Modeling of concrete nonlinear mechanical behavior at high temperatures with different damage-based approaches

Heating of concrete leads to decrease of mechanical properties due to different damage processes: thermal strain gradients, chemical reactions, increase of vapour pressure (which is not taken and strain incompatibilities (between cement paste and aggregates, which is not taken into account explicitly here). This research project deals with comprehension of mechanical modeling (smeared cracking approach) on concrete's behavior at high temperatures so as to be able to predict the previous mechanical damage processes and properties decreases. Two types of mechanical models are used: an isotropic elastic damage model (IED) and an orthotropic elasto-plastic damage model (OEPD). Transient thermal creep model (TTC) is also introduced. Different temperature rates are investigated and different virtual mechanical tests are performed (uniaxial tension, uniaxial compression, biaxial tension). The paper concludes, using numerical analysis and comparisons to experimental results, on relevances and performances of these different mechanical models.