MODELING OF THERMOMECHANICAL DAMAGE OF EARLY-AGE CONCRETE

The phenomena that occur during the early age of concrete curing are c omplex, as the coupling between chemical-thermal-hydration and mechani cal effects must be considered. Among the main attributes that govern the nonlinear behavior of early-age concrete are stiffness evolution, the development of thermal strains, creep, and cracking. To properly a ccommodate these effects in a finite-element analysis of a large struc ture such as a concrete dam, efficient computational strategies are ne eded. In this paper, a finite-element numerical algorithm is developed for analyzing thermomechanical damage in young concrete. Thermal anal ysis procedures include consideration of heat generation (hydration) a nd dissipation within mass concrete, including the effects of ambient temperature. The stress-deformation-damage analysis procedures include temperature-induced, creep, and autogenous deformations. Development of concrete properties, including Young's modulus, tensile strength, a nd limiting tensile strain is described by experimentally obtained fun ctions. Damage in concrete is considered to be the result of crushing, cracking, and a mixed failure mode. Failure criteria for each failure mode, along with constitutive relationships for prefailure and postfa ilure states are developed for both loading and unloading conditions. The developed finite-element program is used to simulate the construct ion of the first four layers of a concrete dam. The cracking damage pr edicted by the finite-element analysis is shown to qualitatively match with field observations.