A positional formulation of the embedded bar with uniaxial, shear and flexural stiffness for the reinforced concrete analysis considering physical nonlinearities

• Autor(a) principal: Albuquerque, Arthur Álax de Araujo
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/18/18134/tde-26112019-124050/
• topic: Armadura embutida; Crack Models; Damage model; Dowel Action; Efeito pino; Elementos finitos; Embedded reinforcement; Finite Elements; Fracture Mechanic; Mecânica da Fratura; Mecanismo de cisalhamento; Modelo de dano; Modelos de fissuração; Shear mechanism

Nowadays, the representation of reinforcement bars in composite materials, such as the reinforced concrete, is an important role that needs to be properly evaluated in numerical analysis with the finite element method. For this reason, researches that supply useful information about different ways to represent such reinforcements has commonly been explored. The matrix and fibers terminology is frequently adopted in numerical research to refers to the two materials: concrete and steel, respectively. Currently, only bars with the uniaxial stiffness have been assumed to the analysis of the reinforced concrete. However, some structures, in which the collapse mechanism is related to the dowel action phenomenon, must be evaluated with fibers represented by finite elements that take into account the uniaxial, flexural and shear stiffnesses. The use of frame finite element is an option to the solution of this problem. In this context, this research addresses a computational code using FEM with positional formulation approach to simulate the structures mentioned with embedded bar formulation. Thus, this code enables the analysis of structural elements whose shear effects in the fibers produce a global relevant behavior. The physical nonlinearities for the matrix and fibers elements are taken into account to better discuss the effects of such additional stiffnesses. The one-dimensional and plane-stress plasticity theories are studied and implemented in the developed code, being used by the bar and the frame elements, respectively. Two damage models related to the smeared crack models approach are suggested to represent the degradation of the matrix elements. Several examples are explored to investigate the theory proposed. It is showed that for the analysis of structures in which the shear mechanism is not a preponderant effect the consideration of the fiber with additional flexural and shear stiffnesses produce similar results when compared with analysis performed by fibers with only uniaxial stiffness. However, for the cases in which the dowel action is significant, a more appropriate analysis is carried out when the fiber elements present such additional stiffnesses.