Numerical modeling of failure processes in steel fiber reinforced cementitious materials

• Grant number: 09/07451-2
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: January 01, 2010
• End date: November 30, 2014
• Field of knowledge: Engineering - Civil Engineering - Structural Engineering
• Principal Investigator: Tulio Nogueira Bittencourt
• Grantee: Luís Antônio Guimarães Bitencourt Júnior
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 04/03049-1 - Monitoring and evaluation of deformability, cracking and safety of concrete structures, AP.TEM
• Associated scholarship(s): 12/05430-0 - Computational modeling of fiber reinforced brittle materials, BE.EP.DR

Abstract

This work presents a numerical strategy developed using the Finite Element Method (FEM) to simulate the failure process of Steel Fiber Reinforced Cementitious Composites (SFRCCs). The material is described as a composite made up by three phases: a cementitious matrix (paste, mortar or concrete), discrete discontinuous fibers, and a fiber-matrix interface.A novel coupling scheme for non-matching finite element meshes has been developed to couple the independent generated meshes of the bulk cementitious matrix and a cloud of discrete discontinuous fibers based on the use of special finite elements developed, termed Coupling Finite Elements (CFEs). Using this approach, a non-rigid coupling procedure is proposed for modeling the complex nonlinear behavior of the fiber-matrix interface by adopting an appropriate constitutive damage model to describe the relation between the shear stress (adherence stress) and the relative sliding between the matrix and each fiber individually. This scheme has also been adopted to account for the presence of regular reinforcing bars in the analysis of reinforced concrete structural elements.The steel fibers are modeled using two-node finite elements (truss elements) with a one-dimensional elastoplastic constitutive model. They are positioned using an isotropic uniform random distribution, considering the wall effect of the mold.Continuous and discontinuous approaches are developed to model the brittle behavior of the bulk cementitious matrix. For the former, an isotropic damage model including two independent scalar damage variables for describing the composite behavior under tension and compression is considered. The discontinuous approach is based on a mesh fragmentation technique that employs degenerated solid finite elements in between all regular (bulk) elements. In this case, a tensile damage constitutive model, compatible with the Continuum Strong Discontinuity Approach (CSDA), is proposed to predict crack propagation. To increase the computability and robustness of the continuum damage models used to simulate the failure processes in both of the strategies, an implicit-explicit integration scheme is used.Numerical analyses are performed throughout the presentation of the work. Initially, numerical examples with a single reinforcement are presented to validate the technique and to investigate the influence of the fiber's geometrical properties and its position relative to the crack surface. Then, more complex examples involving a cloud of steel fibers are considered. In these cases, special attention is given to the analysis of the influence of the fiber distribution on the composite behavior relative to the cracking process. Comparisons with experimental results demonstrate that the application of the numerical tool for modeling the behavior of SFRCCs is very promising and may constitute an important tool for better understanding the effects of the different aspects involved in the failure process of this material.

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

BITENCOURT, JR., LUIS A. G.; MANZOLI, OSVALDO L.; TRINDADE, YASMIN T.; RODRIGUES, EDUARDO A.; DIAS-DA-COSTA, DANIEL. Modeling reinforced concrete structures using coupling finite elements for discrete representation of reinforcements. FINITE ELEMENTS IN ANALYSIS AND DESIGN, v. 149, p. 32-44, SEP 15 2018. (12/05430-0, 09/07451-2)

BITENCOURT JR, LUIS A. G.; MANZOLI, OSVALDO L.; BITTENCOURT, TULIO N.; VECCHIO, FRANK J.. Numerical modeling of steel fiber reinforced concrete with a discrete and explicit representation of steel fibers. INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, v. 159, p. 171-190, MAR 2019. (12/05430-0, 09/07451-2)

Academic Publications

(References retrieved automatically from State of São Paulo Research Institutions)

BITENCOURT JÚNIOR, Luís Antônio Guimarães. Numerical modeling of failure processes in steel fiber reinforced cementitious materials.. 2014. Doctoral Thesis - Universidade de São Paulo (USP). Escola Politécnica (EP/BC) São Paulo.