Concreto nas primeiras idades: propriedades e modelagem termomecânica simplificada

• Autor(a) principal: Gomes, Flávio Mamede Pereira
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/0013000005qj1
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/3398
• topic: Concreto; Primeiras idades; Hidratação; Fluência; Viscoelasticidade; Termomecânica; Modelagem; Calorímetro; Concrete; Properties; Early ages; Hydration; Viscoelasticity; Thermomechamical; Modelling; Calorimeter; ENGENHARIA CIVIL::ESTRUTURAS

Large dimension concrete structures or those with restrictive conditions for heat dissipation are particularly subject to cracking in the early ages. Several phenomena may occur simultaneously, such as autogenous reactions, plastic shrinkage or drying, and temperature variations, leading to deformations which may be the main cause of cracking in the early ages of concrete, if the structure is restrained. Thus, the behavior of the concrete must be satisfactorily modeled and foreseen. The thermal and mechanic properties of concrete can be determined by standard tests or by prediction models, depending on the time and values established for the remaining thermal properties. The calculation methodology may become complex, considering the influence of temperature in the exothermic of the reaction, within the theoretical framework of the thermo-chemical-mechanical couplings. However, it may be simplified, as it is the aim of this paper to demonstrate. As for the mechanical behavior, concrete is considered a viscoelastic material. The simplifications are adopted in relation to the resources and time available, or in relation to the specifications of the problem to be modeled. The modeling of the concrete structures with simple geometry in the early ages, such as reservoirs, foundation block or retaining walls is made by considering the material simply as elastic for purpose learning the coefficient of restrain, which correlates the tension in a certain point of the structure to the tension in a restrained bar. This allows a swifter calculation of thermal tensions in a specific point in the structure, based solely in the history of temperature and degree of restrain, in addition to the properties of the material, which is valid for some boundary situations. This enables the technical personnel not specialized to access relevant information about preventive and mitigating measures to be adopted against undesirable effects.