiring the thermal signal on the same surface, instead of the corroded one: the thermal signal is then composed by the reflection of the thermal wave reflected by the corroded surface. This procedure aims at investigating internal corroded surfaces like in vessels, piping, carters etc. Thermal tests were performed in Step Heating and Lock-In conditions, by varying excitation parameters (power, time, number of pulse, ….) to improve the experimental set up. Surface thermal profiles were acquired by an IR thermocamera and means of salt spray testing; at set time intervals the specimens were investigated by means of AT. Each duration corresponded to a surface damage entity and to a variation in the thermal response. Thermal responses of corroded specimens were related to the corresponding corrosion level, referring to a reference specimen without corrosion. The entity of corrosion was also verified by a metallographic optical microscope to measure the thickness variation of the specimens

In-situ deformation monitoring of aerospace qualified composites with embedded improved draw tower fibre Bragg gratings

Aerospace certified fibre reinforced plastics (FRPs) are extreme performing construction materials, which today are increasingly applied in primary structures of the new generation aircrafts (e.g. Boeing 787, Airbus 350, Bombardier C-Series), such as the fuselage, the wings and the fin. An interesting aspect on the technological point of view of sensing is that airplane manufacturers such as Airbus and Boeing are looking at incorporating health-monitoring systems (such as optical fibre sensors, especially fibre Bragg gratings) that will allow the airplane to self-monitor and report maintenance requirements to ground-based computer systems. However, one has to realize that the mechanical behaviour of anisotropic FRPs is significantly different compared to conventional isotropic construction materials. In this dissertation, the author focuses on monitoring the strain and (permanent) deformation in carbon reinforced plastic laminates with embedded fibre Bragg gratings. The research is divided in two main parts. In the first part of this research, the existing fibre draw tower technology is utilized, to manufacture an improved version of the existing in-line high quality, draw tower fibre Bragg gratings (DTG®s). With respect to accurate measurements and structural integrity, the research focuses on reducing the total diameter of the optical fibre, so the incorporation in the reinforcement fibres is enhanced and the distortion in the composite is reduced. The author elaborates in detail the methods of strain and temperature calibrations and the different setups which are applied. Additionally, with respect to the high temperatures during the composite manufacturing process, the thermal stability of the DTG®s is studied at elevated temperatures (>300°C). In the second part, the author embeds the DTG®s in specific types of thermoset and thermoplastic carbon reinforced plastic laminates. The author applies the embedded DTG®s in several stages of the composite lifetime. Starting with the monitoring of the composite manufacturing process and ending with fatigue testing until failure of the composite laminates. During the different experiments, the sensors are subjected to high temperatures, high pressures, extreme longitudinal strains and transverse strains and in the mean time, they are employed to very accurately measure (multi-axial) strains inside composites at microstrain level (~10 6)

Capteurs à fibre optique pour le monitorage des poutres en béton armé réhabilitées avec des matériaux composites

Plusieurs pays ont un grand besoin de réparer et renforcer leur infrastructure routière. Presque partout. Ie traffic a beaucoup dépassé les charges de design initial. Les pays nordiques connaissent des conditions hivernales extrêmes qui sont combinées avec l'utilisation de sels de déglaçage et qui accélère la détérioration de structures. Au Canada, l'état de détérioration force les gouvernements, dont les gouvernements fédéral et provinciaux, a envisager l'utilisation des polymères renforces de fibres (PRF) pour prolonger la durée de vie des structures existantes. Les matériaux innovateurs PRF utilises pour la réhabilitation des structures déficientes peuvent être facilement instrumentés avec des systèmes de monitorage. Les détecteurs intégrés pourront fournir des informations a propos de l'état des structures, une baisse en performance ou une défaillance majeure, optimisant ainsi leur durée de vie sans en compromettre la sécurité. Les capteurs a fibre optique (CFO) sont des nouveaux candidats pour Ie monitorage a long-terme de structures existantes ou de nouvelles structures pendant leur durée de service. Us sont peu encombrants, nécessitent moins de câblage et sont capables de mesurer des valeurs absolues, un attribut essentiel pour Ie monitorage a long terme. De plus, ils peuvent être associés à des méthodes d'évaluation non-destructive pour mieux connaitre l'état de santé des structures. La recherche actuelle a démontré Ie potentiel des PRF et des CFO dans Ie domaine de génie civil. L'utilisation des PRF comme renforcements externes est devenue une technique très efficace pour augmenter la résistance des structures en béton armé. Toutefois, peu d'études ont porte sur la durabilité à long terme des matériaux composites utilisés pour Ie renforcement externe des poutres en bêton arme. Par conséquent, quelques incertitudes restent quant a leur résistance à la fatigue, combinée avec des conditions extrêmes comme Ie climat nordique. Les CFO ont été intégrés avec succès dans des PRF et testes sous des conditions de charge différentes. Peu d'études portent sur leur résistance a un chargement cyclique, et aucune étude n'a encore été publiée sur leur durabilité à l'exposition environnementale. II est important de comprendre leur comportement dans ces conditions avant de les intégrés à large échelle dans des projets de monitorage.Abstract: In Canada, the extent of deterioration has prompted many authorities, including the federal and provincial governments, to investigate the potential use of fibre-reinforced polymer (FRP) products to extend the life of their existing structures. Fibre optic sensors (FOS) are serious candidates for the long-term monitoring of both existing and new structures throughout their working life. Research up to date demonstrated the potential of both FRP and FOS systems in the civil engineering field. The FRP systems used as an external reinforcement proved to be very efficient in increasing the strength of concrete structures. However, few studies focused on the long-term durability of these materials when used as external reinforcement of RC beams. As a result, there is a concern regarding the fatigue resistance of these materials when they are exposed to harsh environmental conditions. Previous studies showed that the FOS systems were successfully integrated in FRP products and tested in various loading conditions. A few studies touch upon the fatigue resistance of FOS, and no study has been reported on their durability when exposed to aggressive environments. It is important to understand the behaviour of FOS when they are submitted to these conditions before implementing them extensively in long-term health monitoring projects. This extensive experimental project was undertaken in order to assess the durability of FOS systems installed on the FRP used as external reinforcement for reinforced concrete beams. Knowing that the FOS installed on a support structure was submitted to various loading and water exposure conditions, the durability of both the FOS and RC beams strengthened with carbon-fibre-reinforced polymers was assessed. The originality of this study consists in the fact that, to the author's knowledge, it is the only experimental program on the durability of FOS installed on a structural element submitted to various fatigue and post-fatigue loading conditions. In addition, it combines the effects of fatigue loading with water exposure conditions. The maximum strain values as well as the numbers of fatigue cycles to which the FOS were tested are larger than in any other previous study. Moreover, the RC beams strengthened with FRP tested in the same conditions with the FOS, were submitted to environmental fatigue, that is water exposures combined with fatigue loading. Finally, the impact resonance method (IRM), a non-destructive testing technique, was for the first time employed to monitor fatigue damage for this type of specimens."--Résumé abrégé par UMI

Advanced Sensing, Fault Diagnostics, and Structural Health Management

Advanced sensing, fault diagnosis, and structural health management are important parts of the maintenance strategy of modern industries. With the advancement of science and technology, modern structural and mechanical systems are becoming more and more complex. Due to the continuous nature of operation and utilization, modern systems are heavily susceptible to faults. Hence, the operational reliability and safety of the systems can be greatly enhanced by using the multifaced strategy of designing novel sensing technologies and advanced intelligent algorithms and constructing modern data acquisition systems and structural health monitoring techniques. As a result, this research domain has been receiving a significant amount of attention from researchers in recent years. Furthermore, the research findings have been successfully applied in a wide range of fields such as aerospace, manufacturing, transportation and processes

International Conference on Civil Infrastructure and Construction (CIC 2020)

This is the proceedings of the CIC 2020 Conference, which was held under the patronage of His Excellency Sheikh Khalid bin Khalifa bin Abdulaziz Al Thani in Doha, Qatar from 2 to 5 February 2020. The goal of the conference was to provide a platform to discuss next-generation infrastructure and its construction among key players such as researchers, industry professionals and leaders, local government agencies, clients, construction contractors and policymakers. The conference gathered industry and academia to disseminate their research and field experiences in multiple areas of civil engineering. It was also a unique opportunity for companies and organizations to show the most recent advances in the field of civil infrastructure and construction. The conference covered a wide range of timely topics that address the needs of the construction industry all over the world and particularly in Qatar. All papers were peer reviewed by experts in their field and edited for publication. The conference accepted a total number of 127 papers submitted by authors from five different continents under the following four themes: Theme 1: Construction Management and Process Theme 2: Materials and Transportation Engineering Theme 3: Geotechnical, Environmental, and Geo-environmental Engineering Theme 4: Sustainability, Renovation, and Monitoring of Civil InfrastructureThe list of the Sponsors are listed at page 1