COUPLED HYDRO-MECHANICAL AND DAMAGE MODEL FOR CONCRETE AS AN UNSATURATED POROUS MEDIUM

Abstract eng:
The long-term behavior of concrete is largely dependent, in many applications of civil engineering, of the transfer phenomena of the fluid phases filling the pores, which are governed by diffusion and permeation processes (shrinkage, creep). In this study the concrete is described as a porous medium made up of two phases (solid and liquid) in interaction by using the mechanics of isothermal unsaturated porous media. Two isotropic damage variables are introduced in the formulation for reproducing the degradations appearing in tension and compression, as well as their effects on the hydro-mechanical coupling parameters. The main transfer phenomenon is assumed to be controlled essentially by pore water pressure gradients, and consequently the capillary pressure, related to the saturation degree via the desorption isotherm curve, defines the state of the liquid phase. Under this hypothesis the governing equations are established in function of the capillary pressure in the case of the drying shrinkage of concrete. The analogy between the proposed simplified formulation and the more classical problem of a saturated porous medium is briefly analyzed.

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