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The pressure of concrete on formwork in narrow sectionsClear, C. A. January 1986 (has links)
No description available.
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Water transport due to wick action through concreteAldred, James M. January 2008 (has links)
Wick action is the transport of water through a concrete element from a face in contact with water to a drying face as occurs in basements, tunnels, slabs on grade and hollow offshore structures. Water transport through concrete due to wick action is many times greater due to pressure permeability under typical environmental conditions. Therefore wick action plays an important role in the watertightness and durability of concrete structures. Current models of wick action are based on an equilibrium developing between the rate of water entering concrete by sorptivity and leaving by water vapour diffusion where initial moisture content should not change the steady state rate, only the dominant factor in the early stages. / Wick action tests were conducted on concrete specimens of varying initial moisture condition, thickness, orientation and composition over periods ranging up to 450 days. Some wick action tests were conducted at 50% and 75% relative humidity and using a penetrating solution of reduced surface tension. The rate of wick action was found to be inversely proportional to thickness regardless of the initial moisture content of the specimen. Initial saturation was found to significantly increase wick action and moisture flow in ordinary Portland cement (OPC) and hydrophobic (HI) concretes drying at 75% RH and HI concrete drying at 50% RH. The data are consistent with the well documented hysteresis between sorption/desorption isotherms. Concretes containing silica fume (SF) and ground granulated blast-furnace slag (GGBS) did not exhibit such hysteresis. Reducing the surface tension of the pentrating solution profoundly reduced the sorptivity into dried specimens but not the depth of penetration or the steady state wick action rate. Direct measurements on osmotic flow through vacuum saturated specimens showed that osmotic effects had a limited effect on wick action at salt concentrations expected in most environmental conditions. / The research demonstrates that desorptivity from the drying surface rather than sorptivity into the wetting surface is the dominant factor determining wick action through concrete. The ease with which desorptivity can be measured and the simple empirical model developed provides practicising engineers with a useful tool to estimate water transport due to wick action through concrete in partially immersed conditions.
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Fôrmas para concreto: subsídios para a otimização do projeto segundo a NBR 7190/97 / Formwork for concrete: subsidies to optimizing the design according NBR 7190/97 (Brazilian Code - Design of Timber Structures)Maranhão, George Magalhães 31 July 2000 (has links)
O elevado nível de conhecimento na fabricação de novos materiais e nas etapas da elaboração do projeto de estruturas não se repete quando são avaliadas as técnicas de execução de edificações. Por outro lado, a economia globalizada tornou indispensável a racionalização na construção civil e, no que refere ao item fôrmas, esta só é possível com o ação de um profissional especializado, ainda raro no mercado de trabalho da engenharia brasileira. Neste contexto, este trabalho apresenta procedimentos para se alcançar a redução no custo final da construção quando bem delineados os projetos arquitetônico e estrutural, com ênfase em aspectos construtivos. São também mostrados os benefícios da correta definição do \"Projeto de Fôrmas\", necessidade imperiosa no conjunto de elementos gráficos que constituem o projeto de um edifício. Os princípios e as técnicas para a análise e o projeto das fôrmas para estruturas de concreto são apresentadas de acordo com a nova versão da norma brasileira (Projeto de Estruturas de Madeira - 1997), fundamentada no método dos estados limites. Os ensaios experimentais realizados nas faces laterais das fôrmas dos pilares definem uma proposta de formulação para o cálculo da pressão lateral que o concreto exerce nessas faces (segundo a teoria de Mohr-Coulomb), necessário para o dimensionamento de peças integrantes das fôrmas. Por fim, são apresentadas as premissas para a elaboração projetual de um sistema de fôrmas para edifícios de múltiplos andares. / The high level of knowledge in the production of new materials and in the steps of structural design is not present on the construction techniques of multistorey buildings. On the other hand, to global economy it becomes indispensable to introduce rationalization concepts in civil construction, especially in formwork. This introduction is only possible with the action of an expert, who is still rare in Brazilian Civil Engineering. In this context, this work aims the presentation of procedures to reach a reduction on the final cost of multi-storey buildings, when architectural and structural design are well outlined, with emphasis to constructive details. Furthermore, the benefits of a proper definition of the \"Formwork Design\" are presented, due to its fundamental role in the graphical elements of a project. The principles of formwork design are presented according to new Brazilian Code (Design of Timber Structures -1997), based on limit states method. Tests on the lateral faces of column formwork originated a proposal to estimate lateral pressures applied by the concrete (according to Mohr-Coulomb Theory), which is necessary to detail formwork elements. Finally, the premises to design the formwork of a multistorey building are presented.
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Fôrmas para concreto: subsídios para a otimização do projeto segundo a NBR 7190/97 / Formwork for concrete: subsidies to optimizing the design according NBR 7190/97 (Brazilian Code - Design of Timber Structures)George Magalhães Maranhão 31 July 2000 (has links)
O elevado nível de conhecimento na fabricação de novos materiais e nas etapas da elaboração do projeto de estruturas não se repete quando são avaliadas as técnicas de execução de edificações. Por outro lado, a economia globalizada tornou indispensável a racionalização na construção civil e, no que refere ao item fôrmas, esta só é possível com o ação de um profissional especializado, ainda raro no mercado de trabalho da engenharia brasileira. Neste contexto, este trabalho apresenta procedimentos para se alcançar a redução no custo final da construção quando bem delineados os projetos arquitetônico e estrutural, com ênfase em aspectos construtivos. São também mostrados os benefícios da correta definição do \"Projeto de Fôrmas\", necessidade imperiosa no conjunto de elementos gráficos que constituem o projeto de um edifício. Os princípios e as técnicas para a análise e o projeto das fôrmas para estruturas de concreto são apresentadas de acordo com a nova versão da norma brasileira (Projeto de Estruturas de Madeira - 1997), fundamentada no método dos estados limites. Os ensaios experimentais realizados nas faces laterais das fôrmas dos pilares definem uma proposta de formulação para o cálculo da pressão lateral que o concreto exerce nessas faces (segundo a teoria de Mohr-Coulomb), necessário para o dimensionamento de peças integrantes das fôrmas. Por fim, são apresentadas as premissas para a elaboração projetual de um sistema de fôrmas para edifícios de múltiplos andares. / The high level of knowledge in the production of new materials and in the steps of structural design is not present on the construction techniques of multistorey buildings. On the other hand, to global economy it becomes indispensable to introduce rationalization concepts in civil construction, especially in formwork. This introduction is only possible with the action of an expert, who is still rare in Brazilian Civil Engineering. In this context, this work aims the presentation of procedures to reach a reduction on the final cost of multi-storey buildings, when architectural and structural design are well outlined, with emphasis to constructive details. Furthermore, the benefits of a proper definition of the \"Formwork Design\" are presented, due to its fundamental role in the graphical elements of a project. The principles of formwork design are presented according to new Brazilian Code (Design of Timber Structures -1997), based on limit states method. Tests on the lateral faces of column formwork originated a proposal to estimate lateral pressures applied by the concrete (according to Mohr-Coulomb Theory), which is necessary to detail formwork elements. Finally, the premises to design the formwork of a multistorey building are presented.
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