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En el presente artıculo se recopilan los resultados de una reciente campaña experimental sobre el efecto de la velocidad de solicitación y del angulo de inclinación, en ensayos de arrancamiento de fibras de acero de una matriz de hormigon. Para ello, se obtuvieron probetas de placas fabricadas con hormigón auto-compactante de 86 MPa de resistencia. En el programa experimental se emplearon fibras de acero de extremos conformados de nueva generación, sección circular, con ´ 60 mm de longitud y una relación de aspecto de 80. Los ensayos se llevaron a cabo con fibras de extremos conformados ´ y fibras lisas, obteniendo estas últimas mediante el corte del gancho de las primeras. Para ambos tipos, la longitud de ´ fibra embebida en el hormigón fue de 20 mm, estudiando la influencia de la inclinación de la fibra para valores de 0 ´ o, 30o y 60o. Las fibras lisas se obtuvieron cortando el extremo conformado de las anteriores. Los ensayos se realizaron a tres velocidades de solicitación 0.01, 0.1 y 1 mm/s. Como resultado, se obtuvo que las fibras más inclinadas incrementaron la ´ carga necesaria para arrancarlas de la matriz de hormigón en todos los casos, aunque de manera más pronunciada en las ´ fibras lisas. Además, el incremento en la velocidad de solicitación hizo que la carga máxima en el ensayo se incrementará para el caso de las fibras lisas, mientras que permaneció prácticamente estable para las fibras conformadas., This paper summarizes the results obtained in a recent experimental campaign on the effect of the loading pullout rate and the inclination angle of the steel fiber pullout test. For that purpose, specimens were obtained from a self-compacting concrete with a compressive strength of 86 MPa. In the experimental program hooked-end steel fibres of new generation, of circular cross section, length of 60 mm and aspect ratio of 80, were used. Tests were executed with both hooked-end and smooth fibers, being these last ones obtained from the first ones by cutting the hooked-end. For both type of fibers, their embedment length into concrete was 20 mm, and the influence of fiber inclination angle was investigated by adopting values of 0o , 30o and 60o . The tests were performed at displacement rates of 0.01, 0.1 and 1 mm/s. As a result, the peak pullout load increased with the inclination angle, in particular for the smooth series. Furthermore, higher displacement rates produced higher peak forces for the pullout of the smooth fibers, while the peak remained almost stable for hook-end fibers.

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In the present study, the effectiveness of a fibre as an element for transferring stresses across cracks under a sustained load was assessed. Single fibre pull-out creep tests were performed, in which fibre slip was monitored as a function of the time. The influence of the fibre orientation angle (0, 30 and 60 degrees), as well as pre-imposed fibre slip levels, spr, 0.3 and 0.5 mm on the creep response was investigated. Additionally, instantaneous fibre pull-out tests were carried out on undamaged-bond specimens in order to quantify the effects of the pull-out creep behaviour. The damage introduced by the pre-slip levels in the bond of the fibre/matrix interface influenced the long-term fibre pull-out behaviour and, consequently, accelerated the creep rate. However, the assembled pull-out creep behaviour did not differ considerably from the instantaneous pull-out behaviour for the adopted pre-imposed fibre slip levels., This work is supported by the FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the project 18 SlabSys-HFRC-PTDC/ECM/120394/2010. The authors would like to acknowledge the materials supplied by Radmix and Maccaferri (fibres), SECIL (cement), SIKA and BASF (superplasticizers), Omya Comital (limestone filler), and Pegop (Fly ash)., info:eu-repo/semantics/publishedVersion

This work presents the results of an extensive experimental program that aims to study the long-term behaviour of cracked steel fibre reinforced self-compacting concrete (SFRSCC). At the micro-level, a series of single fibre pull-out creep tests were performed, and the fibre slip was monitored as a function of time. The influence of fibre orientation angle (0, 30 and 60 degrees), as well as pre-imposed fibre slip levels 0.3 and 0.5 mm on the creep behaviour was investigated. At the composite level, prismatic specimens were extracted from a SFRSCC panel, having in consideration the concrete flow direction. The specimens were pre-cracked up to 0.3 and 0.5 mm and subjected to a sustained flexural loading. In this stage, the influence of the pre-crack level and fibre orientation on the long-term crack opening was appraised. Furthermore, instantaneous fibre pull-out tests and bending tests were performed on undamaged specimens to quantify the effects of the creep phenomenon. It was found that a higher damage level in the specimens accelerated the creep rate. Moreover, the creep performance of the SFRSCC was influenced by the fibre orientation. Finally, the assembled creep curves did not differ considerably from the instantaneous behaviours for the adopted pre-damaged levels., T his work is supported by the FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the project SlabSys - HFRC - PTDC/ECM/120394/2010. Radmix and Maccaferri (fibres), SECIL (cement), SIKA and BASF (superplasticizers), Omya Comital (limestone filler), and Pegop (Fly ash). Civitest Company for the development of the Steel Fibre Reinforced Self - Compacting Concrete used in this work

Portland cement concrete is the most used building material in the world. However, its manufacture is energy-intensive and it is susceptible to harsh environments. Alternative binder systems without ordinary Portland cement, such as geopolymers or alkali-activated materials, are recently new in the Civil Engineered world. These alternative binder systems seek, among other characteristics, improved durability and environmental efficiency. The attaining of strain hardening and multiple cracking typical of Strain Hardening Cementitious Composites (SHCC) using these alternative binder systems is very attractive from a conceptual point of view, since additional endurance to certain harsh or extreme environments, as well as enhanced durability, are usually expected as two of the main outcomes. In the present work, the behaviour of two different composites was studied: an existing Engineered Cementitious Composite (ECC) and a new composite based on an alternative binder prepared with metakaolin. Polyvinyl alcohol (PVA) fibres were used in both materials. A series of experiments, including compressive and direct tensile testing were carried out to characterize and compare the mechanical properties of both materials. The results showed that the alternative binder composite, when subjected to uniaxial tension, developed multiple cracks at steadily increasing tensile stress and strain, which is also typical of ECCs showing strain hardening behaviour. The development of fibre reinforced geopolymer or alkali-activated materials showing strain hardening ability in tension may still be considered as a novel research topic, with great potential for creating new and interesting developments for Civil Engineering and structural applications, particularly the ones subjected to harsh environments.

Modern structures are being exposed to severe environments and the lack of durability is one of the most serious problems in concrete infrastructures. Structural concrete exposed to marine environment deserves special attention as the sea salts chemically react with the cement matrix and the steel reinforcement which results in loss of strength, cracking, spalling, etc. The challenges of Civil Engineering, especially within the structures in extreme environments, pose considerable expectations with regards to the development of fibre reinforced materials for the development of more resistant and durable solutions. In the present work, the behaviour of an Engineered Cementitious Composite (ECC) was studied. All the specimens prepared were cured in 4 types of environments: exposed to air (20ºC of temperature and 60% of humidity) immersed in tap water, immersed in salted water and immersed in seawater, all at an average temperature of 18ºC. A series of experiments, including compressive and direct tension tests were carried out to characterize the mechanical properties of the ECC materials while exposed to different environments. The most important characteristic of ECC, which include multiple-cracking behaviour at increasing tensile strains when subjected to increasing tensile loading, was confirmed in all types of curing environments. In all cases the cementitious composites performed well with regards to the strain hardening behaviour typically observed in these materials, although the cracking processes have shown different characteristics. Due to the ability of the material to control crack opening below extremely low values, typically under 100 µm, the durability of structures can be significantly improved when ECC materials are used in the in marine environments. It was shown also that the salted water does not represent well the effect of seawater while characterising ECC mechanical characteristics in the laboratory., The authors acknowledge the material suppliers Secil, Civitest, Sika, Saint-Gobain (Fibraflex) and Eurocálcio – Calcários e Inertes SA for providing the materials used in this study.

By taking advantage of the appropriate use of cement and polymer based materials and advanced computational tools, a pre-fabricated affordable house was built in a modular system. Modular system refers to the complete structure that is built-up by assembling pre-fabricated sandwich panels composed of steel fibre reinforced self-compacting concrete (SFRSCC) outer layers that are connected by innovative glass fibre reinforced polymer (GFRP) connectors, resulting in a panel with adequate structural, acoustic, and thermal insulation properties. The modular house was prepared for a typical family of six members, but its living area can be easily increased by assembling other pre-fabricated elements. The speed of construction and the cost of the constructive elements make these houses competitive when compared to traditional solutions. In this paper the relevant research subjacent to this project (LEGOUSE) is briefly described, as well as the construction process of the built real scale prototype.

Neste trabalho apresentam-se os principais resultados do estudo da influência de certo tipo de exposições ambientais no comportamento pós-fissurado de betão auto-compactável reforçado com fibras de aço, BACRFA. Para o devido efeito foram produzidos diversos provetes prismáticos de BACRFA. Inicialmente os provetes foram sujeitos a ensaios cíclicos de flexão em três pontos, com o objetivo de se induzir dois níveis de pré-fissuração distintos, respetivamente, com uma abertura de fenda de 0.3 e 1.0 mm. Posteriormente, os provetes pré-fissurados foram submetidos a três tipos de exposição ambiental durante um período de dezoito meses. Por fim caracterizou-se o desempenho mecânico dos provetes após exposição ambiental.

1 Resumo No âmbito do estágio do 4º semestre do Mestrado em Recursos Florestais, realizado em parceria com a Organização Florestal Atlantis, foi elaborado um estudo para avaliar o efeito de diferentes tipos de mobilização no solo e no crescimento das plantas em quatro áreas de estudo. Os objetivos do estágio foram a instalação de ensaios com diferentes mobilizações de solo para posterior comparação da taxa de sobrevivência e crescimento do eucalipto (Eucalyptus globulus Labill.). Foi igualmente analisado a produtividade das operações (h/ha) de mobilização dos solos (ripagem/gradagem vs mobilização à “cava”) e respetivos custos de operação. Foi ainda avaliado o efeito do tipo de mobilização no teor de matéria orgânica no solo e consequentemente na fertilidade do solo. Os resultados mais evidentes foram que a mobilização à “cava” é mais onerosa e demora mais tempo a ser realizada, logo com menor produtividade. Este tipo de mobilização leva à inversão dos horizontes do solo e diminuição da matéria orgânica disponível para as plantas e consequente redução de nutrientes e da fertilidade do solo. Os dados recolhidos até ao momento também comprovam que o crescimento das plantas nos terrenos sujeitos a mobilização à “cava” é menor. A suscetibilidade à erosão é igualmente maior quando comparada com as operações de gradagem e ripagem realizadas. Os resultados das amostras de solo comprovam igualmente que as parcelas onde foi realizada a mobilização à “cava” apresentam valores mais baixos de matéria orgânica e de azoto. Foi igualmente realizado um levantamento dos custos das operações junto de empresas silvícolas e posteriormente comparadas com as tabelas da Comissão de Acompanhamento para as Operações Florestais, e verificou-se que existe discrepâncias no que está a ser praticado no mercado da região Centro. A mobilização à “cava” apresenta menor rentabilidade, menor crescimento e maior impacto no solo. Estes resultados estão de acordo com a decisão do Instituto da Conservação da Natureza e das Florestas (ICNF), na medida em que este tipo de mobilização é proibida. PALAVRAS-CHAVE: Eucalyptus globulus, mobilizações de solo, tempos de trabalho, crescimento/produtividade e custos. 2 Abstract Under the Master of half of the 4th stage in Forest Resources, in partnership with the Organização Florestal Atlantis, we designed a study to evaluate the effect of different types of mobilization in the soil and on plant growth in four areas of study. The stage targets have been the test facility with different soil tillage for later comparison of the survival and growth of the common eucalyptus (Eucalyptus globulus Labill.). It was also analyzed the productivity of operations (h / ha) of soil mobilization (ripping / harrowing vs “mobilização à cava”) and its operating costs. It was also evaluated the effect of tilled in organic matter in the soil and consequently soil fertility. The most obvious results were that the “mobilização à cava” is more expensive and takes longer time, and lower productivity. This type of mobilization leads to the inversion of soil horizons and decline in organic matter available to the plants and the consequent reduction of nutrients and soil fertility. The data collected so far also show that plant growth on land subject to “mobilização à cava” is lower. The susceptibility to the erosion is also higher when compared with the harrowing and ripping transactions. The results of the soil samples also show that the plots where the “mobilização à cava” was fulfilled presents lower values of organic matter and nitrogen. It has also conducted a survey of the cost of operations along the forestry companies and then compared with the tables of the Comissão de Acompanhamento para as Operações Florestais, and it was found that there is inconsistency in what is being practiced in the central region market. The “mobilização à cava” has lower productivity, lower growth and greater impact on the ground. These results are in agreement with the decision of the Instituto de Conservação da Natureza e das Florestas (ICNF), in the measure that this type of mobilization is prohibited. KEYWORDS: Eucalyptus globulus, soil tillage, working hours, growth / productivity and costs.

Adding fibres to concrete provides several advantages, especially in terms of controlling the crack opening width after the cracking initiation of the composite. However, distribution and orientation of the fibres toward the crack plane are significantly important in order to provide the maximum benefit for controlling crack width. Therefore, in this study, the effect of the fibre distribution and orientation on the tensile behaviour of the steel fibre reinforced self-compacting concrete (SFRSCC) specimens is investigated. For this purpose, cores that are extracted from distinct locations of a panel will be subjected to indirect (splitting) and direct tensile tests. By modeling the splitting tensile test under the finite element framework and by performing an Inverse Analysis (IA), the achieved stress-crack opening relationship (σ-w) is compared with the one obtained directly from the experimental curve obtained in the direct tensile tests., Fundação para a Ciência e a Tecnologia (FCT)

Este trabalho de investigação pretende dar um contributo no campo das técnicas não destrutivas de inspecção e de diagnóstico de vigas antigas de madeira. Para o efeito, correlacionou-se os resultados obtidos através do uso do resistógrafo e da termografia no estudo de uma viga recolhida num edifício de habitação unifamiliar que foi sujeito a um processo de remodelação. Verificou-se que poderá haver uma cerca correlação entre ensaios. Contudo, também se recomenda a realização de um número mais expressivo de ensaios de amostras para ser possível apresentar uma conclusão mais fidedigna. A relevância desta possível correlação prende-se com o facto de poder haver uma alternância na realização destes ensaios consoante os condicionalismos do cenário de obra.

Tabique construction corresponds to a relevant Portuguese heritage. Urban and rural tabique construction exists all over the country. This traditional building technique started to be in disuse after the massive introduction of the reinforced concrete. Therefore, tabique buildings are already aged and, in general, they show signals of degradation. Recent research works have concluded that this degradation stage is essentially caused by the absence of a regular proper maintenance process. The fact that tabique buildings are mainly private property, that there are economical limitations and that there is still a lack of knowledge concerning this traditional building technique, have been the main reasons identified. In order to contribute solving this problem this paper intends to give an input on the characterization of timber frame structural system of tabique walls. In fact, a tabique building element is a structural system formed by a timber frame coated with an earthy render. The elements of the timber frame are nailed to each other. It has been noticed that there are different types of timber frames. Given technical information related to these alternative traditional structural solutions may be helpful in future rehabilitation processes. At the same time, the relevance of this information is even more expressive taking into account the following aspects: a) the access of this type of buildings is in general limited because they are private properties; b) they have been abandoned and, therefore, they are not accessible; c) they became a ruin and they are not safe to be accessed; d) they were demolished.

Schist stone is a traditional building material applied in the Peso da Régua County. This County is located in the Northeast part of Portugal related to the Douro region which is UNESCO World Heritage. Dwellings, earth retaining walls and fencings are the most common constructions built with this type of material. They are vernacular constructions which are very well integrated in the local landscape and its maintenance is important to perform. Thus, a set of building details concerning schist dwelling was surveyed in this research work. This paper intends to disseminate the obtained information, in particular, some structural buildings details. In the structural context, schist masonry walls are the main vertical structural elements. Taking into account that the size, the existence of openings (e.g. window or door), the type of corner and the type of lintel of the openings are some building aspects which may influence the structural behaviour of a traditional masonry schist wall, they are highlighted. We believe that this technical information may give some guidance in future studies focused on modelling (numerically and experimentally) the structural behaviour of this type of traditional building element. info:eu-repo/semantics/publishedVersion

A pedra de xisto é um material natural e local comummente utilizado nas construções tradicionais do Concelho de Peso da Régua. Esta zona do Nordeste Português está inserida na região do Douro que é classificada como Património Mundial pela UNESCO. Os muros de divisão de terrenos, de suporte de terras e os edifícios de construção tradicional são os tipos de construção em que a pedra de xisto é o material dominante. Estas construções são parte integrante da paisagem e do património vernacular local, e por isso devem ser valorizados e preservados. Através deste trabalho de investigação foi possível realizar um levantamento dos edifícios de xisto existentes neste concelho, e reunir um conjunto de informações técnicas e construtivas que os caracterizam. Este artigo pretende divulgar informação técnica relativa a detalhes construtivos deste tipo de construção tradicional, focada principalmente nas suas especificidades estruturais. No contexto estrutural, as paredes de alvenaria de pedra de xisto são os elementos estruturais verticais principais. As dimensões e constituição das paredes, dos vãos de janela e de porta, dos cunhais e das padieiras são alguns dos aspectos técnicos e construtivos que merecem especial destaque, tendo em conta que podem influenciar de forma decisiva o comportamento estrutural deste elemento construtivo. Deste modo, pretende-se contribuir para o conhecimento deste tipo de construção, e disponibilizar informação base que possa suportar estudos futuros de modelação numérica e/ou ensaios experimentais do comportamento de paredes em alvenaria de pedra de xisto.

In general, timber pavements are the main horizontal structural elements of the Portuguese traditional buildings. Since these types of buildings required to be preserved, the maintenance of timber pavements is crucial. However and unfortunately, the demolition of the interior of traditional buildings still is a current building option in rehabilitation processes. This building scenario is more expressive in private estate, in particular, in private dwellings. This option may be due to the lack of technical knowledge concerning timber pavements. Therefore, this paper intends to give a contribution in this matter by proposing an expedite methodology able to assess the structural vulnerability of these types of horizontal structural elements. Mapping the different structural vulnerability degrees of a traditional timber pavement may give guidance for maintenance, inspection and/or reinforcement design processes.

Punching shear failure on flat reinforced concrete slabs of residential and commercial buildings is generally avoided by using transversal reinforcement and/or chapiters. The first option requires intense labour, mainly when densely flexural reinforcement exists in the potential punching failure region, with detrimental consequences in terms of costs of this construction solution. The second option has also extra costs due to the necessity of special arrangements of moulds for casting the chapiters. The interference of a chapiter on the flatness of the slab can also be a negative aspect from the architectonic point of view. The use of steel fibre reinforcement can be a solution to avoid both the conventional punching reinforcement and chapiters. Therefore, an experimental program was carried out to assess the potentialities of steel fibre reinforced self-compacting concrete (SFRSCC) for the punching resistance of flat slabs centrically loaded. This experimental program is described, and the main results are presented and analysed. To assess the potentialities of the Reissner-Mindlin FEM-based theory for modelling the behaviour of flat SFRSCC slabs submitted to punching loading configuration, new features were introduced in the out-ofplane shear constitutive law of the SFRSCC. These features are briefly described and the main focus was given on the modelling strategy adopted for simulating the punching tests., Fundação para a Ciência e a Tecnologia (FCT)

In general, timber pavements are the main horizontal structural elements of the Portuguese traditional buildings. Since these types of buildings required to be preserved, the maintenance of timber pavements is crucial. However and unfortunately, the demolition of the interior of traditional buildings still is a current building option in rehabilitation processes. This building scenario is more expressive in private estate, in particular, in private dwellings. This option may be due to the lack of technical knowledge concerning timber pavements. Therefore, this paper intends to give a contribution in this matter by proposing an expedite methodology able to assess the structural vulnerability of these types of horizontal structural elements. Mapping the different structural vulnerability degrees of a traditional timber pavement may give guidance for maintenance, inspection and/or reinforcement design processes.

Os edifícios tradicionais portugueses apresentam especificidades técnicas locais. O clima e os materiais de construção disponíveis localmente são fatores condicionantes dessas especificidades. Por exemplo, os edifícios tradicionais algarvios, as açoteias, têm a cobertura em terraço e são pintados de branco. Por sua vez, os edifícios de xisto e de tabique do Alto Douro têm a cobertura inclinada com beirais e vãos de pequenas dimensões. Os edifícios de granito e de tabique das regiões de Trás-os-Montes e do Minho também têm coberturas inclinadas com beirais. Contudo, com o fenómeno da globalização, tem havido uma tendência de uniformização dos padrões construtivos e as especificidades locais parecem ter vindo a ser negligenciadas. O aparecimento de problemas ambientais resultantes, em grande parte, da emissão de gases de efeito de estufa para a atmosfera provenientes do aumento do consumo energético nos edifícios implica a adoção de medidas conducentes à redução desse consumo. Pensa-se que o conhecimento das características técnicas dos edifícios tradicionais de cada região poderá contribuir para minimizar este consumo e tornar assim os edifícios novos ou os edifícios a reabilitar mais eficientes energeticamente e, implicitamente, mais sustentáveis. Neste sentido, foi desenvolvida uma metodologia experimental, para avaliar o coeficiente de transmissão térmica de elementos construtivos de edifícios, passível de ser aplicada “in situ” e em laboratório. Esta metodologia permite uma monitorização contínua desse desempenho térmico durante vários dias e em condições termo higrométricas reais. Nesta comunicação serão apresentados alguns dos resultados obtidos através da aplicação desta metodologia a elementos construtivos e materiais existentes nos edifícios tradicionais da região de Trás-os-Montes e Alto Douro.

In general, this paper is focused on studding the ancient traditional schist buildings of the Alto Douro Wine Region, in the northeast of Portugal. In particular, it is devoted to evaluate the thermal performance of this type of buildings. Having accurate data related to this technical aspect is extremely relevant to perform an adequate future rehabilitation process. In fact, considering that the Alto Douro Wine Region is a relevant heritage, in which this type of buildings is an important part, to take preservation actions is crucial. Therefore, at this stage, ten ancient schist buildings were studied in terms of materials and construction details. The thermal behavior of a schist wall, with a thickness of 0,62 m, of one of these buildings was tested “in situ”, using a heat flux meter transfer system during ten consecutive days. The results obtained show that the thermal transmission coefficient of the schist wall is 1,114 W/m2oC. This value is lower than the one presented in the literature review and lower than the value obtained for other construction solutions. The study of the thermal behavior of the schist wall is important, in order to help future rehabilitation processes of this type of buildings. Further research work is required in order to test the results obtained in the work developed so far.

The benefits of adding fibres to concrete lie, mostly, in improving the post-cracking behaviour, since its ability to transfer stresses across cracked sections is substantially increased. The post-cracking strength is dependent not only on the fibre geometry, mechanical performance and fibre/matrix interface properties, but also on the fibre orientation and distribution. Previous works have shown that in self-compacting concrete matrices, there is a preferential fibre alignment according to the concrete’s flow in the fresh state. Having in mind that fibres are more efficient if they are oriented according the principal tensile stresses, a preferential fibre alignment on a certain direction could either enhance or diminish the material and the structural performance of this composite. In this paper, it is investigated the influence of the fibre orientation and distribution on the post-cracking behaviour of the steel fibre reinforced self-compacting concrete (SFRSCC). To perform this evaluation, SFRSCC panels were casted from their centre point. Two self-compacting mixtures were prepared using the same base mix proportions. For each SFRSCC panel cylindrical specimens were extracted and the post-cracking behaviour was assessed from a crack width controlled splitting tensile test.

In this work are presented and discussed the numerical simulations carried out for indirect tensile tests of steel fibre reinforced self-compacting concrete specimens. The post-cracking behaviour was modelled with two distinct approaches. Within the scope of the first one, the s-w relationships were obtained by an inverse analysis procedure up to distinct ultimate crack widths. The other approach consisted on modelling the behaviour of the composite based upon the micro-mechanical behaviour of the fibres. For this purpose the composite was modelled as two-phase material under the FEM basis, with an unreinforced concrete matrix phase (paste + aggregates) and a fibre phase. The fibre phase comprises information about fibre density and orientation depending on where and how the material is applied.

No presente trabalho irão ser descritas algumas soluções para a consolidação e/ou reforço de elementos estruturais de madeira utilizando diferentes técnicas, em função dos materiais utilizados: betão armado e elementos metálicos. Irão ser analisadas a possibilidade de introduzir elementos em betão armado e elementos/perfis metálicos, no reforço de elementos solicitados principalmente em flexão. Serão também analisadas as possibilidades de reforço e/ou consolidação de pilares e coberturas. Deste modo, serão descritas algumas soluções que permitirão aumentar a capacidade portante dos elementos ou do conjunto, sugerindo formas práticas de executar convenientemente algumas destas propostas. Com o desenvolvimento tecnológico ao nível dos materiais e das técnicas de produção e execução, o processo de reabilitação e recuperação dos pavimentos de madeira ganhou novo fôlego com a introdução de perfis metálicos e elementos de betão armado., The present work will describe some solutions for the consolidation and/or reinforcement of structural timber elements using different techniques taking into account the reinforcement materials used: concrete and steel. Will be also analyzed the possibility of introducing reinforced concrete and steel elements in the retrofitting of in bending wooden structures or elements. Finally, the possibilities of strengthening and/or consolidation of wooden columns and wooden roofs will be studied. Some solutions that increase the load bearing capacity of elements or structures will be described, and some practical issues will be presented. With the most recent technological development in materials and production techniques, the global process of rehabilitation and restoration of wooden floors gave new opportunities to the introduction of steel and reinforced concrete elements as a true solution.

Traditional buildings basically include natural and autochthonous construction materials and are built with sustainable construction techniques. The knowledge of these materials’s state and construction techniques is required for a proper conservation/renovation work. It is well known that the lack of maintenance is one of the main causes that contribute to the high degree of degradation that the Portuguese traditional buildings unfortunately have. That degradation may even compromise the overall structural integrity of the building thus reducing its lifetime`s expectation. Meanwhile, a partial or even full demolition of a building is still an often occurrence in the Portuguese context. From a sustainable and building heritage perspectives that practise may be inadequate. Taking into account that generally the degradation problems are linked with roof`s leaking anomalies and that the structural components of the roof tend to be the first ones to be affected, this timber structural roof components of Portuguese dwellings were the object of the research work here presented.

texto completo: acesso restrito. p. 9653–9658. Submitted by Ana Valéria de Jesus Moura (anavaleria_131@hotmail.com) on 2012-02-25T15:13:53Z No. of bitstreams: 1 nps70.tmp.pdf: 136822 bytes, checksum: b2b15cdfd1cd8a7b3109915462010189 (MD5) Made available in DSpace on 2012-02-25T15:13:53Z (GMT). No. of bitstreams: 1 nps70.tmp.pdf: 136822 bytes, checksum: b2b15cdfd1cd8a7b3109915462010189 (MD5) Previous issue date: 2011 This work aims to demonstrate the enzymatic production of fatty acid ethyl ester biodiesel from highly acidic feedstock in a single-step reaction, without co-solvents and avoiding the inhibition of the enzyme by ethanol and glycerol. Additionally, an empirical equation is proposed to predict the kinetics of the production reaction as a function of the used feedstock and catalyst concentration. Biodiesel production from highly acidic feedstock perform via simultaneous esterification of free fatty acids and transesterification of triacylglycerols. Enzymatic catalysis is one of the most promising alternative technologies for the biodiesel production. Increasing of the enzymatic bioactivity is crucial for the success of such process in industrial scale. Currently, stepwise addition of the alcohol or the use of co-solvents have been proposed to avoid enzyme inhibition, such strategies add downstream processes to the production. These results can be applied to the development economical-viable enzymatic production of biodiesel in industrial scale.

O betão auto-compactável reforçado com fibras de aço, BACRFA, combina os benefícios da tecnologia do betão auto-compactável com os inerentes à adição de fibras de aço a um material frágil de matriz cimentícia. Devido às especificidades intrínsecas à tecnologia do betão auto-compactável, os diversos mecanismos de reforço provenientes da mobilização das fibras diferem ligeiramente dos observados num betão convencional reforçado com fibras de aço, BRFA, repercutindo-se desta forma, em diferenças ao nível das propriedades mecânicas destes materiais compósitos. Actualmente, mesmo os BRFA ainda são relativamente pouco utilizados em aplicações estruturais, isto se tivermos em mente, que o aparecimento deste material compósito data do inicio dos anos 60. Um dos aspectos que contribui para esta reduzida utilização é a elevada dispersão observada no comportamento mecânico de BRFA, em parte devida a uma distribuição não uniforme das fibras na matriz. O BACRFA permite quer uma distribuição das fibras mais uniforme, quer uma orientação mais efectiva segundo a direcção do escoamento de betonagem, num provete ou elemento estrutural. Presentemente, é reconhecido que o BACRFA exibe um melhor comportamento pós-fendilhado, com uma menor variabilidade, comparativamente ao comportamento do BRFA. No presente artigo é apresentado o comportamento mecânico quer em tracção uniaxial, quer em flexão de BACRFA. Com este intuito foi realizado um programa experimental constituído por duas séries com diferentes percentagens volumétricas de fibras, uma com 0,38% e outra com 0,57%. Os principais resultados obtidos nos ensaios de tracção uniaxial e flexão são apresentados e discutidos.

Tese de Doutoramento em Engenharia Civil, The use of steel fibre reinforced self-compacting concrete, SFRSCC, probably, will swiftly increase in the next years, since this composite material introduces several advantages on the concrete technology. In fact, the partial or total replacement of the conventional bar reinforcement by discrete fibres optimizes the construction process. The assembly of the reinforcement bars in the construction of concrete structures has a significant economical impact on the final cost of this type of constructions, due to the man-labour time consuming that it requires. In the modern societies, the cost of the man-labour is significant, from which diminishing the man-labour will decrease the overall cost of the construction. In the fresh state, SFRSCC homogeneously spreads due to its own weight, without any additional compaction energy. Driven by its own weight, the concrete has to fill a mould completely without leaving entrapped air even in the presence of dense steel bar reinforcement. For these reasons, SFRSCC is a very promising construction material with a high potential of application, mainly in the cases where fibres can replace the conventional reinforcement. At the present time, however, the SFRSCC technology is not yet fully developed and controlled, and, much less, the mechanical behaviour of the SFRSCC material. The present work has been carried out involving experimental, analytical and numerical research. The main purpose was to achieve, as much as possible, a consistent comprehension of the behaviour of this composite material, and to collect data for the calibration of the analytical formulations and FEM-based numerical models. The experimental research covers aspects from distinct scale levels. At a micro-level, the micromechanics aspects of fibre reinforcement are ascertained. Passing through a meso-level, where the fibre distribution structure on the hardened concrete is assessed. The research carried out at a micro/meso level enables to have a deeper understanding of the multiple reinforcement mechanisms and factors which influences the overall composite behaviour at a macro-level. Finally, at macro-level, the composite mechanical behaviour, respectively, compressive, flexural and uniaxial tensile behaviour is assessed. The gathered experimental information at the distinct studied scale levels enables to acquire a deeper knowledge of the multiple reinforcement mechanisms involved. Thus, leading to the main goal of creating an integrated numerical approach, that from a rational and sustainable point of view, is able of predicting the mechanical properties of fibre reinforced composites, based on the fibres' micromechanical properties., A utilização de betão auto-compactável reforçado com fibras de aço, BACRFA, provavelmente, aumentará significativamente no decurso dos próximos tempos, visto que este material compósito introduz vários melhoramentos ao nível dos processos tecnológicos do betão. Na verdade, a substituição total ou parcial das armaduras convencionais, usadas no betão armado corrente, por fibras discretas de aço, contribui para optimização do processo construtivo. Para além dos benefícios tecnológicos, advém vantagens económicas devido a redução na duração do tempo de construção, nomeadamente, na montagem de armaduras convencionais. Nas sociedades modernas, em que a competitividade na indústria da construção se apresenta cada vez mais feroz, bem como com o aumento constante do preço da mão-de-obra, este material apresenta-se cada vez mais como uma solução premente. Contudo, presentemente, a tecnologia afecta ao BACRFA não esta ainda totalmente potenciada, assim como as suas propriedades mecânicas ainda não totalmente conhecidas. O presente trabalho desenvolvido na área dos BACRFA abrangeu investigação experimental, analítica e numérica. O principal propósito consistiu, quanto o possível, num exaustivo e consistente estudo das propriedades mecânicas deste material compósito, assim como no desígnio da obtenção de dados para a calibração de modelos analíticos e modelos numéricos suportados na formulação dos elementos finitos. A investigação experimental engloba o estudo do comportamento a diferentes escalas. A um nível micro, os principais mecanismos de reforço das fibras foram estudados e analisados. Passando para uma escala meso, foi dada especial atenção à distribuição das fibras numa matriz endurecida de BACRFA. A investigação do material a uma escala micro/meso permite o melhor conhecimento dos múltiplos mecanismos de reforço que influenciam o comportamento global do material compósito a um nível macro. Finalmente, a um nível macro, o comportamento do material compósito foi aferido para diversos tipos de carregamentos, respectivamente, tracção e compressão uniaxial assim como flexão. A informação recolhida a diferentes escalas, permitiu um melhor e profuso conhecimento sobre os múltiplos mecanismos de reforço envolvidos no BACRFA. Consequentemente, possibilitou a criação de uma estratégia numérica integrada, que de um ponto de vista racional e sustentável, facilita a previsão das propriedades mecânicas dos BACRFA baseada nas propriedades micro-mecânicas das fibras., Fundação para a Ciência e a Tecnologia (FCT)

In the present work the tensile behavior of a self-compacting concrete reinforced with two hooked ends steel fiber contents was assessed performing stable displacement control tension tests. Based on the stressdisplacement curves obtained, the stress-crack width relationships were derived, as well as the energy dissipated up to distinct crack width limits and residual strengths. The number of effective fibers bridging the fracture surface was determined and was compared with the theoretical number of fibers, as well as with the stress at crack initiation, residual stresses and energy dissipation parameters. In general, a linear trend between the number of effective fibers and both the stress and energy dissipation parameters was obtained. A numerical model supported on the finite element method was developed. In this model, the fiber reinforced concrete is assumed as a two phase material: plain concrete and fibers randomly distributed. The plain concrete phase was modeled with 3D solid finite elements, while the fiber phase was modeled with discrete embedded elements. The adopted interface behavior for the discrete elements was obtained from single fiber pullout tests. The numerical simulation of the uniaxial tension tests showed a good agreement with the experimental results. Thus, this approach is able of capturing the essential aspects of the fiber reinforced composite’s complex behavior., (undefined)

In reinforced concrete structures, it is extremely difficult to ensure that steel bars will be not subject, either in a lower or higher extent, to the corrosion effect. The application of hot dip galvanized rebar is an economic and effective way of protecting reinforced concrete against corrosion. This protective technique has an influence, which should not be disregarded, on the performance of the rebar’s coating, its behaviour and, fundamentally, the bond between concrete and galvanized rebar. With the aim of studying the bond behaviour between galvanized steel rebar and concrete, an experimental program was carried out by means of direct pullout tests. To predict the full pullout response, an analytical cohesive interface model was developed to obtain the bond stressslip relationship. To account for the interfacial bond, a nonlinear bond stress-slip law was used. In the present work the numerical method and mathematical tools are detailed and its performance is assessed. Hence, the parameters that define the local bond stress slip relationship are obtained by a fitting procedure between the simulated pullout curve and the experimental one. Finally, the obtained local bond law relationship is compared to the one proposed by the CEB-FIP Model Code.

A eficiência de uma fibra como meio de transferência de tensões é frequentemente determinada por intermédio de ensaios de arrancamento, sendo o deslizamento da fibra monitorizado em função da força de arrancamento aplicada na fibra. Nas últimas três décadas, vários fabricantes introduziram no mercado fibras com geometria melhorada, reivindicando melhores desempenhos comparativamente com as fibras lisas. Hoje em dia as fibras adicionadas a uma matriz cimentícia possuem, em geral, uma ancoragem mecânica. Recorrentemente, as fibras são produzidas por deformação mecânica das suas extremidades em forma de ganchos, cones, remos, etc. Não obstante, devido a diferentes materiais e processos de fabrico, as propriedades mecânicas das fibras como, a resistência à tracção, a eficiência da ancoragem mecânica diferem entre os vários fabricantes, mesmo considerando o mesmo tipo de fibra. Estas diferenças têm influência no comportamento ao arrancamento de uma fibra e, consequentemente, no comportamento mecânico de um material compósito reforçado com fibras. No presente trabalho é realizada uma análise comparativa de três tipos de fibras de aço com ancoragens em forma de gancho produzidas por três fabricantes distintos. A influência da variação das dimensões da geometria das fibras e das propriedades mecânicas destas no comportamento ao arrancamento foi avaliada. Ensaios à tracção e de arrancamento com fibras dos distintos fabricantes são apresentados, sendo analisados os resultados obtidos.

The effectiveness of a given fibre as a medium of stress transfer is often assessed using a single fibre pullout test, where fibre slip is monitored as a function of the applied load to the fibre. Over the past 30 years, so-called improved shaped fibres have been brought onto the market by different producers with claimed better performances than straight fibres. Nowadays, the most commonly used fibres have anchorage mechanisms. Generally, these fibres are produced by mechanically deforming the fibre with a hook, cone or paddle adjacent to each of its ends. Nevertheless, due to different materials and manufacturing processes, the mechanical properties such as, tensile strength and grade of mechanical anchorage differ amongst different producers, even for the same fibre type. These differences have an effect on the fibre pullout behaviour and, consequently, in the overall behaviour of FRC under loading. In the present work, a comparative study of three hook-ends fibres from different producers is carried out. The statistical variation of the fibre geometry dimensions is assessed, and its influence on the fibre mechanical properties is ascertained. Experimental tensile and pullout tests results of each fibre brand are presented and discussed.