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Avaliação do comportamento estrutural de pré-lajes de betão com fibras sintéticas
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Abstract(s)
O betão é um dos materiais mais utilizados na indústria da construção. Pode combinar-se com outros materiais (como o aço) para compensar algumas das suas características menos vantajosas, como a sua reduzia resistência à tração e o comportamento pouco dúctil. Nas últimas décadas, tem-se assistido ao desenvolvimento de betões com incorporação de diferentes tipos de fibras, melhorando algumas dessas desvantagens e possibilitando a redução ou eliminação das armaduras convencionais.
Neste contexto, apresenta-se nesta dissertação um estudo experimental para avaliar a possibilidade de utilizar pré-lajes constituídas por betão com adição de fibras sintéticas como cofragens perdidas para a betonagem da laje de tabuleiro de uma ponte a construir em ambiente marítimo. Primeiramente determinaram-se as propriedades mecânicas de betão simples (como referência) e de betão com duas dosagens de fibras de poliolefinas (6 kg/m3 e 10 kg/m3). De seguida, foram realizados ensaios de flexão em pré-lajes constituídas pelos 3 tipos de betão com dimensões 100 × 50 × 5 cm3 definidos a partir do caso de estudo, sujeitas a diferentes tipos de carregamento e condições de apoio, que, além de tentarem simular aproximadamente as ações a que serão sujeitas no caso de estudo, pretenderam simular outras possíveis aplicações.
Os resultados obtidos nos ensaios mostraram um aumento da carga máxima e da resistência residual pós-fissuração com o aumento da dosagem de fibras. Observou-se ainda que nas pré-lajes de betão com fibras foi possível atingir níveis de ductilidade consideráveis. Finalmente, concluiu-se que as pré-lajes estudadas apresentam uma resistência suficiente para suportar as ações impostas durante a fase de betonagem da laje do tabuleiro da ponte.
Concrete is one of the most widely used materials in the construction industry. It can be combined with other materials (such as steel) to compensate for some of its less advantageous characteristics, such as its low tensile strength and low ductile behaviour. The last few decades have seen the development of concrete incorporating different types of fibres, improving some of these disadvantages and making it possible to reduce or eliminate conventional reinforcement. In this context, this dissertation presents an experimental study to assess the possibility of using pre-slabs made of concrete with added synthetic fibres as lost formwork for a concrete bridge deck to be built in a maritime environment. Firstly, the mechanical properties of plain concrete (as a reference) and concrete with two dosages of polyolefins fibres (6 kg/m3 and 10 kg/m3) were determined. Next, flexural tests were carried out on pre-slabs made of the 3 types of concrete with dimensions of 100 × 50 × 5 cm3 defined from the case study, subjected to different types of loading and support conditions which, in addition to trying to approximately simulate the actions to which they will be subjected in the case study, were intended to simulate other possible applications. The results obtained in the tests showed an increase in the maximum load and post-cracking residual strength as the fibre dosage increased. It was also observed that it was possible to achieve considerable levels of ductility in concrete pre-slabs with fibres. Finally, it was concluded that the pre-slabs studied have sufficient strength to withstand the actions imposed during the casting phase of the concrete bridge deck.
Concrete is one of the most widely used materials in the construction industry. It can be combined with other materials (such as steel) to compensate for some of its less advantageous characteristics, such as its low tensile strength and low ductile behaviour. The last few decades have seen the development of concrete incorporating different types of fibres, improving some of these disadvantages and making it possible to reduce or eliminate conventional reinforcement. In this context, this dissertation presents an experimental study to assess the possibility of using pre-slabs made of concrete with added synthetic fibres as lost formwork for a concrete bridge deck to be built in a maritime environment. Firstly, the mechanical properties of plain concrete (as a reference) and concrete with two dosages of polyolefins fibres (6 kg/m3 and 10 kg/m3) were determined. Next, flexural tests were carried out on pre-slabs made of the 3 types of concrete with dimensions of 100 × 50 × 5 cm3 defined from the case study, subjected to different types of loading and support conditions which, in addition to trying to approximately simulate the actions to which they will be subjected in the case study, were intended to simulate other possible applications. The results obtained in the tests showed an increase in the maximum load and post-cracking residual strength as the fibre dosage increased. It was also observed that it was possible to achieve considerable levels of ductility in concrete pre-slabs with fibres. Finally, it was concluded that the pre-slabs studied have sufficient strength to withstand the actions imposed during the casting phase of the concrete bridge deck.
Description
Keywords
Betão reforçado com fibras propriedades mecânicas pré-lajes ensaios de flexão Fibre-reinforced concrete mechanical properties pre-slabs flexural tests