Meso- and Macroscopic Models for Fiber-Reinforced Concrete

Fiber reinforced concrete is analyzed and modeled at two different levels of observation. On the one hand, a macroscopic formulation based on the non-linear microplane theory is presented. Following approaches recently proposed in Pietruszczak & Winnicki (2003) and Manzoli et al. (2008), the mixture theory is used to describe the coupled action between concrete and the fiber reinforcement. The parabolic Drucker- Prager maximum strength criterion is considered at the microplane level. Post-peak behavior is formulated in terms of the fracture energy release under mode I and/or II failure modes. On the other hand, a mesoscopic model of fiber reinforced concrete (FRC) is also presented which is based on three constituents: aggregate, mortar and aggregate-mortar interfaces. Aggregates are considered to be elastic while cracks are represented in a discrete format by means of interface elements. The presence of steel fibers is considered within the framework of the mixture theory. Consequently, mortar-mortar interfaces account for both fiber-mortar debonding and dowel effects according to the fiber volume content. After describing the constitutive models the paper focuses on numerical analysis of FRC failure behavior including re-analyzes of the experimental tests of Hassanzadeh (1990). The capabilities and shortcomings of both approaches for FRC failure analyses are evaluated.