Análise computacional do dano em estruturas de concreto submetidas a altas temperaturas

Abstract

Concrete is a handy mixture of typical components of the earth’s surface. It is associated with the fact that it does not require highly qualified labor for its production and good thermal and mechanical performance, making it the most used construction material. In this context, urban development and the consequent evolution of civil construction provided an increasing sophistication of concrete structures, implying increasingly severe requests for use, as in the case of submission to thermal gradients, which may be part of the condition of use of the structure, and be planned in design, or occur accidentally through fires. Therefore, it is necessary to develop realistic models capable of reliably predicting these structures’ behavior. However, this is not a simple process. Once the microstructure of this material is highly complex and heterogeneous, what is associated with the cracking mechanisms, results in its non-linear behavior. Aiming to contribute to this scenario, the thermomechanical behavior of concrete structures submitted to high temperatures was analyzed computationally, using a set of experimental data provided by the Cergy-Pontoise University in France. For this, two-dimensional and three-dimensional synthetic specimens were generated, from which simulations were made using the commercial finite element program Abaqus and its subroutine resource. Through the implementation of the Mazars (1984) damage model, the damage evolution was evaluated, comparing the results of the considered geometries, verifying the congruence between them. For this purpose, inverse problems were used to obtain unknown parameters and properties, and three models were developed, one elastic, one thermal and one thermomechanical. Subsequently, the study of the influence of the parameters of the damage model Mazars (1984) on the evolution of Young’s modulus was carried out. Finally, the impact of the granulometry and the relative volume of the aggregates on the concrete damage process was evaluated. The results obtained attest to the effectiveness of the proposed methodology.