Finite-element modeling of deformation and cracking in early-age concrete

The main nonlinear phenomena that govern the deformational behavior of early-age concrete are the evolution of the stiffness properties, the development of thermal strains, creep, and cracking. A general approach for numerically simulating this type of behavior is presented. The thermomechanical problem is decoupled such that first a thermal analysis is carried out and then a stress calculation is performed. An interface program is used to map the results from the thermal analysis onto the input data required for the stress analysis. A brief review of the relations for the thermal-stress analysis is given, followed by a more elaborate treatment of the algorithm used for the combination of thermal strains, creep, and smeared cracking. To properly accommodate these effects in a finite-element analysis, a smeared-crack model is used that is rooted in a decomposition of the strain increments. The emphasis is on the general approach for properly and efficiently handling these phenomena. A special case, namely a power-type creep law, is elaborated. It is shown that this relationship reasonably fits experimental data. A detailed description of an example calculation that demonstrates the potential of the numerical simulation strategy follows