Interpretation of stresses and strains in unsaturated fine-grained soils

The derivation of Eq. (1) relies on the soil particles and water phase combining and forming aggregates under equilibrium conditions. This may be shown to minimise the thermodynamic potential and is a requirement of equilibrium conditions. The equation has been shown to allow examination of the volumetric and anisotropic stress-strain behaviour both of the aggregates and between the aggregates in unsaturated fine-grained soils. The heterogeneous internal straining constitutes a level of straining between the macro-mechanical level and the micro-mechanical, particulate level

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