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Tolerâncias no dimensionamento e execução de elementos de betão armado
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Abstract(s)
Dada a complexidade e elevado número de intervenientes em obra, é difícil garantir rigor nas dimensões dos elementos de betão armado, pelo que podem existir algumas diferenças na geometria dos elementos estruturais construídos em relação ao definido em projeto. Assim sendo, e de modo a garantir que, não obstante a existência destas diferenças, o comportamento especificado exigido aos elementos estruturais não seja alterado, os regulamentos especificam um conjunto de valores, aos quais designam de tolerâncias dimensionais, que importa verificar.
As tolerâncias, definidas como sendo a diferença entre o limite superior e o limite inferior admissíveis para uma determinada dimensão, têm como principal objetivo limitar os possíveis desvios que possam ocorrer durante a fase de execução da estrutura, admitindo a possibilidade da ocorrência de uma pequena diferença entre as dimensões estabelecidas em projeto e as que são realmente executadas em obra.
Como ainda existe alguma dificuldade em interpretar e compreender o seu papel optou-se por realizar o presente trabalho.
Em primeiro lugar procedeu-se ao levantamento das tolerâncias especificadas nos principais regulamentos de estruturas de betão armado (Eurocódigos, Model Code 2010, Regulamento de Estruturas de Betão Armado e Pré-Esforçado e Normas Americanas) e em bibliografia de referência.
Numa segunda fase, fez-se uma análise mais detalhada ao estipulado no Eurocódigo 2 e na norma NP EN 13670 e, procedeu-se à seleção das tolerâncias que poderiam ter influência na resistência das secções dos elementos de betão armado e, consequentemente, na resistência estrutural.
Com recurso ao programa de cálculo automático GALA Reinforcement, e de modo a avaliar a influência das tolerâncias na resistência das secções, executou-se, de seguida, um pequeno estudo paramétrico num conjunto de secções de forma a avaliar a influência das tolerâncias nas resistências de vigas e pilares. Este estudo permitiu concluir que são os desvios na altura útil aqueles que têm maior impacto na resistência das secções.
De forma a que a resistência dos elementos estruturais não seja afetada pelas tolerâncias, considera-se necessário exigir maior rigor na altura útil das secções da viga, nas secções de pequena dimensão, nas secções muito armadas e nas dimensões das secções dos pilares (largura e altura útil da secção).
Due to the complexity and high number of people involved in construction site, it is difficult to guarantee accuracy in the dimensions of the reinforced concrete elements so that there may be some differences in the geometry of the structural elements constructed in relation to that defined in project. Thus, in order to ensure that, notwithstanding the existence of such differences, the specified behavior required of the structural elements is not altered, the regulations specify a set of values, which they designate as dimensional tolerances, which need to be checked. The main objective of tolerances, defined as the difference between the upper and the lower limit permissible for a given dimension, is to limit possible deviations that may occur during the execution phase of the structure, allowing the possibility of a small difference between the dimensions established in project and those actually carried out on site. As there are still some difficulties in understanding the role of dimensional tolerances defined by regulation, the present work was carried out, in which a detailed analysis of the tolerances specified by the main regulations of reinforced concrete structures is carried out. Firstly, the tolerances specified in the main regulations for reinforced concrete structures (Eurocodes, Model Code 2010, Regulations on Reinforced and Reinforced Concrete Structures and American Standards) and reference bibliographies were identified. In a second phase, a detailed analysis based on Eurocode 2 and in NP EN 13670 specifications to enable the selection of the tolerances that could have influence in the resistance of the reinforced concrete elements cross sections of and, consequently, in the structural resistance. Using the GALA Reinforcement automatic calculation program, and in order to evaluate the influence of the tolerances on the strength of the cross sections, the effective depth and the width of the section, a parametric study was performed. The study allowed to conclude that the allowed deviations for the effective depth are those that have greater impact in the section resistance. Finally, more attention should be given to the effective depth of elements cross sections, cross sections of reduced dimension, sections with high percentage of steel and columns cross sections, in order to ensure that the strength of the structural elements are not affected by tolerances.
Due to the complexity and high number of people involved in construction site, it is difficult to guarantee accuracy in the dimensions of the reinforced concrete elements so that there may be some differences in the geometry of the structural elements constructed in relation to that defined in project. Thus, in order to ensure that, notwithstanding the existence of such differences, the specified behavior required of the structural elements is not altered, the regulations specify a set of values, which they designate as dimensional tolerances, which need to be checked. The main objective of tolerances, defined as the difference between the upper and the lower limit permissible for a given dimension, is to limit possible deviations that may occur during the execution phase of the structure, allowing the possibility of a small difference between the dimensions established in project and those actually carried out on site. As there are still some difficulties in understanding the role of dimensional tolerances defined by regulation, the present work was carried out, in which a detailed analysis of the tolerances specified by the main regulations of reinforced concrete structures is carried out. Firstly, the tolerances specified in the main regulations for reinforced concrete structures (Eurocodes, Model Code 2010, Regulations on Reinforced and Reinforced Concrete Structures and American Standards) and reference bibliographies were identified. In a second phase, a detailed analysis based on Eurocode 2 and in NP EN 13670 specifications to enable the selection of the tolerances that could have influence in the resistance of the reinforced concrete elements cross sections of and, consequently, in the structural resistance. Using the GALA Reinforcement automatic calculation program, and in order to evaluate the influence of the tolerances on the strength of the cross sections, the effective depth and the width of the section, a parametric study was performed. The study allowed to conclude that the allowed deviations for the effective depth are those that have greater impact in the section resistance. Finally, more attention should be given to the effective depth of elements cross sections, cross sections of reduced dimension, sections with high percentage of steel and columns cross sections, in order to ensure that the strength of the structural elements are not affected by tolerances.
Description
Dissertação de Mestrado em Engenharia Civil
Área de Especialização: Estruturas
Keywords
Tolerâncias Regulamentação Betão Armado Dimensões Resistência Tolerances Regulation Reinforced Concrete Dimensions Resistance
Citation
Publisher
Instituto Politécnico de Setúbal. Escola Superior de Tecnologia do Barreiro.