The three dimensional modelling of thermal cracks in concrete structure

Abstract

The occurence of thermal cracks in massive concrete structures is a common phenomenon. In order to modell this kind of cracks the material properties of hardening concrete, temperature and stress developments must be dealt with. According to Laube [1] the thermal and mechanical properties of concrete may be expressed as functions of the reference parameter—the degree of hydration which depends on the hardening time and on the temperature process, therefore, a non-linear coupled calculation of temperatures and stresses should be carried out. On the basis of these material laws a numerical modell is set up for the process simulations of the material properties, the temperature and the stress fields as well as the development of cracks. Then the modell is implemented into a three dimensional finite element programme. As an example a freshly concreted wall on top of an old foundation is investigated. Finally attention is paid to the numerical process modelling two typical thermal cracks,i.e. the surface cracks and the inner cracks, by employing the smeared approach of crack distributions in three dimensional hardening concrete.