Résumé : La technologie des armatures en matériaux composites de polymères renforcés de fibre (PRF) reste relativement récente (moins de 20 ans) et souffre d’une moins bonne réputation en termes de durabilité, ce qui tend à freiner son acceptation par les professionnels du secteur. Les travaux présentés dans ce mémoire ont pour but d’étudier les effets de l’humidité et de l’alcalinité sur les performances mécaniques et thermomécaniques de barres d’armature en PRF. Si de nos jours l’évolution des propriétés des armatures de PRF a été largement étudiée par différents chercheurs, nous n’avons que peu d’informations sur les modes de dégradation qui entrainent ces pertes de performances. Le but des travaux entrepris dans ce mémoire est de trouver des pistes d’investigation pour la compréhension de ces mécanismes de dégradation qui pourraient éventuellement par la suite être reprises dans le cadre de travaux de thèse. Les travaux qui ont été entrepris s’articulent autour de deux projets. Le premier s’intéresse à l’étude du vieillissement accéléré de barres de polymère renforcé de fibres de verre (PRFV) de différents diamètres et soumis à un environnement humide. Le second s’intéresse à l’étude de barres de PRFV et de polymère renforcé de fibres de basalte (PRFB) de même diamètre soumis à un environnement alcalin qui simule le milieu interstitiel du béton. / Abstract : The FRP rebars technology remains relatively recent and suffers from a bad reputation in terms of durability which slows its acceptation among the professionals of the construction field. The aim of the work presented in this essay is to study the effects of moisture and alkalinity on the mechanical and thermo mechanical performances of FRP rebars. Nowadays, the progressions of FRP performances have been widely studied by different researchers but we still have few knowledge about the modes of degradation which lead to performance losses. The final goal of this work is to find investigation trails for the understanding of those degradation mechanisms which could possibly be taken over as part of a thesis work. The work is divided into two projects. The first one is the study of accelerated aging of glass fibers reinforced polymer (GFRP) rebars, of different diameters, conditioned in a moist environment. The second one concerns the behavior of GFRP and basalt fibers reinforced polymer (BFRP) rebars, of same diameter, conditioned in an alkaline environment which simulates the interstitial solution of concrete.

Au cours des dernières années, la détérioration des structures en béton armé a pris une ampleur sans précédent, et ce, malgré le fait que leur durée de vie en service initialement prévue est loin d'être atteinte. La corrosion de l'armature d'acier est un des principaux facteurs réduisant la durée de vie des ponts en béton armé d'acier. Par ailleurs, l'armature en matériaux composites de polymères renforcés de fibres (PRF) constitue une solution à l'armature métallique afin de pallier au problème de la corrosion d'acier et à la détérioration des structures en béton armé. Aussi, les barres d'armature en matériaux composites de PRF possèdent une résistance en traction élevée (environ 2 à 6 fois la limite élastique de l'acier d'armature conventionnel), ce qui leur permet de constituer un renforcement structural attrayant pour les structures en béton. Le comportement d'éléments structuraux en béton armé de barres en PRF est différent de ceux en béton armé de barres d'acier. En effet, les barres en PRF possèdent un module d'élasticité relativement plus faible que celui de l'acier et ont des propriétés d'adhérence différentes de celles des barres d'acier. L'utilisation des barres d'armature en PRF pour armer les dalles de tabliers de ponts se concrétise de plus en plus avec l'avancement des recherches dans ce domaine. La recherche entamée dans le cadre de cette thèse s'inscrit dans un programme de travaux réalisés au sein de la Chaire de recherche CRSNG/Industrie sur les Matériaux composites novateurs en PRF pour les infrastructures au département de génie civil à l'Université de Sherbrooke. Le comportement de membrures en béton armé de PRF soumis à des sollicitations mécaniques constitue un des principaux axes de recherche. Dans le cadre de cette thèse, une série d'essais a été effectuée sur huit dalles de ponts à confinement interne à grande échelle. Les paramètres des essais comprennent: (1) l'épaisseur de la dalle, (2) le type et le taux d'armature transversale de l'assemblage inférieur, (3) la résistance en compression du béton, et (4) le taux d'armature dans les autres directions (armatures transversale et longitudinale de l'assemblage supérieur et l'armature longitudinale de l'assemblage inférieur). Lors des essais de chargement, les dalles ont été supportées par deux poutrelles métalliques espacées de 2000 mm centre à centre et soumises à une charge statique concentrée sur une aire de contact de 600 mm x 250 mm afin de simuler une charge de camion (87,5 kN-CL-625) et ce conformément au code Canadien sur le calcul des ponts routiers [CAN/CSA-S6-06]. Aussi, une analyse numérique du comportement des dalles testées sous charges est faite à l'aide d'un logiciel d'éléments finis ADINA version 8.2. Les essais ont montré que toutes les dalles testées ont rompu par poinçonnement, peu importe le paramètre étudié. Aussi, une épaisseur de dalle de 175 mm répond aux exigences du Canadien sur le calcul des ponts routiers [CAN/CSA-S6-06]. Par ailleurs, les résultats ont montré que la résistance en compression du béton est un paramètre qui influe sur la déflexion, les déformations dans les barres et l'ouverture de fissures. Enfin, les résultats des analyses numériques effectuées corroborent avec ceux obtenus expérimentalement.

Résumé : L’utilisation des barres en matériaux composites de polymère renforcé de fibres (PRF) comme armatures principales dans les structures en béton est devenue un axe d’intérêt pour les constructeurs des ouvrages vue de leurs caractéristiques mécaniques importantes et leur résistance chimique élevée, particulièrement, la résistance à la corrosion. L’utilisation des barres en PRF se trouve ainsi comme une solution efficace aux problèmes de durabilité des structures en béton armé traditionnelles. Néanmoins, le comportement thermique est le principal inconvénient de ces barres, dû à la différence importante entre le coefficient d'expansion thermique transversal des barres de PRF et celui du béton durci. Cette différence, entre les propriétés thermiques de ces deux matériaux, provoque une pression radiale à l’interface Barre/Béton. Cette pression engendre des contraintes thermiques circonférentielles de traction dans le béton enrobant la barre en PRF sous une augmentation de température. Lorsque ces contraintes atteignent la résistance à la traction du béton (ft), des fissures radiales se produisent causant une perte d’adhérence entre la barre et l’enrobage de béton et, éventuellement, la rupture du béton d’enrobage si le confinement du béton n'est pas suffisant. Plusieurs études expérimentales et analytiques ont été faites pour caractériser les propriétés et le comportement des éléments en béton armé de barres en PRF sous l'effet indépendant de la charge thermique et mécanique. Tandis que, pas autant de recherches n’ont été effectuées en tenant compte des charges de service réelles des structures, telles que les charges mécaniques appliquées simultanément avec une variation thermique de -30°C à + 60 °C. Cette température représente généralement la variation climatique de la température sur la terre. L’objectif de ce projet est de réaliser une étude expérimentale et analytique afin d’étudier le comportement thermique et flexionnel des dalles en béton armé de barres en PRF sous les effets combinés des charges thermique et mécanique. La charge mécanique appliquée représente 20% de la résistance ultime flexionnelle des dalles. La température a été variée de -30°C à + 60 °C, de plus, 30 cycles gel/dégel ont été appliquées. A la fin des cycles thermiques toutes les dalles ont été soumises à l’essai de flexion en quatre points jusqu’à la rupture des dalles. L’étude analytique consiste à établir un modèle analytique permettant de calculer les déformations thermiques transversales à l’interface Barre/Béton. Le modèle proposé donne des valeurs de déformations en bon accord avec les résultats expérimentaux. Les résultats de cette étude nous permettent de conclure que l’utilisation des barres de PRFV comme armatures principales des dalles en béton pour les structures implantées dans les régions caractérisées par des conditions climatiques rudes n’influe pas sur la serviabilité de ces structures. // Abstract : The use of composite material of fiber reinforced polymer (FRP) bars as main reinforcement of concrete became an attractive solution idea for buildings constructors, due to its highmechanical performance, and its high chemical resistance, particularly, corrosion resistance. This make the FRP bars an alternative solution of durability problems of traditional reinforced concrete structures. However, the thermal behaviour is the main drawback of the FRP bars, due to the important difference between the transverse coefficient of thermal expansion of FRP bars and that of the hardened concrete. This difference involves a radial pressure generated at the FRP bar/concrete interface. This pressure produces a tensile circumferential thermal stresses within a concrete cover. When these stresses reach a concrete tensile strength (fct) a radial cracks occur producing the loss of the bond between GFRP bar and the surrounding concrete, and eventually, failure of the concrete cover if the confining action of concrete is not sufficient. Several experimental and analytical investigations have been carried out to characterize the properties and behavior of FRP materials under the independent effect of thermal and mechanical loads. However, no studies was carried out to investigate the effect of the actual service conditions, as the application of a sustained load combined with a temperature varied from -30°C to +60°C which represents, generally, a temperature variation in the globe. The aim of this project is to establish an experimental and analytical study to investigate the thermal and flexural behaviour of FRP bars-reinforced concrete slabs under combined thermal and mechanical loads. The mechanical applied load represents 20% of the flexural ultimate load of slabs. The temperature was varied from -30 to +60 °C, and 30 freeze/thaw cycles. At the end of thermal cycles, all slabs were subjected to four-points bending test up to failure of slabs. The analytical study consist to establish an analytical model allow to evaluate the transverse thermal strains at the interface bar/concrete. The proposed model is in good correlation with experimental results. From this study it can be conclude that the use of GFRP bars as a principal reinforcement for concrete slabs subjected to harsh environmental conditions has no big influence on the flexural behaviour of these slabs.

The original study design called for twenty patients. Fourteen patients with 13 implants have thus far been recruited for a prospective proof of principle study to assess the effect of addition of Platelet Rich Fibrin (PRF) on interproximal papillary height (I.P.H.) at the restorative line angles when used during the second stage uncovering procedure for dental implants. The secondary objective of this study was to assess the effect on the height of the direct interproximal tissue thickness (I.T.T.) at 6 weeks following uncovering. Implants placed 3 or more months prior at Boston University School of Dental Medicine Periodontics Department were scheduled to be uncovered by the principal investigator. Second stage uncovering was performed with a conventional mid-crestal incision to place standard healing abutments. PRF membrane(s) were inserted around the implants before flap closure in an attempt to augment or thicken the interproximal papillary area. The I.P.H. was measured at the four line angles of each abutment at the highest aspect of the interproximal tissue immediately following the uncovering procedure and at 2, 4 & 6 week intervals. I.T.T. was also measured prior to surgical exposure and at 6 weeks following the uncovering procedure. Results: The use of PRF membranes around dental implants did not significantly improve I.P.H. However, a positive correlation was observed between the use of P.R.F and I.T.T. Further studies are warranted to assess the effect of PRF on the peri-implant papillary tissue.

<p>A helicopter based system equipped with a millimetre-wave fire control radar is studied for improvement of the detection probability for moving ground targets. The system is a pulse doppler radar that sends out the electromagnetic wave in repetitive pulses. The frequency in which radar sends this pulse is called Pulse Repetition Frequency (PRF). </p><p>The velocity of the moving targets is measured by spectral analysis of the pulses received. With this sort of system some targets will not be possible to detect. These targets are said to be blind for the radar. Also the measured targets can be ambiguous. A solution to this is to shift PRF during the time the radar emits itspulses on the target. This method is called PRF block staggering. The antenna is mounted on a mechanical sweep on top of the rotor of the helicopter. Because of this the time on target is limited. This means that the measured velocity resolution of the radar is also limited. </p><p>With the studied method it is possible to resolve range and velocity ambiguities. This is under the condition that it is acceptable with a reduction in the velocity resolution by a factor equal to the number of PRF blocks used. </p><p>The work leading to this thesis included developing a program in Mathworks Matlab for studying different configurations of PRFs and the effect on the detection probability.</p>

A helicopter based system equipped with a millimetre-wave fire control radar is studied for improvement of the detection probability for moving ground targets. The system is a pulse doppler radar that sends out the electromagnetic wave in repetitive pulses. The frequency in which radar sends this pulse is called Pulse Repetition Frequency (PRF). The velocity of the moving targets is measured by spectral analysis of the pulses received. With this sort of system some targets will not be possible to detect. These targets are said to be blind for the radar. Also the measured targets can be ambiguous. A solution to this is to shift PRF during the time the radar emits itspulses on the target. This method is called PRF block staggering. The antenna is mounted on a mechanical sweep on top of the rotor of the helicopter. Because of this the time on target is limited. This means that the measured velocity resolution of the radar is also limited. With the studied method it is possible to resolve range and velocity ambiguities. This is under the condition that it is acceptable with a reduction in the velocity resolution by a factor equal to the number of PRF blocks used. The work leading to this thesis included developing a program in Mathworks Matlab for studying different configurations of PRFs and the effect on the detection probability.

Range and Doppler measurement of targets for medium PRF radars is handicapped by folding and blind regions. This requires use of multiple PRFs and a resolver algorithm. The aim of the thesis is to develop various algorithms for the task and estimate their performance. Four different range and Doppler resolver algorithms and a test software is developed by using Matlab &reg / GUI and their performances due to the selected radar parameters in a multi- target environment are examined.

This dissertation shows the performance of adaptive waveforms when applied to two radar applications. One application is automatic target recognition (ATR) and the other application is range-Doppler ambiguity mitigation. The adaptive waveforms are implemented via a feedback loop from receiver to transmitter, such that previous radar measurements affect how the adaptive waveforms proceed. For the ATR application, adaptive transmitter can change the waveform's temporal structure to improve target recognition performance. For range-Doppler ambiguity mitigation application, adaptive transmitter can change the pulse repetition frequency (PRF) to mitigate range and Doppler ambiguity. In the ATR application, commercial electromagnetic software is used to create high-fidelity aircraft target signatures. Realistic waveform constraints are applied to show radar performance. The radar equation is incorporated into the waveform design technique and template-based classification is performed. Translation invariant feature is used for inaccurately known range scenario. The performance of adaptive waveforms is evaluated with not only a monostatic radar, but also widely separated MIMO radar. In MIMO radar, multiple transmit waveforms are used, but spectral leakage caused by constant-modulus constraint shows minimal interference effect. In the range-Doppler ambiguity mitigation application, particle-filter-based track-before-detect for a single target is extended to track and detect multiple low signal-to-noise ratio (SNR) targets, simultaneously. To mitigate ambiguity, multiple PRFs are used and improved PRF selection technique is implemented via predicted entropy computation when both blind and clutter zones are considered.

The advantages of fiber-reinforced polymer (FRP) composite material have attracted structural and architectural engineers as alternative construction materials of the traditional wood, steel and concrete. Concrete-filled FRP tubes (CFFTs) system is one of the most promising applications of the FRP composit material. This innovative integrated system can protect RC structures from aggressive environmental conditions; sequentially expand the service life of structures. Nevertheless, limited knowledge is available on the CFFT system at extreme service environments. Data related to durability of the CFFT as integrated system comparing with conventional ones is one of the major challenges that need to be addressed. These data are moer required prior to the widespread acceptance and implementation of FRP materials in civil infrastructure. Farther, comprehensive databases in this specific are critical to provide designers and practicing engineers with the knowledge to select the best solution toward achieving a sustainable built environment. This thesis focuses on evaluating the short and long term effect of freze-thaw cycles on the mechanical behavior of the filament wound glass-FRP (GFRP) tubes. In addition, the thesis evaluating the axial performances of reinforced and unreinforced CFFT columns through experimental and theoretical study. To fulfill the objectives of this research, an experimental program has been designed to examine three main parts. (I) Mechanical properties of the GFRP tubes; (II) The axial behavior of CFFT cylinders; (III) The axial behavior of CFFT reinforced and unreinforced columns. The effect of five parameters and their interactions were investigated; namely, the effect of different freze-thaw cycles (in dry air, frsh and/or salt water), number of cycles (100 and/or 300 cycles), two different thicknesses (2.65 mm and 6.4 mm) of the GFRP tube. The influence of using different types of internal longitudinal reinforcement (steel, GFRP, and carbon FRP bars) and the type of transverse reinforcements (spiral steel or FRP tubes) are included in the test variables. Based on the finding of experimental investigation regarding mechanical properties of the GFRP tubes (part I), neither the type nor the number of freze--thaw cycles affect the strength of GFRP tube used in this study. However, increasing in the stiffness, reductions in the strains and transition in failure mechanisms are identified after 300 freze-thaw cycles. The experimental results of axial compression tests on CFFT cylinders (part II) indicated low influence of the freze-thaw cycles on the average ultimate strength of CFFT tube with the large thickness. While, significant and sever degradation was reflected on the behavior of CFFT cylinders with the small thickness after 300 freze-thaw cycles. Based on the experimental test results of (part II) environmental reduction factors were proposed to consider the effect freze/thaw cycles on the strength capacity of CFFT cylinders. Also, the regression analysis was used to predict the service life environmental reduction Factors to design CFFT member for up to 75 years. In addition, an assessment of selected FRP-confined models has been presented to predict the ultimate strength of CFFT cylinders based on the test results of (part I). Finally, comparisons between the experimental results and those predicted by the selected models were presented. The experimental investigation on the performance of reinforced CFFT columns (part III) indicated that the freze-thaw exposure brings about individual degradation, in different levels, in the component of the CFFT (GFRP tube, concrete and reinforcement) as integrated systems. This degradation resulted in reduction in the axial carrying capacities of the conditioned columns. Nevertheless, an increase in compressive strength of the CFFT columns was evident over the RC conventional columns. Based on the test results of this (part III), environmental reduction factors were proposed to account for the effect of freze/thaw cycles on the axial load capacity of reinforced and unreinforced CFFT columns. The data obtained from the test results of (part I), predicted confined compressive strength optained from (part II) and the proposed environmental reduction factors from (part III) were used in the ACI440-2R-08 and CAN/CSA S806-08 design equations to predict the nominal capacity of CFFT columns in sever environmental condition.

Deterioration of reinforced-concrete (RC) structures due to corrosion of steel limits the service-life and increases the rehabilitation costs. Concrete slabs in parking structures deteriorate faster than any other structural elements because of direct exposure to high concentrations of chlorides used for snow and ice removal-during winter seasons. The use of fiber-reinforced polymer (FRP) bars as an alternative to conventional steel has emerged as a realistic and cost-effective solution to overcome the corrosion problems, particularly for concrete structure exposed to harsh environmental conditions. Design of RC flat slabs is often compromised by their ability to resist shear stresses at the punching-shear surface area. The connections between slabs and supporting columns could be susceptible to high shear stresses and might cause brittle and sudden punching-shear failure. These connections may become the starting points leading to catastrophic punching-shear failure of a flat slab system when the steel reinforcement corrodes. Extensive research work has been conducted on the punching-shear behaviour of steel-reinforced flat slabs. The punching-shear strength of RC flat slabs reinforced with glass fiber-reinforced polymer (GFRP) bars, however, is yet to be fully investigated and understood. This is due to the limited research work on the subject and to the numerous parameters affecting punching-shear behaviour. In addition, the current FRP design codes and guidelines do not provide rational design models addressing the contribution of the FRP as shear reinforcement (stirrups) for FRP-RC flat slabs. Thus, this study aims at investigating the punching-shear behaviour of concrete two-way slabs reinforced in flexure with GFRP bars. The investigation included two-way test specimens without shear reinforcement and others with carbon or glass FRP stirrups to evaluate the performance of specimens without shear reinforcement and the effect of shear reinforcement on the punching-capacity and performance. To achieve this, experimental and analytical studies were conducted. The experimental program included twenty-six interior slab-column connections reinforced with GFRP bars and two specimens reinforced with steel bars for comparisons. The specimens were tested through two phases. Phase I, focused on the two-way slabs without shear reinforcement and the investigated parameters were: (i) flexural reinforcement ratio (ranged from 0.34% to 1.66%) and type (steel and GFRP); (ii) GFRP compression reinforcement; (iii) slab thickness (200 mm and 350 mm); (v) column dimensions (300 × 300 mm and 450 × 450 mm); (iv) concrete strength (normal and high-strength concretes). Phase II, focused on the use of FRP shear reinforcement (stirrups) and its effectiveness and contribution to the punching-shear capacity. The test variables considered in Phase II were: (i) the material of stirrups (carbon and glass FRP); (ii) shear reinforcement ratio; (iii) stirrup spacing; (iv) the effect of flexural reinforcement ratio on the effectiveness of the shear reinforcement. The effect of the different parameters considered in the two phases of the experimental work were presented and discussed in four journal papers. Moreover, the test results and the findings contributed to the first field implementation of GFRP bars in two flat slabs parking garages in Québec's city, which were Québec's city hall (Québec, Canada, 2010) and La Chancelière parking garage (the world's first flat-slab parking garage totally reinforced with GFRP bars) (Québec, Canada, 2011). On the other hand, the analytical study included assessing the accuracy of the current punching-shear design provisions through comparing the test results of the specimens tested herein and 35 specimens from literature. The provisions included CSA 8806-12 (2012), ACI 440 (2006), BS 8110 (1997), and JSCE (1997).