Epoxy intumescent coatings are fire protection systems for steel structural elements that are widely used in applications that protection from severe hydrocarbon fires is required, such as oil and gas facilities. These polymer coatings react upon heating and expand into a thick porous char layer that insulates the protected steel element. In the typical fire scenarios for these applications, the intumescent coatings must resist very high heat fluxes and highly erosive forces from ignited pressurised gases. Hence, continuous fibre reinforcement is embedded in the thick epoxy coating during installation, so as to ensure the integrity of the weak intumesced char during fire exposure. This reinforcement is typically in the form of a bidirectional carbon and/or glass fibre mesh, thus under normal service conditions a fibre-reinforced intumescent coating (FRIC) is essentially a lightly fibre-reinforced polymer (FRP) composite material. This thesis examines the impacts of embedded high strength fibres on the tensile behaviour of epoxy intumescent materials in their unreacted state prior to fire exposure, and the potential enhancements that arise in the structural performance of elements protected with FRICs. An experimental programme is presented comprising tensile coupon tests of unreacted intumescent epoxies, reinforced with different fibre meshes at various fibre volume fractions. It is demonstrated that the tensile properties of FRICs can be enhanced considerably by including increasing amounts of carbon fibre reinforcement aligned in the principal loading direction, which can be tailored in the desired orientation on the coated structural members to enhance their load carrying capacity and/or deformability. An experimental study is presented on coated intact and artificially damaged I-beams (simulating steel losses from corrosion) tested in bending, demonstrating that FRICs can enhance the flexural response of the beams after yielding of steel, until the tensile rupture of the coatings. An analytical procedure for predicting the flexural behaviour of the coated beams is discussed and validated against the obtained test results, whereas a parametric analysis is performed based on this analytical model to assess the effect of various parameters on the strengthening efficiency of FRICs. The results of this analysis demonstrate that it is feasible to increase the flexural load capacity of thin sections considerably utilising the flexural strength gains from FRICs. Finally, a novel application is proposed in this thesis for FRICs as a potential system for structural strengthening or retrofitting reinforced concrete and concrete-encased steel columns by lateral confinement. An experimental study is presented on the axial compressive behaviour of short, plain concrete and concrete-encased structural steel columns that are wrapped in the hoop direction with FRICs. The results clearly show that epoxy intumescent coatings reinforced with a carbon fibre mesh of suitable weight can provide lateral confinement to the concrete core resisting its lateral dilation, thus resulting in considerable enhancements of the axial strength and deformability of concrete. The observed strengthening performance of the composite protective coatings is found to be at least as good as that of FRP wraps consisting of the same fibre reinforcement mesh and a conventional, non-intumescent epoxy resin. The predictive ability of existing design-oriented FRP confinement models is compared against the experimental results, and is found to be reasonably precise in predicting the peak strength of the tested columns, hence existing models appear to be suitable for design and analysis of column strengthening schemes with the proposed novel FRIC system. The research presented herein shows clearly that FRICs have a strong potential as alternative systems for consideration in the field of structural strengthening and rehabilitation, since they can provide substantial enhancements in the load carrying capacity for both applications considered. At the same time FRICs can thermally protect the underlying structural elements in the event of a fire, by intumescing and charring, thus potentially eliminating the need for additional passive fire protection that is common with conventional fire-rated FRP wrapping systems. Although this thesis provides a proof-of-concept for use of the proposed novel FRICs as structural strengthening materials, considerable additional research is particularly required to study their fire protection performance when applied to concrete substrates, to make use of the proposed hybrid functionality with confidence.

The structural adhesives widely used in structural strengthening applications are thermoset ambient cure adhesive polymers. At ambient temperatures, these polymers are in a relatively hard and inflexible state. At higher temperatures, the material becomes soft and flexible. The region where the molecular mobility changes dramatically is known as the glass transition temperature Tg and often is presented as a single value. Epoxy polymers exhibit a significant reduction in mechanical properties near glass transition temperature Tg when they are exposed to elevated temperatures. Glass transition temperature Tg is used to characterise the change in epoxy adhesive properties with changing temperature. The mechanical properties of epoxies tend to improve with curing temperature. This is because the crosslink density between the adhesive molecular structures increases during the curing process consequently the Tg improves. The aims of this work are first to demonstrate the importance of curing temperature. Second, to investigate the influence of glass transition temperature !! improvement on the performance of EB-FRP strengthened steel structures in flexure at ambient and elevated temperatures. Third, to compare analytical results with experimental results from the flexure tests results. Finally, to compare the current design guideline recommendations with the flexure tests results. The most commonly used methods to evaluate Tg Dynamic Mechanical Analysis (DMA) and Differential Scanning Calorimetry (DSC) were used to study Tg. Two off-shelf structural adhesives were investigated to understand their property variation with temperature. Epoxy coupons were cured at different elevated temperature and humidity environments up to 28 days. A combination of two extreme relative humidity of 0 and 100% and variable curing temperatures between 15 to 80°C were considered. From a test matrix of 300 DMA and over 250 DSC coupons these conclusions were drawn. First, ambient cured thermosets have a linear relationship between Tg and curing temperature, but Tg is reduced if a certain temperature is reached. Second, a fully cured adhesive requires heating treatment. Without a curing regime, designed Tg may never be achieved. Finally, curing time is crucial at the low curing temperatures while it is less significant at the higher curing temperature. The results of Tg investigation were used to select appropriate curing temperature that the adhesives resistance to temperature can be maximised without damaging the mechanical properties. The study helps designs to understand and assess the behaviour of these two adhesives when they are exposed to extreme temperatures. The study increases the awareness that a fully cured adhesive may never be achieved at ambient or low temperatures. It is important to find the mechanical properties and Tg when the coupons are exposed to the same curing temperature. To investigate the influence of glass transition temperature Tg improvement on the performance of EB-FRP strengthened steel structures in flexure at ambient and elevated temperature, nine three metre length beams were designed to behave as a concrete-steel composite bridge deck. The beams were tested in four-point bending. Lap shear, DMA test, and pull-off adhesion samples were prepared and cured at the same conditions and tested at ambient temperature. Six beams were tested under only mechanically loading at ambient temperature, including the control specimen. Five beams were tested at ambient temperature to show the effects of adhesive curing on FRP strengthened sections. A significant increase of load capacity of the adhesive joints was achieved due to the curing of the joints at elevated temperature. The failure occurred was in the same manner. An increase in the load capacity was observed with increasing curing temperature. An increase of approximately 25% was noticed in the ultimate load capacity of the specimens cured at 50°C compared to the specimens cured at 30°C. The load capacity of lap-shear specimens cured at 50°C was 28% higher than the specimens cured at 30°C. Three specimens were tested under mechanical and thermal loading. A bespoke thermal chamber was designed and fabricated to apply a controlled thermal loading. The beams were loaded mechanically up to 350kN, first. The temperature of the specimens was then increased at a rate of 0.8°C/min. The sustained load 350kN remained constant during the heating phase. Digital Image Correlation (DIC) technique was used to detect the slippage of the tip of the FRP plates. The only specimen cured at 30°C showed relatively poor performance compared to the two specimens cured at 50°C. The plate ends started to slip when the adhesive storage modulus from the DMA runs reduced approximately by 15 and 18% for the beams cured at 30 and 50°C respectively. Pull-off adhesion tests confirmed that adequate surface preparation of over 25 MPa was achieved The flexural model for the composite steel section represented to predicate load-deflection behaviour of the specimens using semi-experimental constitutive material law. The model successfully predicts the load-deflection behaviour of specimens, considering the strain hardening contribution. A bond stress analysis is also presented, which counts for the effect of FRP plate moment effect. The experimental and theoretical FRP plate slippage assuming only adhesive degradation with temperature are compared. The analytical bond models cannot predict the experimental failure because the linear elastic material properties were assumed and the failure was adhesion.

[pt] O principal objetivo deste trabalho foi avaliar o comportamento mecânico de misturas asfálticas reforçadas com geogrelhas. Inicialmente foram previstos ensaios a serem executados em um modelo físico de verdadeira grandeza. Entretanto, devido a um comprometimento estrutural localizado num dos componentes deste modelo físico durante a realização dos ensaios, optou-se por interromper a execução destes e então, elaborar um programa experimental de laboratório, que consistia da extração de amostras deste modelo físico de verdadeira grandeza e moldagem de corpos de prova por amassamento através de compactador giratório. Cada conjunto de amostras (extraídas e moldadas) possuía corpos de prova sem ou com reforço, onde foram estudados dois tipos de geogrelha (de fibra de vidro e poliéster). Foram realizados os ensaios de Resistência à Tração por Compressão Diametral, Módulo de Resiliência, Fadiga por compressão diametral sob carga controlada e Tração em Disco Circular com Fenda. Os resultados dos ensaios mostraram que a presença do reforço de geogrelha melhorou o comportamento mecânico das misturas asfálticas, com a tendência de maior resistência à fratura, fato este evidenciado principalmente pelo ensaio de Tração em Disco Circular com Fenda, onde tais corpos de prova não atingiram o critério de finalização do ensaio (redução da carga aplicada a 0,10 kN). Nos ensaios de fadiga constatou-se que a melhor influência das geogrelhas ocorre para os menores níveis de tensão aplicada, sendo que nesta condição é permitido um maior período para as geogrelhas se deformarem, condição essencial para sua atuação como elemento com a função de atrasar a propagação de trincas. Constatouse uma melhoria significativa nos resultados obtidos com as amostras reforçadas com as grelhas, tendo as amostras com camada de geogrelha de poliéster apresentado os melhores resultados. / [en] The objective of this study was to evaluate the mechanical behavior of geogrid reinforced asphalt mixtures. Initially tests were planned to be executed on a physical model, however, this tests had to be stopped due to structural problems. Samples were extracted from the physical model and samples were shaped through gyratory compaction, both for analyze the mechanical laboratory tests. Tensile Resistance (Brazilian Test), Resilient Modulus, Fatigue (controlled load) and Disk-Shaped Compact Tension Geometry Tests were carried out in extracted and shaped samples, without reinforcement and with the reinforcement of two geogrid types (fiberglass and polyester). The reinforcement improved the mechanical behavior of asphalt mixtures, with the trend of greater resistance to fracture, and this was evidenced by Disk-Shaped Compact Tension Geometry Tests, where the final criterion of the test was not reached (reduction of the applied load of 0.10 kN). The influence of geogrid is better for lower applied stress levels according with the Fatigue Tests. This condition allows the geogrid to deform for a long period, witch is essential for the performance as an element for delay crack propagation. There was a significant improvement in the results obtained with the reinforced samples, for both geogrids studied, but the polyester geogrid reached better results when compared to fiberglass geogrid.

Cette thèse s’inscrit dans le cadre d’un projet GREENANONANO né d’un partenariat entre le Luxembourg Institute of Science and Technology (LIST), Goodyear et l’Université de Lorraine dans le but de relever un défi technologique concernant l’augmentation des performances des propriétés viscoélastiques de la gomme utilisée dans les pneumatiques. Cette gomme est un composite constitué d’un élastomère (caoutchouc naturel) renforcé par la silice et le noir de carbone. La dispersion de ces charges n’est pas optimale et tend à dégrader les propriétés mécaniques et électrostatiques et donc les performances des pneus. Faces à ces limitations industrielles, l’utilisation d’autres types de renforts tels que les nanotubes de carbone devient une alternative crédible. Etant donné que les nanotubes de carbone (NTCs) ont tendance à s’organiser en fagots, le problème de la dispersion reste à résoudre. Nous proposons dans cette thèse la mise en place d’un matériau biphasé constitué de silice mésoporeuse naturelle, appelée diatomite, sur laquelle ont été synthétisés des NTCs. La grande surface spécifique de la diatomite offre la possibilité d’y faire croître une grande densité de NTCs et d’accroître significativement la surface de contact avec la matrice polymère. Cette thèse multidisciplinaire a débuté par la synthèse de nanoparticules métalliques par ALD pour la croissance de NTCs, suivie d’un développement du procédé de croissance de NTCs sur la diatomite. L’intégration réussie des charges biphasées obtenues au sein de matrices polymériques (élastomère, thermoplastique) a permis de mesurer les propriétés mécaniques, thermiques et électriques des nanocomposites ainsi fabriqués / This thesis is part of the GREENANONANO project ensuing from a partnership between the Luxembourg Institute of Science and Technology (LIST), Goodyear Company and Université de Lorraine, in order to address a technological challenge for increasing tires performances. The latter are directly related to the viscoelastic properties of the rubber used in tires. This gum is a composite material made by mixing an elastomeric matrix (natural rubber) and fillers (silica and carbon black). Nowadays, the filler dispersion is not optimal, which degrades the mechanical and electrostatic properties and therefore performances of tires. All these industrial limitations require the use of other types of reinforcing agents such as carbon nanotubes. Since carbon nanotubes tend to be organized into bundles, the dispersion problem still exists. We therefore propose in this thesis the synthesis of a biphased material composed by diatomite particles (natural mesoporous silica) on which are grown carbon nanotubes (CNTs). The high surface area of diatomite offers the possibility of growing a high density of CNTs, increasing the contact area with the polymer matrix. This multidisciplinary thesis started with the synthesis of metal nanoparticles by Atomic Layer Deposition (ALD) to catalyse the growth of CNTs and then a process was developed to grow CNTs on diatomite particles. The successful integration of the resulting biphased particles in polymer matrices (elastomer, thermoplastic) allowed to measure the mechanical, thermal and electrical properties of the nanocomposites thus produced

O efeito placebo tem sua origem atrelada aos estudos ligados às ciências médicas e farmacológicas e, basicamente, consiste na capacidade de produtos inertes produzirem efeitos por meio do seu uso ou consumo. Esse efeito passou a fazer parte do escopo do Marketing em 2005, quando estudos mostraram a capacidade do preço gerar modificações sobre o desempenho de um produto. A ideia do efeito placebo desencadeado pelo preço dos produtos está ancorada no fato das crenças globais, que associam preço baixo a produtos de má qualidade, anteciparem as expectativas do consumidor acerca da resposta do produto e, a partir disso, alterarem o seu desempenho. Nessa mesma linha, o estereótipo do país de origem também se apresenta como uma crença global, em que produtos oriundos de países com estereótipo negativo são associados a produtos inferiores e de má qualidade. Sendo assim, esta pesquisa analisou a ocorrência do efeito placebo desencadeado pelo país de origem do produto, analisando, ainda, a interação da força das expectativas e do preço do produto na geração deste efeito. Para tanto, três estudos experimentais foram operacionalizados. O primeiro estudo apresentou as testagens iniciais sobre o efeito placebo gerado pelo país de origem e mostrou que o país de origem com estereótipo negativo é capaz de gerar um efeito placebo negativo sobre o desempenho do produto. Não foi identificado, no entanto, a ocorrência de efeito placebo gerado pelo estereótipo positivo do país de origem. No segundo estudo, analisou-se o efeito placebo do país de origem em cenário de alta e baixa expectativa. Como resultado, obteve-se, em cenário de baixa expectativa, a ocorrência de efeito placebo negativo gerado pelo estereótipo negativo do país de origem. Já em cenário de alta expectativa, os resultados indicam que o fortalecimento das expectativas eliminou o efeito placebo negativo e, além disso, promoveu a ocorrência de um efeito placebo positivo gerado pelo estereótipo positivo do país de origem. O último estudo observou a interação do país de origem e do preço do produto sobre a geração de efeito placebo. Os resultados mostram que, em cenário de preço baixo, há efeito placebo negativo gerado pelo país de origem com estereótipo negativo, mas não foi observada a ocorrência de efeito placebo positivo gerado pelo estereótipo positivo do país de origem. Já, em cenário de preço alto, não se observou a ocorrência de nenhum efeito placebo, nem positivo, nem negativo. Ou seja, o preço elevado do produto foi capaz de anular o efeito placebo negativo gerado pelo estereótipo negativo do produto, mostrando a capacidade do preço em compensar os efeitos negativos causados pelo país de origem com imagem desfavorável. Com base nisso, os achados desta tese contribuem para o avanço teórico dos estudos sobre efeito placebo em Marketing, uma vez que adicionam o país de origem como um elemento gerador deste tipo de efeito e, ao analisar a interação do país de origem com o fortalecimento das expectativas e o preço do produto, confirmam as bases conceituais sobre a relação entre esses elementos. Além disso, seus achados, em termos gerenciais, podem promover reflexões por parte das organizações que compõem o seu mix de produtos com bens importados e também que operaram no exterior e fazem investimentos externos diretos em diversas partes do mundo. / The placebo effect has its origin linked to studies related to medical and pharmacological sciences and basically consists in the ability of inert products to produce effects through its use or consumption. This effect became part of the Marketing scope in 2005 when studies showed the ability of pricing to generate changes on the performance of a product. The idea of the placebo effect triggered by product price is anchored on the fact that global beliefs, which associate low price to low quality products, anticipate consumer expectations about the response of the product and, from there, change its performance. Along the same line, the stereotype of the country of origin also presents itself as a global belief in that products from countries with negative stereotypes are associated with inferior and bad quality products. Thus, this research analyzed the occurrence of the placebo effect triggered by the country of origin of the product, also analyzing the interaction of the strength of expectations and of product price in the generation of this effect. For this purpose, three experimental studies were operationalized. The first study presented initial testings on the placebo effect generated by the country of origin and showed that the country of origin with negative stereotypes is able to generate a negative placebo effect on product performance. However, the occurrence of the placebo effect generated by positive stereotypes in the country of origin was not identified. In the second study, the placebo effect of the country of origin in a scenario of high and low expectations was analyzed. As a result, in a scenario of low expectations, the occurrence of a negative placebo effect generated by the negative stereotype of the country of origin was obtained. However, in a scenario of high expectations, results indicate that the strengthening of the expectations eliminated a negative placebo effect and in addition, promoted the occurrence of a positive placebo effect generated by the positive stereotype of the country of origin. The last study observed the interaction of the country of origin and the price of the product upon the generation of the placebo effect. The results show that in a scenario of low price, there is a negative placebo effect generated by the country of origin with a negative stereotype, but the occurrence of a positive placebo effect generated by the positive stereotype of the country of origin was not observed. However, in a scenario of high prices, there was no occurrence of a placebo effect, whether positive or negative. In other words, the high price of the product was able to cancel the negative placebo effect generated by the negative stereotype of the product, showing the capacity of the price to compensate for the negative effects caused by the country of origin with an unfavorable image. Based on this, this thesis’ findings contribute to the theoretical progress on the studies about the placebo effect in Marketing, once the country of origin is added as a generating element of this type of effect, and when analyzing the interaction of the country of origin with the strengthening of expectations and the price of the product, the conceptual foundations about the relationship between these elements are confirmed. Moreover, its findings in management terms can promote reflections by organizations that compose the product mix with imported goods and also that operate overseas and make foreign direct investments in various parts of the world.

L'alliage AA2198 est un alliage à durcissement structural qui est principalement utilisé pour des applications aéronautiques. La phase anisotrope T1 - Al2LiCu est la principale phase durcissante dans ce système. L'objectif de cette étude est de comprendre les mécanismes de durcissement, en termes d'interaction dislocations/précipités, associés à la phase T1 qui précipite sous forme de plaquettes. La première étape consiste au développement d'une méthode de caractérisation adaptée à la phase T1 (caractérisation du diamètre, de l'épaisseur et de la fraction volumique des plaquettes). Le traitement thermomécanique est ajusté afin de varier les paramètres de la phase T1 de manière indépendante et la limite d'élasticité est systématiquement mesuré ce qui permet de mieux comprendre le lien entre la microstructure de T1 et la limite d'élasticité. La base de données expérimentale qui est générée permet de tester et d'améliorer les modèles de limite d'élasticité existants. Une approche énergétique du mécanisme de cisaillement permet de modéliser de manière précise la limite d'élasticité pour un grand nombre de microstructures. Le mécanisme de cisaillement permet d'expliquer la décroissance en limite d'élasticité après le pic de durcissement. L'observation des phénomènes de plasticité associés à la phase T1, par l'étude des bandes cisaillements et du comportement en écrouissage, est la dernière étape de ce travail. L'ensemble des résultats permet d'identifier une transition cisaillement/contournement qui intervient longtemps après le pic de durcissement. / The age-hardening AA2198 alloy is mainly used in aeronautic applications. The anisotropic T1 - Al2LiCu phase gives the main contribution to strengthening in this system. The main objective of this study is to understand the strengthening mechanisms in terms of interactions between the dislocations and the T1 plate-like precipitates. The first step consists in the development of a characterization procedure adapted to the T1 phase (characterization of the diameter, thickness and volume fraction of the T1 plates). The thermo-mechanical treatment is adapted in order to vary the T1 parameters independently and the yield strength evolution is systematically measured and that permits the investigation of the relationship between the T1 microstructure and the yield strength variations. The experimental data base that is generated allows testing and improving the existing yield strength models. An energetic approach of the shearing mechanisms is used to model precisely the yield strength evolution for a high number of microstructures. The decrease in yield strength after the peak is solely explained by invoking the shearing mechanism. The investigation of the plasticity phenomenon associated to the T1 phase, with the study of the shear bands and of the work hardening behavior, is the last step of this work. A shearing-to-by-passing transition is found to occur for long-over ageing times.

O efeito placebo tem sua origem atrelada aos estudos ligados às ciências médicas e farmacológicas e, basicamente, consiste na capacidade de produtos inertes produzirem efeitos por meio do seu uso ou consumo. Esse efeito passou a fazer parte do escopo do Marketing em 2005, quando estudos mostraram a capacidade do preço gerar modificações sobre o desempenho de um produto. A ideia do efeito placebo desencadeado pelo preço dos produtos está ancorada no fato das crenças globais, que associam preço baixo a produtos de má qualidade, anteciparem as expectativas do consumidor acerca da resposta do produto e, a partir disso, alterarem o seu desempenho. Nessa mesma linha, o estereótipo do país de origem também se apresenta como uma crença global, em que produtos oriundos de países com estereótipo negativo são associados a produtos inferiores e de má qualidade. Sendo assim, esta pesquisa analisou a ocorrência do efeito placebo desencadeado pelo país de origem do produto, analisando, ainda, a interação da força das expectativas e do preço do produto na geração deste efeito. Para tanto, três estudos experimentais foram operacionalizados. O primeiro estudo apresentou as testagens iniciais sobre o efeito placebo gerado pelo país de origem e mostrou que o país de origem com estereótipo negativo é capaz de gerar um efeito placebo negativo sobre o desempenho do produto. Não foi identificado, no entanto, a ocorrência de efeito placebo gerado pelo estereótipo positivo do país de origem. No segundo estudo, analisou-se o efeito placebo do país de origem em cenário de alta e baixa expectativa. Como resultado, obteve-se, em cenário de baixa expectativa, a ocorrência de efeito placebo negativo gerado pelo estereótipo negativo do país de origem. Já em cenário de alta expectativa, os resultados indicam que o fortalecimento das expectativas eliminou o efeito placebo negativo e, além disso, promoveu a ocorrência de um efeito placebo positivo gerado pelo estereótipo positivo do país de origem. O último estudo observou a interação do país de origem e do preço do produto sobre a geração de efeito placebo. Os resultados mostram que, em cenário de preço baixo, há efeito placebo negativo gerado pelo país de origem com estereótipo negativo, mas não foi observada a ocorrência de efeito placebo positivo gerado pelo estereótipo positivo do país de origem. Já, em cenário de preço alto, não se observou a ocorrência de nenhum efeito placebo, nem positivo, nem negativo. Ou seja, o preço elevado do produto foi capaz de anular o efeito placebo negativo gerado pelo estereótipo negativo do produto, mostrando a capacidade do preço em compensar os efeitos negativos causados pelo país de origem com imagem desfavorável. Com base nisso, os achados desta tese contribuem para o avanço teórico dos estudos sobre efeito placebo em Marketing, uma vez que adicionam o país de origem como um elemento gerador deste tipo de efeito e, ao analisar a interação do país de origem com o fortalecimento das expectativas e o preço do produto, confirmam as bases conceituais sobre a relação entre esses elementos. Além disso, seus achados, em termos gerenciais, podem promover reflexões por parte das organizações que compõem o seu mix de produtos com bens importados e também que operaram no exterior e fazem investimentos externos diretos em diversas partes do mundo. / The placebo effect has its origin linked to studies related to medical and pharmacological sciences and basically consists in the ability of inert products to produce effects through its use or consumption. This effect became part of the Marketing scope in 2005 when studies showed the ability of pricing to generate changes on the performance of a product. The idea of the placebo effect triggered by product price is anchored on the fact that global beliefs, which associate low price to low quality products, anticipate consumer expectations about the response of the product and, from there, change its performance. Along the same line, the stereotype of the country of origin also presents itself as a global belief in that products from countries with negative stereotypes are associated with inferior and bad quality products. Thus, this research analyzed the occurrence of the placebo effect triggered by the country of origin of the product, also analyzing the interaction of the strength of expectations and of product price in the generation of this effect. For this purpose, three experimental studies were operationalized. The first study presented initial testings on the placebo effect generated by the country of origin and showed that the country of origin with negative stereotypes is able to generate a negative placebo effect on product performance. However, the occurrence of the placebo effect generated by positive stereotypes in the country of origin was not identified. In the second study, the placebo effect of the country of origin in a scenario of high and low expectations was analyzed. As a result, in a scenario of low expectations, the occurrence of a negative placebo effect generated by the negative stereotype of the country of origin was obtained. However, in a scenario of high expectations, results indicate that the strengthening of the expectations eliminated a negative placebo effect and in addition, promoted the occurrence of a positive placebo effect generated by the positive stereotype of the country of origin. The last study observed the interaction of the country of origin and the price of the product upon the generation of the placebo effect. The results show that in a scenario of low price, there is a negative placebo effect generated by the country of origin with a negative stereotype, but the occurrence of a positive placebo effect generated by the positive stereotype of the country of origin was not observed. However, in a scenario of high prices, there was no occurrence of a placebo effect, whether positive or negative. In other words, the high price of the product was able to cancel the negative placebo effect generated by the negative stereotype of the product, showing the capacity of the price to compensate for the negative effects caused by the country of origin with an unfavorable image. Based on this, this thesis’ findings contribute to the theoretical progress on the studies about the placebo effect in Marketing, once the country of origin is added as a generating element of this type of effect, and when analyzing the interaction of the country of origin with the strengthening of expectations and the price of the product, the conceptual foundations about the relationship between these elements are confirmed. Moreover, its findings in management terms can promote reflections by organizations that compose the product mix with imported goods and also that operate overseas and make foreign direct investments in various parts of the world.

Este estudo apresenta os resultados de uma investigação experimental constituída de três séries de ensaio, cada uma envolvendo dois modelos: um pilar básico de concreto armado, representando o pilar a ser reforçado e um pilar reforçado por camisa de concreto de alto desempenho com várias características. Todos os pilares básicos tinham a seção quadrada de 150 mm x 150 mm com altura de 1200 mm. Eles foram produzidos com concreto de 18 MPa de resistência nominal à compressão, armadura longitudinal com quatro barras de 8 mm de diâmetro e armadura transversal com estribos de 6.3mm de diâmetro com espaçamento de 90 mm. Os parâmetros que foram variados nas camisas de reforço foram: a) dois valores de espessura (tj); b) três valores de taxa de armadura transversal (*sw) utilizando telas soldadas ou armadura de estribos; c) adição de fibras curtas de aço. A resistência nominal à compressão do concreto utilizado em todas as camisas foi de 65 MPa, caracterizando-se portanto um concreto de alta resistência. Os pilares foram submetidos à compressão axial por meio de uma máquina hidráulica servo-controlada. Os ensaios foram realizados com controle de deslocamento, adotando-se uma velocidade de 0.005mm/s para o deslocamento do pistão. A força aplicada e as deformações continuaram sendo medidas após o alcance da força de ruína, para se avaliar o comportamento pós-pico, até se atingir uma força residual de cerca de 50% da força de pico. Modelos de cálculo da resistência última dos pilares reforçados foram analisados. Também foram testados modelos de confinamento e ductilidade para os elementos reforçados. / This study presents the results of an experimental investigation in three series of tests, each one involving two models: a basic reinforced concrete column, which represents the column to ge strengthened, and an identical basic column strengthned by a high-performance concrete jacket with variable characteristics. All the basic columns had a 150 mm x 150 mm square section and a 1,200 mm length. They were made of a 18 MPa nominal strength concrete and reinforced with four 8 mm diameter steel bars and 6.3mm diameter stirrups each. The jacket characteristics varied as follows: a) two thickness values(tj); b) three values of transverse reinforcement ratio (*sw) using welded wire steel meshes or ordinary stirrups; c) addition of short steel fibers. The nominal concrete compressive strength used in all the jackets was 65 MPa, therefore a high-strength concrete. The columns were subjected to monotonic axial compression by means of a servo-controlled hydraulic machine. A displacement increasing rate of 0.005 mm/sec at the top of the column was adopted. Load and strain measurements continued after the ultimate load to evaluate the post-peak behavior, up to a residual load-bearing capacity of about 50% of the peak load. Several calculation hypotheses were tested to evaluate the ultime strength of the rehabilitated columns. Also confinement mechanisms and ductility of the members were analyzed.

O confinamento de pilares de concreto por meio de camisas de aço ou compósitos possui uma função importante na preservação, recuperação e reforço de estruturas, pois proporciona aumento de resistência e ductilidade desses elementos estruturais. Porém, grande parte dos modelos existentes apresenta limitações na previsão do comportamento do concreto confinado, principalmente por serem dependentes do tipo de confinamento. Portanto, este trabalho apresenta um modelo para descrição do comportamento tensão-deformação do concreto submetido a qualquer tipo de confinamento uniforme, ativo ou passivo, e confinado com diferentes materiais confinantes - aço ou compósitos. O modelo constitutivo associa plasticidade e dano a fim de prever adequadamente a resistência, deformabilidade e redução de rigidez elástica do concreto confinado. O modelo é desenvolvido para um processo incremental explícito de implementação, permitindo, portanto, o seu desenvolvimento em qualquer tipo de planilha. Finalmente, o modelo foi validado por meio de um conjunto representativo de experimentos encontrados na literatura. / Confinement of concrete columns through steel or composites jackets has an important function in the preservation, recovery and strengthening of structures, because it provides increased strength and ductility of these structural elements. However, most of the existing models have limitations in the prediction of the behavior of confined concrete, mainly because they are dependent on the type of confinement. This work presents a model for the description of the stress-strain behavior of the concrete submitted to any type of uniform confinement, active or passive, and confined with different confinement materials, steel or composites. The constitutive model associates plasticity and damage in order to predict with accuracy the strength, ultimate strain and reduction of elastic stiffness of the confined concrete. The model is developed by an explicit incremental implementation process allowing, therefore, its development in any type of spreadsheet. Finally, the model was validated through a representative set of experiments found in the literature.

Este trabalho aborda o efeito do confinamento desenvolvido em pilares de concreto armado reforçados com compósitos de fibras de carbono. Por meio do encamisamento é possível mobilizar o confinamento passivo do concreto, restringindo sua expansão lateral. Com o efeito do confinamento o concreto apresenta significativos ganhos de resistência e ductilidade. Efetuou-se uma análise experimental com pilares de seção transversal circular utilizando diferentes taxas de armadura transversal e variando-se o número de camadas do compósito. Observou-se a influência destas variáveis sobre a capacidade resistente e a deformabilidade destes pilares. Com o aumento do número de camadas de compósito ocorreram grandes acréscimos de capacidade resistente, mesmo com taxas de armadura transversal mais elevadas. O aumento da deformação última com o reforço foi grande no caso de pilares não armados. Em pilares com elevada taxa de armadura transversal não ocorreram ganhos significativos na deformação última. Verificou-se que em pilares de concreto armado reforçados com compósito de fibras de carbono, pode-se obter boas previsões do ganho de resistência utilizando-se modelos teóricos de confinamento adequados e a sobreposição de pressões laterais da camisa de reforço e da armadura transversal no núcleo. Foram ensaiados também pilares de seção transversal quadrada sem armaduras para verificar o efeito da forma da seção transversal. Observou-se que em seções quadradas a pressão lateral efetiva é menor se comparada com pilares de seção circular. / This work deals with the effect of confinement in reinforced concrete columns strengthened with carbon fiber composites. By wrapping, it is possible to mobilize the passive confinement of the concrete, restricting its lateral expansion. With the confinement, the concrete shows substantial gains in resistance and ductility. An experimental analysis of circular columns was carried out making use of different rates of transverse steel and numbers of composite layers. The influence of these variables over the load carrying capacity and deformability of these columns was observed. With an increased number of layers of the composite, there was a great increase in the load carrying capacity, even at high transverse steel rates. The increase in the ultimate strain given by the strengthening was great with unreinforced concrete columns. In columns with a high transverse steel rate there were no important gains in the ultimate strain. It was observed that in reinforced concrete columns strengthened with carbon fiber composites, one can very well foresee the gain in strength by using adequate analytical models of confinement and the overlaying of lateral pressures from the composite jacket and the transverse steel in the central core. Square columns without reinforcement bars were also subject to testing so as to investigate the effect of the shape of the cross-section. It was observable that in square sections the real lateral pressure is smaller when compared to circular columns.