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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Análise da resistência residual de compressão de blocos, prismas e pequenas paredes de alvenaria estrutural de blocos de concreto submetidos à situação de incêndio / Residual compressive strength of blocks, prisms and walls of concrete structural masonry under fire situation.

Dupim, Rafael Henrique 03 June 2019 (has links)
Alvenaria estrutural é um sistema construtivo em que paredes exercem tanto função estrutural como de vedação. Apesar de ser largamente utilizada no Brasil atualmente, não há uma norma nacional com procedimentos para o dimensionamento deste sistema em situação de incêndio. Muito se deve pelo fato de as pesquisas nesta área serem substancialmente escassas se comparadas com os sistemas construtivos em concreto armado ou aço. Neste contexto, este trabalho tem por objetivo realizar ensaios experimentais para avaliar a resistência residual de compressão da alvenaria estrutural com blocos de concreto. Foram avaliadas duas variações de blocos de concreto, com resistências características de 4,0 e de 10,0 MPa, ambos com espessura nominal de 140 mm e os corpos de prova estudados foram os prismas e as pequenas paredes. Realizou-se a caracterização física, geométrica e mecânica da alvenaria em temperatura ambiente e na sequência os corpos de prova foram submetidos a uma simulação de incêndio-padrão normalizado pela ISO 834-1:1999, durante 120 minutos que é o TRRF máximo recomendado pela ABNT NBR 14432:2001. Na primeira fornada foram avaliados os elementos de 140 mm sem revestimento e segunda fornada todos os elementos revestidos com uma camada de 5 mm de gesso. Após o resfriamento lento até a temperatura ambiente, os corpos de prova foram submetidos ao ensaio de compressão simples para avaliar a resistência residual de compressão dos blocos, prismas e pequenas paredes. Em todos os casos as resistências encontradas ficaram abaixo do suficiente para garantir a segurança durante a ação de um incêndio, uma vez que o máximo de resistência residual encontrado foi de 22%. A influência da compartimentação na resistência residual das pequenas paredes, foi brevemente avaliada, para isso três pequenas paredes de 4,0 MPa e 140 mm com o interior isolado dos gases externos foram submetidas ao incêndio-padrão e compressão pós resfriamento, verificou-se que a perda de resistência neste caso foi de 54% enquanto nas pequenas paredes com fogo em todas as faces e expostas ao fogo pelo mesmo período a perda foi de 86%. Estas pequenas paredes compartimentadas foram instrumentadas com a finalidade de avaliar a transferência de calor ao longo da sessão transversal e verificar o tempo de atendimento do critério de isolamento, que neste caso foi de 62 minutos, abaixo do TRRF máximo de 120 minutos. / Structural masonry is a building system that walls work as structure and has sealing function too. Even though it is widely used in Brazil nowadays, there is no national standardization for the masonry design in fire situation. One of the reasons is that researches in this area are substantially sparse if compared with other building systems like reinforced concrete and steel. In this context, the purpose of this work is to evaluate the residual compressive strength of concrete structural masonry by experimentally tests. Two concrete block variations were evaluated, with strengths of 4,0 and 10,0 MPa, both with 140 mm nominal thickness, the elements studied were prisms and walls, beyond blocks. In the first stage, the masonry was characterized in ambient temperature and in the second stage, the elements were submitted to fire simulation standardized by ISO 834-1: 1999 for 120 minutes, which is the maximum TRRF recommended by ABNT NBR 14432: 2001. In the first fire simulation the 140 mm elements were evaluated without covering and in the second one, all the elements were covered with 5 mm layer of plaster. Then, after slow cooling until ambient temperature, the residual compressive strength of the blocks, prisms and walls was evaluated by compression test. In all cases the resistances were not enough to ensure safety during the fire, since the maximum residual resistance found was 22%. Still in this stage, the influence of the compartmentation on the residual resistance of the walls was briefly evaluated. Three walls of 4.0 MPa and 140 mm were placed in a triangle that was thermally insulated inside, and after the fire simulation were subjected in a post-cooling compression test. The loss of resistance found in this case was 54% while in the walls with fire on all faces and exposed to fire for the same period the loss was 86%. These compartmentalized walls were instrumented with the purpose of evaluating the heat transfer along the cross section and to check the time of the isolation criterion attendance, which in this case was 62 minutes, below the 120-minute established as maximum TRRF.
32

Comportamento em altas temperaturas e na reidratação de concretos convencional e com cinza de casca de arroz

Almeida, Jacinto Manuel Antunes de January 2017 (has links)
O refinamento dos poros, associado à reação pozolânica e ao efeito filer, reduz a permeabilidade do concreto com cinza de casca de arroz (CCA), o que pode antecipar a sua degradação em altas temperaturas. A literatura mostra que o concreto reidratado em água pode recuperar substancialmente a sua resistência inicial, porém, os estudos sobre a reidratação ao ar e sobre a influência do modo de resfriamento na reidratação são escassos. A pesquisa desenvolvida teve como principal objetivo avançar na análise experimental de concretos convencional e com CCA em altas temperaturas e na reidratação. Na etapa exploratória se avaliou a influência da temperatura de exposição, da adição mineral, do ambiente de acondicionamento, da taxa de aquecimento e do tempo de exposição na resistência à compressão e módulo de elasticidade. Na etapa principal se avaliou a influência do modo de resfriamento, da adição e da idade de reidratação na resistência residual. Complementarmente se utilizou o ensaio de velocidade de pulso ultrassônico (VPU) para avaliar o grau de microfissuração e correlacionar a VPU com as propriedades mecânicas residuais. Na etapa exploratória concluiu-se que a adição, a temperatura, a taxa de aquecimento e o tempo de exposição influenciaram significativamente os resultados. O concreto com CCA cristalina apresentou pior desempenho em altas temperaturas. O concreto com CCA amorfa apresentou desempenho ligeiramente inferior ao concreto convencional em 200°C, devido ao efeito da poro-pressão. No entanto, ambas as CCA podem ser alternativas viáveis considerando sustentabilidade. Na etapa principal, o resfriamento brusco com água provocou maior redução na resistência devido aos gradientes térmicos, porém, permitiu maior recuperação logo nos primeiros sete dias de reidratação. Apesar da recuperação parcial, a resistência ao fim de 154 dias foi inferior a 40% do valor inicial. Nas análises térmicas e de DRX foi possível observar nos concretos resfriados com água a recristalização dos aluminatos de cálcio, do C-S-H e da portlandita, em maior grau no concreto convencional. Foi possível observar correlações fortes entre as variáveis de resposta na etapa exploratória, porém, o mesmo não ocorreu na etapa principal, devido à fissuração e presença de água nos poros. / The pore refinement, associated with the pozzolanic reaction and the filler effect, reduces the permeability of blended concrete with rice husk ash (RHA), which can anticipate its degradation at high temperatures. The literature shows that concrete rehydrated with water can recover substantially its initial strength, but studies on rehydration in air and on the influence of the cooling method on rehydration are scarce. The main objective of this research was to evaluate the performance at high temperatures and in rehydration of conventional and blended concretes with RHA. In the exploratory stage, the influence of exposure temperature, mineral admixture, conditioning environment, heating rate and exposure time on residual strength and modulus of elasticity of heated concrete was evaluated. In the main stage, the influence of cooling method, mineral admixture and time of rehydration in an unsaturated environment on residual strength of concrete was evaluated. The ultrasonic pulse velocity test (UPV) was used to evaluate the degree of micro cracking of concrete and to correlate the UPV with residual strength and modulus. In the exploratory stage it was concluded that mineral admixture, temperature, heating rate and time of exposure significantly influenced the results. In general, concrete with partially crystalline RHA presented the worst performance at high temperatures. Concrete with amorphous RHA presented worse performance than conventional concrete only at 200°C, due to the pore-pressure effect. Despite these results, RHA can be a viable option considering sustainability and high temperatures performance. In the main stage, the rapid cooling with water caused a greater reduction in strength, due to thermal gradients, however, caused a greater strength recovery in the first seven days of rehydration. Despite this partial recovery, the final strength of both concretes after 154 days of rehydration was less than 40% of the initial value. In water-cooled concretes thermal and XRD analyzes show recrystallization of the calcium aluminates, C-S-H and portlandite, to a greater degree in conventional concrete. In the exploratory stage it was possible to observe strong correlations between the independent variables; however, the same did not occur in the main stage, due to cracking and to the presence of water in the pores.
33

海洋環境において腐食した鋼管の形状計測と残存耐力に関する検討

田村, 功, Tamura, Isao, 渡邊, 英一, Watanabe, Eiichi, 伊藤, 義人, Itoh, Yoshito, 藤井, 堅, Fujii, katashi, 野上, 邦栄, Nogami, Kuniei, 杉浦, 邦征, Sugiura, kunitomo, 永田, 和寿, Nagata, kazutoshi, 岡, 扶樹, Oka, Tomoki 03 1900 (has links)
No description available.
34

Effet de la corrosion sur les propriétés mécaniques de l'armature corrodée et la performance structurale résiduelle des poutres corrodées / Effect of corrosion on the mechanical properties of the corroded reinforcement and the residual structural performance of the corroded beams

Zhu, Wenjun 13 March 2014 (has links)
Cette thèse s’intéresse à l’étude l’effet de la corrosion sur les propriétés mécaniques des armatures corrodées et les performances mécaniques résiduelles des poutres corrodées. L’étude est basée sur deux poutres corrodées notées B2CL2 et B2CL3, conservées respectivement 26 ans et 28 ans en ambiance saline. Deux poutres non corrodées B2T2 et B2T3 conservées en conditions ambiantes ont également été testés afin d’identifier l'effet de la corrosion indépendamment du vieillissement.Les propriétés mécaniques des armatures corrodées ont été étudiées par des essais de traction.La limite d'élasticité et résistance à la rupture ont été étudiées sur la base de la section transversale résiduelle évaluée par perte de masse. Les résultats ont montré que les effets de la corrosion sur la diminution ductilité étaient très importants. La forme de la section transversale résiduelle apparait comme étant un paramètre essentiel affectant la ductilité de l'armature.Les performances résiduelles en flexion des poutres corrodées ont été étudiées. Les résultats montrent que la corrosion réduit la capacité portante et de façon plus significative, la flèche maximale à rupture en raison d’un changement de mode de rupture. La diminution de la charge de plasticité apparait en relation avec la perte de section d’acier tendu due à la corrosion Des poutres de portées courtes ont été réalisées à partir des poutres corrodées après les essais de flexion. Les tests mécaniques ont été effectués en flexion pour vérifier la réponse des poutres courtes corrodées. Les poutres courtes corrodées ont péri en flexion avec une bonne ductilité tandis que les poutres courtes non corrodées ont péri comme prévu en cisaillement suivant un mode de rupture fragile, qui a montré que la corrosion de l'armature pouvait modifier les modes de défaillance.Les produits de corrosion ont été recueillis à partir de l'armature corrodée de B2Cl3. Des expériences XRD et TG ont été menées afin d'identifier la composition des produits de corrosion. Le coefficient d'expansion des produits de corrosion a été déduit, ce qui pourrait être utile pour les recherches futures concernant le mécanisme de fissuration du béton d'enrobage. / The thesis aims to study the influence of chloride corrosion on the mechanical properties ofthe reinforcement and RC beams. The experiments were based on two corroded beams named B2Cl2 and B2Cl3, with a corroded age of 26 years and 28 years respectively. Two noncorroded beams B2T2 and B2T3 which were cast in the same condition and same time were also tested in order to make clear the corrosion effect.The mechanical properties of the corroded reinforcement were investigated by the tensiontests. The yield strength and ultimate strength were studied based on the residual gravimetrical cross-section. The results found that the impact of corrosion on the ductility was more significant than that of the strength. The shape of residual cross-section was considered to be in deep relationships with the ductility of the reinforcement.The flexural performances of the beams were studied. The results showed that the corrosion deteriorated the capacity and the ductility of the corroded beams. The corrosion degree of reinforcement was found in linear with the residual yield capacity of the corroded beams.The short-span beams were formed from the corroded beams after bending tests. Mechanical tests were carried out directly to check the response of the corroded beams. The corroded short-span beams failed in bending mode with good ductility while the non-corroded beams performed a brittle shear failure mode, which showed that the corrosion of reinforcement could change the failure modes.The corrosion products were collected from the corroded reinforcement of B2Cl3. XRD andTG experiments were conducted so as to identify the composition of the corrosion products.The expansive coefficient of the corrosion products was deduced, which could be helpful forthe further research on the cracking mechanism of the concrete cover
35

Comportamento em altas temperaturas e na reidratação de concretos convencional e com cinza de casca de arroz

Almeida, Jacinto Manuel Antunes de January 2017 (has links)
O refinamento dos poros, associado à reação pozolânica e ao efeito filer, reduz a permeabilidade do concreto com cinza de casca de arroz (CCA), o que pode antecipar a sua degradação em altas temperaturas. A literatura mostra que o concreto reidratado em água pode recuperar substancialmente a sua resistência inicial, porém, os estudos sobre a reidratação ao ar e sobre a influência do modo de resfriamento na reidratação são escassos. A pesquisa desenvolvida teve como principal objetivo avançar na análise experimental de concretos convencional e com CCA em altas temperaturas e na reidratação. Na etapa exploratória se avaliou a influência da temperatura de exposição, da adição mineral, do ambiente de acondicionamento, da taxa de aquecimento e do tempo de exposição na resistência à compressão e módulo de elasticidade. Na etapa principal se avaliou a influência do modo de resfriamento, da adição e da idade de reidratação na resistência residual. Complementarmente se utilizou o ensaio de velocidade de pulso ultrassônico (VPU) para avaliar o grau de microfissuração e correlacionar a VPU com as propriedades mecânicas residuais. Na etapa exploratória concluiu-se que a adição, a temperatura, a taxa de aquecimento e o tempo de exposição influenciaram significativamente os resultados. O concreto com CCA cristalina apresentou pior desempenho em altas temperaturas. O concreto com CCA amorfa apresentou desempenho ligeiramente inferior ao concreto convencional em 200°C, devido ao efeito da poro-pressão. No entanto, ambas as CCA podem ser alternativas viáveis considerando sustentabilidade. Na etapa principal, o resfriamento brusco com água provocou maior redução na resistência devido aos gradientes térmicos, porém, permitiu maior recuperação logo nos primeiros sete dias de reidratação. Apesar da recuperação parcial, a resistência ao fim de 154 dias foi inferior a 40% do valor inicial. Nas análises térmicas e de DRX foi possível observar nos concretos resfriados com água a recristalização dos aluminatos de cálcio, do C-S-H e da portlandita, em maior grau no concreto convencional. Foi possível observar correlações fortes entre as variáveis de resposta na etapa exploratória, porém, o mesmo não ocorreu na etapa principal, devido à fissuração e presença de água nos poros. / The pore refinement, associated with the pozzolanic reaction and the filler effect, reduces the permeability of blended concrete with rice husk ash (RHA), which can anticipate its degradation at high temperatures. The literature shows that concrete rehydrated with water can recover substantially its initial strength, but studies on rehydration in air and on the influence of the cooling method on rehydration are scarce. The main objective of this research was to evaluate the performance at high temperatures and in rehydration of conventional and blended concretes with RHA. In the exploratory stage, the influence of exposure temperature, mineral admixture, conditioning environment, heating rate and exposure time on residual strength and modulus of elasticity of heated concrete was evaluated. In the main stage, the influence of cooling method, mineral admixture and time of rehydration in an unsaturated environment on residual strength of concrete was evaluated. The ultrasonic pulse velocity test (UPV) was used to evaluate the degree of micro cracking of concrete and to correlate the UPV with residual strength and modulus. In the exploratory stage it was concluded that mineral admixture, temperature, heating rate and time of exposure significantly influenced the results. In general, concrete with partially crystalline RHA presented the worst performance at high temperatures. Concrete with amorphous RHA presented worse performance than conventional concrete only at 200°C, due to the pore-pressure effect. Despite these results, RHA can be a viable option considering sustainability and high temperatures performance. In the main stage, the rapid cooling with water caused a greater reduction in strength, due to thermal gradients, however, caused a greater strength recovery in the first seven days of rehydration. Despite this partial recovery, the final strength of both concretes after 154 days of rehydration was less than 40% of the initial value. In water-cooled concretes thermal and XRD analyzes show recrystallization of the calcium aluminates, C-S-H and portlandite, to a greater degree in conventional concrete. In the exploratory stage it was possible to observe strong correlations between the independent variables; however, the same did not occur in the main stage, due to cracking and to the presence of water in the pores.
36

Comportamento em altas temperaturas e na reidratação de concretos convencional e com cinza de casca de arroz

Almeida, Jacinto Manuel Antunes de January 2017 (has links)
O refinamento dos poros, associado à reação pozolânica e ao efeito filer, reduz a permeabilidade do concreto com cinza de casca de arroz (CCA), o que pode antecipar a sua degradação em altas temperaturas. A literatura mostra que o concreto reidratado em água pode recuperar substancialmente a sua resistência inicial, porém, os estudos sobre a reidratação ao ar e sobre a influência do modo de resfriamento na reidratação são escassos. A pesquisa desenvolvida teve como principal objetivo avançar na análise experimental de concretos convencional e com CCA em altas temperaturas e na reidratação. Na etapa exploratória se avaliou a influência da temperatura de exposição, da adição mineral, do ambiente de acondicionamento, da taxa de aquecimento e do tempo de exposição na resistência à compressão e módulo de elasticidade. Na etapa principal se avaliou a influência do modo de resfriamento, da adição e da idade de reidratação na resistência residual. Complementarmente se utilizou o ensaio de velocidade de pulso ultrassônico (VPU) para avaliar o grau de microfissuração e correlacionar a VPU com as propriedades mecânicas residuais. Na etapa exploratória concluiu-se que a adição, a temperatura, a taxa de aquecimento e o tempo de exposição influenciaram significativamente os resultados. O concreto com CCA cristalina apresentou pior desempenho em altas temperaturas. O concreto com CCA amorfa apresentou desempenho ligeiramente inferior ao concreto convencional em 200°C, devido ao efeito da poro-pressão. No entanto, ambas as CCA podem ser alternativas viáveis considerando sustentabilidade. Na etapa principal, o resfriamento brusco com água provocou maior redução na resistência devido aos gradientes térmicos, porém, permitiu maior recuperação logo nos primeiros sete dias de reidratação. Apesar da recuperação parcial, a resistência ao fim de 154 dias foi inferior a 40% do valor inicial. Nas análises térmicas e de DRX foi possível observar nos concretos resfriados com água a recristalização dos aluminatos de cálcio, do C-S-H e da portlandita, em maior grau no concreto convencional. Foi possível observar correlações fortes entre as variáveis de resposta na etapa exploratória, porém, o mesmo não ocorreu na etapa principal, devido à fissuração e presença de água nos poros. / The pore refinement, associated with the pozzolanic reaction and the filler effect, reduces the permeability of blended concrete with rice husk ash (RHA), which can anticipate its degradation at high temperatures. The literature shows that concrete rehydrated with water can recover substantially its initial strength, but studies on rehydration in air and on the influence of the cooling method on rehydration are scarce. The main objective of this research was to evaluate the performance at high temperatures and in rehydration of conventional and blended concretes with RHA. In the exploratory stage, the influence of exposure temperature, mineral admixture, conditioning environment, heating rate and exposure time on residual strength and modulus of elasticity of heated concrete was evaluated. In the main stage, the influence of cooling method, mineral admixture and time of rehydration in an unsaturated environment on residual strength of concrete was evaluated. The ultrasonic pulse velocity test (UPV) was used to evaluate the degree of micro cracking of concrete and to correlate the UPV with residual strength and modulus. In the exploratory stage it was concluded that mineral admixture, temperature, heating rate and time of exposure significantly influenced the results. In general, concrete with partially crystalline RHA presented the worst performance at high temperatures. Concrete with amorphous RHA presented worse performance than conventional concrete only at 200°C, due to the pore-pressure effect. Despite these results, RHA can be a viable option considering sustainability and high temperatures performance. In the main stage, the rapid cooling with water caused a greater reduction in strength, due to thermal gradients, however, caused a greater strength recovery in the first seven days of rehydration. Despite this partial recovery, the final strength of both concretes after 154 days of rehydration was less than 40% of the initial value. In water-cooled concretes thermal and XRD analyzes show recrystallization of the calcium aluminates, C-S-H and portlandite, to a greater degree in conventional concrete. In the exploratory stage it was possible to observe strong correlations between the independent variables; however, the same did not occur in the main stage, due to cracking and to the presence of water in the pores.
37

Analýza spoje křídlo-trup letounu L 410 NG z hlediska filozofie konstrukce s přípustným poškozením / Damage tolerance analysis of wing to fuselage joint of L 410 NG airplane

Duchoň, Peter January 2014 (has links)
Master's thesis deals with the damage tolerance analysis of wing-to-fuselage joint of L 410 NG airplane. Thesis includes determination of the load distribution to the individual attachments of wing-to-fuselage joint, residual strength analysis and residual fatigue life analysis of the most loaded attachment lugs, calculation of fatigue crack growth curves in the attachment solids and inspection program proposal. This analysis was performed using FE model of the wing and central part of the fuselage and AFGROW software.
38

Fließverhalten und Morphologieeinfluß granulierter spröder Materialien bei hohen Drücken und Belastungsgeschwindigkeiten

Schneider, Ines 01 February 2001 (has links)
Die Arbeit beschäftigt sich mit der Weiterentwicklung des verdämmten Druckversuches zur Bestimmung experimenteller Daten an verschiedenen Keramik- und Glassorten. Die untersuchten Materialien (Al2O3, TiB2, B4C, Floatglas, schweres Flintglas) lagen in Form von Fragmenten (Bruchstücken) vor und wurden aus realen Impaktexperimenten wiedergewonnen. Zusätzlich wurden thermisch vorgeschädigte Aluminiumoxidzylinder in die Betrachtungen einbezogen. Daten granulierter bzw. vorgeschädigter spröder Materialien sind von besonderem Interesse für Finite Element Rechnungen, um beispielsweise experimentell sehr aufwendige Beschußversuche rechnerisch zu simulieren.Als Untersuchungsmethode wurde der verdämmte Druckversuch verwendet und sowohl an quasistatische als auch an schlagdynamische Belastungsbedingungen angepaßt. Außerdem wurden die entwickelten Testaufbauten für sehr hohe hydrostatische Drücke optimiert. In den quasistatischen Experimenten konnten damit Drücke von 380 MPa bis 1960 MPa und in den dynamischen Versuchen von 495 MPa bis 2060 MPa erreicht werden. Im Ergebnis wurden mechanische Kennwerte der granulierten bzw. vorgeschädigten Materialien ermittelt (Restfestigkeit, Verdichtungsverhalten) und deren Schädigungsgrad vor und nach den Versuchen bestimmt (Rasterelektronenmikroskopie und Messung der spezifischen Oberfläche). Die vielversprechenden Resultate der verschiedenen Keramiken und Gläser wurden verglichen und die Materialien im Hinblick auf ihr Energieaufnahmevermögen unter schlagartiger Belastung bewertet.
39

Environmental and technical evaluation of cement reduction and test methods for fibre reinforced shotcrete in tunnels

Brodd, Elin, Östlund, Lina January 2022 (has links)
The dominating support method for hard rock tunnels today is use of fibre reinforced shotcrete in combination with rock bolts. The fibre reinforced shotcrete secures smaller blocks, while rock bolts are used to support larger blocks in the rock. Application of shotcrete is done by spraying against the rock surface using compressed air. The use of accelerators result in fast strength development and adhesive properties, which are two characteristics of great importance when constructing tunnels. This thesis aims at increasing the understanding of climate impact from fibre reinforced shotcrete in tunnel construction. The focus is on reducing the climate impact with two methods: reducing the share of cement in the shotcrete mixture through substitution with addition materials and using better test methods for fibres. Cement is one of the most important ingredients in concrete, however also the largest contributor to CO2 emissions. Reducing the cement amount is therefore a way of reducing the emissions of concrete. In addition, when testing the performance of fibres, different methods can lead to a spread in the results, causing an overuse of fibres in the shotcrete. First, the thesis investigated the use of alternative binder materials, especially Ground Granulated Blast Furnace Slag (GGBS), as a substitute for cement. Experimental testing was performed in a laboratory to evaluate the compressive strength for shotcrete with different amounts of GGBS. Testing was performed after one and seven days in order to evaluate the early strength. Second, the thesis investigated the use of fibre reinforcement and the possibilities of reducing the fibre dosage when changing fibre type and test method. Numerical modelling was performed for two test methods, beam and panel testing, based on experimental data. The thesis evaluated the environmental performance in terms of Global Warming Potential for both fibres and binder. The results show that substituting cement with GGBS has the largest potential to lower the CO2 emissions from fibre reinforced shotcrete. In addition, the fibre dosage can be lowered by changing fibre type, but also test method. Also this lowers the emissions, however the main emissions origins from the binder part. / Den dominerande förstärkningsmetoden för tunnlar i hårt berg idag är fiberarmerad sprutbetong i kombination med bergbultar. Den fiberarmerade sprutbetongen säkrar mindre block, medan bergbultar säkrar större block från att falla ner. Sprutbetongen appliceras genom sprutning direkt mot bergytan men hjälp av tryckluft. Användning av acceleratorer medför snabb hållfasthetsutveckling och vidhäftande egenskaper, vilka är av stor vikt vid tunnelkonstruktion. Syftet med examensarbetet är att öka förståelsen för klimatpåverkan från fiberarmerad sprutbetong i tunnelkonstruktion. Fokus är att undersöka minskningar i klimatpåverkan med två metoder: minska andelen cement i betongblandningen genom ersättning med alternativa material och använda bättre testmetoder för fibrer. Cement är en av de viktigaste ingredienserna i betong, men också den största bidragande faktorn till koldioxidutsläpp. Minskning av andelen cement är därför ett sätt att reducera utsläppen från betong. Dessutom kan valet av testmetod ha stor påverkan på vilken dosering av fibrer som krävs. Examensarbetet undersökte först användningen av alternativa bindemedelsmaterial, speciellt granulerad masugnsslagg, i sprutbetong som ett ersättningsmaterial till cement. Experiment i labb utfördes för att utvärdera tryckhållfastheten för gjuten sprutbetong med olika andelar granulerad masugnsslagg. Testning genomfördes efter en respektive sju dagar för att utvärdera hur slagg påverkar den tidiga hållfastheten. Användningen av fiberarmering och möjligheten att reducera fiberinnehållet vid byte av fibersort och testmetod undersöktes sedan. Numerisk modellering genomfördes för två testmetoder, balk- och plattest, baserat på experimentell data. Examensarbetet utvärderade klimatpåverkan i termer av Global Warming Potential, GWP, för både fibrer och bindemedel i sprutbetong. Resultaten visar att ersättning av cement med granulerad masugnsslagg har den största potentialen att minska koldioxidutsläppen från fiberarmerad sprutbetong. Dessutom kan fiberdoseringen minskas genom ändrad fibertyp samt ändrad testmetod, vilket också minskar utsläppen. Emellertid härstammar de största utsläppen från bindemedlet.
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Dano em materiais compósitos: SAFECom (Sistema de Análise de Fadiga de Estruturas em Compósito) / Damage in composite materials: SAFECom (System of Analysis of Fatigue for Composites)

Daniel, Giovani Sacchetto 09 December 2011 (has links)
O presente trabalho, inicialmente, apresenta uma revisão a cerca de vários métodos de análise de fadiga e tolerância ao dano em materiais compósitos e, em particular, o conceito de elemento crítico e o método da resistência residual é estudado e aplicado à análise de materiais compósitos poliméricos, reforçados por fibras contínuas, sob cargas cíclicas. Casos de laminados com concentradores de tensão são também abordados, principalmente, devido ao crescente emprego de materiais compósitos. Diante do contexto apresentado, o presente trabalho buscou desenvolver uma ferramenta computacional, que fosse capaz de prever de forma consistente tanto a vida em fadiga de estruturas em material compósito como a resistência residual dessas estruturas sob a ação de carregamentos cíclicos. Dessa forma, um modelo baseado na resistência residual, que envolve integração numérica, é implementado em um programa computacional denominado SAFECom (Sistema de Análise de Fadiga de Estruturas em Compósito), o qual é aplicado a alguns estudos de casos. O SAFECom foi, então, avaliado, comparando resultados obtidos com dados da literatura. Verifica-se uma boa convergência entre os resultados nessa fase de avaliação. Por fim, são listadas possibilidades de aprimoramento do programa, que podem torná-lo aplicável a outros estudos de casos não abordados no presente trabalho, além da avaliação do mesmo através de ensaios experimentais. / This work firstly presents an overview about various methods of analysis of fatigue and damage tolerance of composite materials and, in particular, the concept of critical element and the method of residual strength are studied and applied to the analysis of polymer composites reinforced by continuous fibers under cyclic loading. Cases of laminates with stress concentrators are also addressed, mainly due to increasing use of composite materials. In this context, this work aimed to develop a computational tool that was able to consistently predict both the fatigue life of structures in composite material and the residual strength of these structures under the action of cyclic loads. Thus, a model based on residual strength, which involves numerical integration, is implemented in a computer program called SAFECom (System of Analysis of Fatigue for Composites), which is applied to some case studies. The SAFECom is evaluated by comparing results obtained from literature data. There is a good convergence between the results of this assessment. Finally, possibilities for improvement are listed on the program that can make it applicable to other case studies, which were not covered in this study, in addition to its evaluation by experimental tests.

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