Comportement en flexion de poutres tubulaires rectangulaires (en polymère renforcé de fibres) en béton armé et post-contraintes : études expérimentale et analytique

Abstract : Corrosion damage is recognized as a crucial factor for existing concrete bridge girders and corresponding consequences are significant. A promising solution has recently been proposed using posttensioned (PT) concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) to effectively improve the performance of new concrete structures. Despite this system demonstrated benefits in terms of improving structural behavior, there still is a lack of research, including the functional reliability of posttensioned rectangular CFFT members. Moreover, there are no code provisions for the flexural design of PT rectangular CFFT members. To achieve their broad-based implementation in civil infrastructures, understanding of their flexural behavior is essential. This study presents the results of a comprehensive test program that was aimed at investigating the flexural behavior of rectangular CFFT beams posttensioned with unbonded steel tendons to address the knowledge research gaps in this field. The tests intend to simulate a number of design parameters, which are mainly governed by flexural loading. Fifteen full-size beams with internal steel bars were tested, including thirteen PT CFFTs and two PT concrete beams along with one non-PT CFFT from the literature for comparison. The investigated parameters are i) GFRP tube thickness ranged from 6.0 mm to 12.3 mm; ii) Tube fiber structural laminate; iii) Tube confinement versus steel stirrups; iv) Number of prestressing tendons and level of prestressing; v) Concrete compressive strength [(normal and high strength concrete (NSC and HSC)]; vi) Total reinforcement index; vii) Attaching a thin Carbon FRP-laminated embedded in tension flange and its ratio; and viii) Loading scheme (static and cyclic). Moreover, an analytical study was conducted to develop a model to predict the ultimate strength of prestressed CFFT members. The model is based on strain compatibility and force equilibrium, which account for the material constitutive relationships for FRP tube laminates, steel strands, and non-linearity of concrete. The accuracy of the proposed model is also verified against the experimental results. Finally, a new design equation, as an extension to AASHTO (2012) equation, is also established based on a regression analysis of the test results to predict the ultimate flexural capacity of the tested beams, which significantly impacts the design practice of such members. The experimental results demonstrated the feasibility and construction of rectangular CFFTs posttensioned with steel tendons. The test results indicated that rectangular CFFT beams prestressed with unbonded steel strands could effectively replace conventional members made from traditional materials or identical rectangular CFFT without prestressing, in terms of similar or better structural performance. The flexural behavior of the tested PT CFFT beams is highly depended on the FRP tube confinement, laminate, thickness, and attaching a thin Carbon FRP-laminated embedded in tension flange, and to a much less extent, on the magnitude of the prestress level, the number of strands, concrete strength, and loading scheme. Furthermore, it was found that neglecting concrete confinement in the proposed model highly underestimates the flexural strength. The promising results of this study can provide the impetus for constructing a new sustainable and high-performance hybrid structural rectangular PT CFFT elements.Les dommages des infrastructures en béton dus à la corrosion représentent un facteur crucial pour les poutres de pont en béton et les conséquences associées à ces dommages sont très importantes. Malgré les avantages évidents de ce système en termes d'amélioration du comportement structural et de durabilité, il y a encore un grand manque de données expérimentales et de modélisation, y compris la faisabilité fonctionnelle des éléments tubes en polymère renforcé de fibres (PRF) et remplis de béton (TPRB) rectangulaires PC. De plus, il n'y a pas de normes pour la conception en flexion de ces éléments. Pour parvenir à la mise à l’échelle et à l’introduction de ces éléments TPRB dans les infrastructures civiles, la compréhension et la modélisation de leur comportement en flexion est indispensable. Étant la toute première étude expérimentale sur le sujet, cette étude présente les résultats d'un programme expérimental visant à étudier le comportement en flexion des poutres TPRB rectangulaires PC (avec des tendons en acier post-tensionnés) pour combler la lacune de recherche susmentionnée. Le programme expérimental vise à simuler un certain nombre de paramètres de conception des TPRB-PC. Treize poutres (à échelle réelle, incorporant des barres d’armature en acier) dont douze TPRB rectangulaires PC, deux poutres en béton armé conventionnel et PC et une poutre TPRB sans post-tension (pour comparaison) ont été testées. Les principaux paramètres étudiés sont : (i) l'épaisseur du tube GFRP variant de 6,0 mm à 12,3 mm; (ii) l’orientation et l’empilement des couches des fibres dans les tubes ; (iii) le confinement par des tubes par rapport aux étriers en acier dans les poutres conventionnelles; (iv) le nombre de tendons et le niveau de précontrainte ; (v) la résistance à la compression du béton [béton normal (BO) et béton à haute résistance (BHP)] ; (vi) l'indice de renforcement total; (vii) l’effet de l’intégration d’une fine lamelle de carbone en PRF dans une la zone tendue du tube en PRF; et (viii) type de chargement (statique et cyclique). De plus, une étude analytique a été menée afin de développer un modèle permettant de prédire la force ultime des éléments TPRB-PC. Le modèle est basé sur la compatibilité des contraintes et l'équilibre des forces, qui tiennent compte des relations constitutives des matériaux (laminés de tubes FRP, tondons d'acier, et la non-linéarité du béton). La précision du modèle proposé est également vérifiée par rapport aux résultats expérimentaux. Enfin, une nouvelle équation de conception, en tant qu'extension de l'équation de l'AASHTO (2012), est également établie (sur la base d'une analyse de régression des résultats expérimentaux) pour prédire la capacité de flexion ultime des poutres TPRB-PC testées, ce qui pourra avoir un impact significatif sur la pratique de conception des éléments TPRB-PC. Les résultats expérimentaux ont démontré la faisabilité des éléments TPRB PC avec des tendons d'acier. Les résultats ont ainsi indiqué que les poutres TPRB PC peuvent effectivement remplacer les éléments conventionnels fabriqués à partir de matériaux traditionnels ainsi que les TPRB sans pré ou post-tension, tout en démontrant des performances structurales nettement supérieures. Le comportement en flexion des poutres TPRB -PC testées dépend fortement du confinement des tubes en PRF, de la séquence d’enroulement et de l’orientation des fibres, de l'épaisseur et de l’intégration d'une mince couche de laminé en PRF de carbone et, dans une moindre mesure, de l'ampleur du niveau de post-tension, du nombre de torons, de la résistance du béton et du type de chargement. En outre, il a été constaté que le fait de négliger l’effet de confinement du béton dans le modèle proposé sous-estime fortement la résistance en flexion. Les résultats prometteurs de cette étude peuvent promouvoir la construction des structures hybrides (faites à partie des TPRB rectangulaires PC) plus durables et plus performantes

Challenges facing women living with HIV in Upper Egypt

This research aims to identify challenges that face women living with HIV in Upper Egypt in order to help policy makers and different stakeholders to overcome those challenges. Interviews with women living with HIV from different governorates in Upper Egypt were conducted. In addition, this research included interviews with national AIDS program officials and NGOs managers to obtain different perspectives about the condition of women living with HIV. Women represent half of people living with HIV around the world. The burden of disease on women is even more challenging in many countries due to gender inequality. The effect of culture in Upper Egypt on women living with HIV was an added value to this research as there is shortage in researches that tackled this problem in this particular area in Egypt. Despite efforts to fight HIV in Egypt and to reduce stigma and discrimination, women living with HIV in Upper Egypt face many challenges. What are those challenges and how can Egypt overcome them? Main findings included that women living with HIV in Upper Egypt need a stigma free reproductive health services. They need to disclose about their illness without fear of stigma. Women face many difficulties to access reproductive health services upon disclosure about their status. Women might transfer the virus to their children due to mismanagement of their cases or lack of proper services in health care provision during child birth. Moreover, there is a shortage in the services provided for PLHIV in Upper Egypt including medications’ distributing centers and laboratory tests. Finally, there is a pressing social stigma against PLHIV which results in low utilization of testing services

Comparison of Sumudu and Laplace decomposition method for solving fractional Lane-Emden type differential equations

In this work we discuss the solution of delay differential equations of  the fractional order of Lane-Emden type equation using Sumudu and Laplace transforms with decomposition method , definitions and some useful theorems are stated

Fc-Engineered Therapeutic Antibodies: Recent Advances and Future Directions.

Monoclonal therapeutic antibodies have revolutionized the treatment of cancer and other diseases. Fc engineering aims to enhance the effector functions or half-life of therapeutic antibodies by modifying their Fc regions. Recent advances in the Fc engineering of modern therapeutic antibodies can be considered the next generation of antibody therapy. Various strategies are employed, including altering glycosylation patterns via glycoengineering and introducing mutations to the Fc region, thereby enhancing Fc receptor or complement interactions. Further, Fc engineering strategies enable the generation of bispecific IgG-based heterodimeric antibodies. As Fc engineering techniques continue to evolve, an expanding portfolio of Fc-engineered antibodies is advancing through clinical development, with several already approved for medical use. Despite the plethora of Fc-based mutations that have been analyzed in in vitro and in vivo models, we focus here in this review on the relevant Fc engineering strategies of approved therapeutic antibodies to finetune effector functions, to modify half-life and to stabilize asymmetric bispecific IgGs

Effect of particle morphology on film cracking

233 p.With the aim of reducing VOC emissions and producing more sustainable coatings and adhesives, solvent borne polymers are gradually being replaced by water-based alternatives. However, the mechanical properties of water borne systems are typically not as good as those of solvent borne products due to differences in the film formation process.The thesis aimed at shedding some light on film formation and cracking problem to be able to design soft core-hard “shell” latexes that yield VOC and crack free, mechanically strong coatings that can be cast at low temperatures. These are particles consisting of a soft core covered by patches of hard polymer. Different strategies have been used to overcome the film formation and cracking problem like . A mathematical model for cracking prediction and stress calculation during drying of aqueous dispersions of soft core-hard “shell” particles was developed. The model solved numerically the incompressible Navier-Stokes and continuity equations using COMSOL Multiphysics. The model was validated with experimental data. A good agreement between experimental results and model predictions was achieved.The results presented in this work highlight that careful design of soft core-hard “shell" polymer dispersions allows overcoming the film formation dilemma frequently found in water borne coatingsIndustrial Liaison Program in Polymerization in Dispersed Media POLYMAT

STR-937: BEHAVIOUR OF FRP-REINFORCED CFFT COLUMNS UNDER AXIAL COMPRESSION LOADING

This paper presents the test results of an experimental study aimed at investigating the axial behaviour of CFFT columns internally reinforced with steel and FRP bars. A total of eight reinforced concrete (RC) and concrete-filled FRP tube (CFFT) columns were constructed and tested until failure. All columns had 1900-mm in height and 213-mm in diameter. The test parameters were: (1) internal reinforcement type (steel, glass FRP (GFRP), or carbon FRP (CFRP) bars) and amount, (2) GFRP tube thicknesses, and (3) nature of axial loading type (i.e. monotonic and cyclic). The experimental results revealed that the CFFT columns reinforced with GFRP bars exhibited similar responses compared to their counterparts reinforced with steel bars with no significant difference in terms of ultimate axial strength and strain capacities. Providing the GFRP tubes of the CFFT columns significantly enhanced the strength and strain capacities and attributed to change the mode of failure from axially dominated material failure (for the control columns) to instability failure (for the CFFT columns). Furthermore, the envelop curve of the CFFT reinforced column tested under axial cyclic loading is almost identical to the axial stress-strain curve of the same specimen tested under axial monotonic loading. However, the ultimate axial and hoop rupture strain was slightly larger for the specimen subjected to axial cyclic loading. Finally, using FRP bars instead of conventional steel bars in the CFFT columns can provide a step forward to develop a promising totally corrosion-free new structural system

On some generalizations of certain retarded nonlinear integral inequalities with iterated integrals and an application in retarded differential equation

AbstractIn this paper, we investigate some new nonlinear retarded integral inequalities of Gronwall–Bellman–Pachpatte type. These inequalities generalize some former famous inequalities and can be used as handy tools to study the qualitative as well as the quantitative properties of solutions of some nonlinear retarded differential and integral equations. An application is also presented to illustrate the usefulness of some of our results in estimation of solution of certain retarded nonlinear differential equations with the initial conditions

Forces Driving the Development of Particle Morphology of Waterborne Polymer Dispersions

[EN] Particle morphology is a key characteristic of the waterborne polymer dispersions and plenty of effort has been dedicated to understand the mechanisms controlling the development of the morphology during polymerization. The availability of new characterization techniques that provide unprecedented quantitative details of the particle morphology have questioned the ideas about the driving forces ruling the development of the morphology. In this article, the case is considered of a seeded emulsion polymerization in which the second stage polymer (Polymer 2) is more hydrophobic than the seed polymer and a water-soluble initiator is used. Simulations of the effect of the different forces involved in the formation of the particle morphology carried by integrating the Navier-Stokes are compared with available experimental results. If is found that the interfacial tensions are responsible for the penetration of clusters of polymer 2 within the seed polymer and the spread of these clusters over the surface of the particle. On the other hand, van der Waals forces control coalescence of the clusters both at the surface and in the interior of the particle.The support of the partners of the Industrial Liaison Program on Polymerization in Disperse Media (Allnex, Akzo-Nobel, Arkema, Asian Paints, BASF, DSM, Elix Polymers, Inovyn, 3M, Stahl, Synthomer, Vinavil, Wacker) is acknowledged

Comportement axial de colonnes en béton armé renforcées de tubes en matériaux composites

Abstract : The construction industry is expressing great demand for innovative and durable structural members such as bridge decks and piers, piling, and poles. Many steel-reinforced concrete structures subjected to de-icing salts and marine environments require extensive and expensive maintenance. Fiber-reinforced polymers (FRPs) have recently gained wide acceptance as a viable construction material for repair, rehabilitation, or new construction of the aging infrastructures particularly those exposed to harsh environment conditions. The promising concept of concrete-filled FRP tube (CFFT) system, that may be further reinforced with steel or FRP bars, has raised great interest amongst researchers in the last decade. The CFFT technique has been used successfully in different concrete structure elements such as pier column and girder for bridges and also as fender piles in marine structures. The FRP tube acts as a stay-in-place structural formwork, a noncorrosive reinforcement for the concrete for flexure and shear, provides confinement to the concrete in compression, and the contained concrete is protected from intrusion of moisture with corrosive agents that could otherwise deteriorate the concrete core. Using FRP bars instead of conventional steel bars in the CFFT columns can provide a step forward to develop a promising totally corrosion-free new structural system. Nonetheless, the axial behaviour of FRP bars as longitudinal reinforcement in compression members has yet to be explored, especially for the CFFT columns. To date, most of the experimental investigations performed on FRP confined concrete columns have considered short, unreinforced, small-scale concrete cylinders, tested under concentric, monotonic, and axial load. The slenderness ratio, internal longitudinal reinforcement type (steel or FRP bars), and axial cyclic loading effects on the behaviour of FRP confined concrete long columns, however, have received only limited research attention. To address such knowledge gaps, this study aimed at investigating the behaviour of the CFFT long columns internally reinforced with steel or FRP bars tested under monotonic and cyclic axial loading. A total of ten reinforced concrete (RC) and CFFT columns were constructed and tested until failure. All columns had 1900-mm in height and 213-mm in diameter. The investigated parameters were: i) the effect of internal reinforcement type (steel, glass FRP (GFRP), or carbon FRP (CFRP)) and amount, ii) GFRP tube thicknesses, and iii) nature of loading (i.e. monotonic and cyclic). The effect of the different parameters on the axial behaviour of the tested columns is presented and discussed. The research work presented in this dissertation has resulted in one paper submitted to the Elsevier Journal of Engineering Structures (manuscript ID: ENGSTRUCT-D-15-01381) and one accepted conference paper submitted to the 5 th International Structural Specialty Conference (CSCE 2016), London, Ontario, June 1st - 4th, 2016. The experimental test results showed that the CFFT columns reinforced with GFRP bars exhibited similar responses compared to their counterparts reinforced with steel bars with no significant difference in terms of ultimate axial strength and strain capacities. The GFRP tubes provided significant confinement of the tested specimens attributing to shift the mode of failure from axially dominated material failure to flexural-dominated instability failure. The results also indicated that the plastic strains of the FRP-reinforced CFFT columns was linearly proportional to the envelop unloading strains (εun,env). The relationship depended little on level of confinement, but strongly on the longitudinal reinforcement amount and type, particularly when εun,env > 0.0035. On the other hand, an analytical investigation was conducted to examine the validity of the available design provisions for predicting the ultimate load capacity of tested columns. The results of the analysis were compared with the experimental values. It was found that the ACI 440.R1 (2015), CSA S806 (2012), and CSA S6-06 (2010) design provisions provided higher conservative results for the GFRP-reinforced control specimens than that of steel-reinforced specimen. This might be due to neglecting the contribution of the compressive resistance of the GFRP bars to the axial carrying capacity. Furthermore, for FRP-reinforced CFFT columns, the ACI 440.2R (2008), CSA S806 (2012), and CSA S6-06 (2010) provisions results over the experimental results were an average of 1.68±0.31, 1.57±0.18, and 1.72±0.35 with a COV of 18.4%, 11.3%, and 20.5%, respectively. By considering the confinement codes limits, the CSA S806 (2012) showed better correlation for the ultimate carrying capacity based on the average than the CSA S6-06 (2010) and ACI 440.2R (2008), particularly for specimens cast with tube Type B.Résumé : L'industrie de la construction exprime une grande demande pour les structures innovantes et durables tels que les tabliers de ponts et les quais, les pieux et les poteaux. Plusieurs structures en béton armé sont soumises à des sels de déglaçage et à des environnements marins qui exigent un entretien coûteux. Les polymères renforcés de fibres (PRF) ont récemment été reconnus en tant que matériau de construction viable pour la réparation, la réhabilitation ou la construction de nouvelles infrastructures vieillissantes en particulier celles exposées à des conditions d'environnement sévères. Le concept prometteur du système de tube rempli de béton PRF (CFFT), qui peut être encore renforcé avec de l'acier ou des barres en PRF, a amorcé un grand intérêt parmi les chercheurs durant la dernière décennie. La technique CFFT a été utilisée avec succès dans les différents éléments de structure en béton tels que les colonnes et les poutres de ponts et aussi comme des pieux pour les structures marines. Le tube en PRF agit comme un coffrage structural sur place, un renforcement non corrosif pour le béton en flexion et au cisaillement en utilisant l'orientation des fibres multidirectionnelle, fournit un confinement au béton en compression, et le béton est protégé de toute intrusion d'humidité des agents corrosifs qui, autrement, pourraient détériorer le noyau de béton (ACI 440. R-07 (2007)). L’utilisation des barres de PRF au lieu de barres d'acier conventionnelles dans les colonnes CFFT peut fournir un pas en avant pour développer un nouveau système structurel. Néanmoins, le comportement axial des barres en PRF comme armatures longitudinales dans les membrures en compression n'a pas encore été exploré, en particulier pour les colonnes CFFT. À ce jour, la plupart des études expérimentales effectuées sur les colonnes en béton confinés de PRF, ont considéré des cylindres en béton, courts, à petite échelle non armés, et testés sous un charge concentrique, monotone, et axiale. Le rapport d'élancement, le renfort longitudinal interne (acier ou barres en PRF), et les effets du chargement axial cyclique sur le comportement des colonnes élancées de béton confinés et en PRF, ont connu une recherche limitée. Pour combler ce manque de connaissance, cette étude vise à étudier le comportement des colonnes élancées CFFT armé en acier ou en barres de PRF testées sous charges axiales monotones et cycliques. Un total de dix colonnes en béton armé (RC) et CFFT été fabriquées et testées jusqu'à la rupture. Toutes les colonnes ont 1900 mm de hauteur et 213 mm de diamètre. Les paramètres étudiés sont les suivants: i) l'effet de type de renforcement interne et la quantité de renforcement, ii) les épaisseurs de tubes PRV, et iii) le type de chargement (monotone et cyclique). L'effet des variables considérées sur le comportement axial des colonnes testées dans le travail expérimental est présenté et discuté. Le travail de recherche présenté dans cette analyse a fait l’objet d’un article scientifique soumis à Elsevier Journal of Engineering Structures (manuscrit ID: ENGSTRUCT-D-15-01381) et un article lors d’une conférence acceptée soumis à la 5ième International Structural Specialty Conference (CSCE 2016), London, Ontario, Juin 1er - 4ième, 2016. Les résultats des essais expérimentaux ont montré que les colonnes CFFT renforcées de barres en PRFV présentaient des réponses similaires par rapport à leurs homologues renforcées avec des barres d'acier sans différence significative en termes de capacité ultime de résistance axiale et de déformation. Les tubes en PRFV fournissent un confinement significatif des échantillons testés attribuant à changer le mode de rupture, c’est-à-dire d’une rupture des matériaux axialement à une rupture d’instabilité en flexion. En outre, l'augmentation de l'épaisseur du tube en PRFV de 2,9 à 6,4 mm améliore les rapports de résistance et de déformation de 25 % et 12 %, respectivement. Les résultats indiquent également que les déformations plastiques des colonnes renforcées de PRF sont linéairement proportionnelles aux enveloppes de tension de déchargement (εde,env). La relation dépend un peu du niveau de confinement, mais fortement de la quantité et du type de renfort longitudinal, en particulier lorsque εde,env > 0,0035. D'autre part, une investigation a été menée pour examiner la validité des dispositions de conception disponibles pour prédire la capacité de la charge ultime des colonnes testées. Les résultats de l'analyse ont été comparés avec les valeurs expérimentales. Il a été constaté que les prévisions de l'ACI 440.R1 (2015), CSA S806 (2012), et CSA S6-06 (2010) ont fourni des résultats conservateurs plus élevés pour les échantillons de contrôle en PRFV que celui de l'échantillon d'acier. Cela peut être dû à la négligence de la contribution de la résistance à la compression des barres de PRFV à la capacité de charge axiale. En outre, pour les colonnes de CFFT renforcées de PRF, les prévisions de l'ACI 440.2R (2008), du CSA S806 (2012), et du CSA S6-06 (2010) étaient de 1,68 ± 0,31, 1,57 ± 0,18 et 1,72 ± 0,35 avec un COV de 18,4 %, 11,3%, et 20,5%, respectivement. En considérant les limites des codes de confinement, le code CSA S806 (2012) a révélé les meilleures prévisions pour la capacité de charge ultime basée sur la moyenne que celui du code CSA S6-06 (2010) et de l’ACI 440.2R (2008), en particulier pour les échantillons réalisés avec des tubes de Type B