Uma contribuição para modelagem numérica do concreto com fibras curtas de aço

Abstract

Concrete elements under certain conditions, such as high tensile stresses, present a brittle behavior which has to be avoided. In this context, steel fiber reinforced concrete (SFRC) proves to be a feasible solution. Random addition of short steel fibers to concrete leads to a pseudoductile behavior through an increase in the energy absorption capacity due to fibers. Although abundant experimental investigations concerned with SRFC have been done so far, less extensive research has dealt with the numerical modeling of SFRC. This work is a contribution to this research area. The objective of this thesis is to present the results of a proposed numerical modeling of SFRC beams behaviour, acquired from a nonlinear finite element analysis. The main characteristic of the proposed model is a trilinear tensile stress-strain diagram, which improves the representation of the toughness increase provided by the steel fibers addition. Two branches of the model are discussed, supported by a trilinear constitutive law whose parameters are obtained from the mechanical properties of the material. The model is incorporated to an academic open-source computational package that employs the object-oriented tool, which was expanded during the implementation of the proposed model. The validation of the proposal is done through numerical simulations of plane-state problems in SFRC beams. Three and four-point bending on SFRC specimens for different types of short steel fibers as well as a range of fiber contents are numerically investigated. One proposes a methodology for application of one of the sources of the model. Good correlation in the load x displacement relationship is achieved, proving the compliance of proposed model and methodology.