A study was conducted to assess the influence of the steel reinforcement ratio in concrete columns on their properties of creep and shrinkage. Experimental tests and three-dimensional finite element-based simulations of the experimental curves from plain concrete cylinders and plain concrete columns derived by curve fitting were performed using the ACI 209 model available in DIANA 9.3. Columns with longitudinal reinforcement ratios of 0%, 1.4% and 2.8%, loaded to 30% and 40% of their 7-day compressive strength, were investigated. The results indicated that numerical simulation does not predict experimental data for a long period. However, simulations fitted with experimental curves derived from plain concrete columns presented values close to those of experimental data for 91 days.
This thesis presents the study of the time dependent deformation of concrete structures due to creep and shrinkage. Creep, shrinkage, compressive strength, splitting tensile strength and modulus of elasticity tests were performed in mixtures commonly used in construction. Experimental parameters were obtained from these mechanical characterizations and creep and shrinkage models were evaluated. Nine short reinforced and non reinforced columns were long term loaded and monitored for 91 days. The tests were performed in a temperature and relative humidity controlled ambient. The redistribution of internal stresses from concrete to reinforcement due to creep and shrinkage were investigated. In order to analyze the redistribution of internal stresses Finite Element Method simulations were performed. Creep and shrinkage models and experimental data were considered in simulations. Other formulations were also applied to examine the experimental data from columns. One of the creep models which best fit the experimental data of the column mixture characterization was adjusted and the model results were used in these formulations. Numerical results and experimental data were evaluated. In this context, the characterization of creep and shrinkage of concrete and statistical evaluation of models contribute to know the behaviour of present-day construction materials and makes possible the use of efficiency models. Besides the study of creep and shrinkage in columns enhance the knowledge of internal stresses redistribution. Finally, an updating creep model was successfully applied to concrete experimental data.
Resumo Creep has been pointed out as one of the main causes of non-structural cracking in concrete structures. Nevertheless, their behavior on concretes made with current materials is scarcely known. The use of real time health monitoring systems of strains in structures has been demonstrated to be a high potential inspection and maintenance techniques. The aim of this paper is to contribute for the publication of acquisition control techniques and strain results from a one month health monitoring period for Brazilian commercial concrete cylindrical specimens. For that, the equipment DataTaker and the DeTransfer software was used. Keywords: health monitoring, creep, data acquisition and concrete specimens.A fluência vem sendo apontada como uma das principais causas de patologias em estruturas de concreto. Todavia, o seu comportamento para concretos feitos com os cimentos nacionais atuais é conhecido de forma muito limitada. O uso de sistemas de monitoração de deformação em tempo real de estruturas tem demonstrado um grande potencial como técnicas de inspeção e manutenção. O objetivo deste trabalho é contribuir para a divulgação de técnicas do controle de aquisição e resultados referentes ao período de um mês de monitoração da deformação por fluência em corpos de prova cilíndricos considerando um concreto de linha de produção brasileiro. Para tanto, utilizaram-se o equipamento DataTaker e o programa DeTransfer.Palavras-chave: monitoração, fluência, aquisição de dados, corpos de prova de concreto.
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