A multiaxial concrete model for applications in structural fire engineering

Temperature-dependent material models are required in numerical softwares dedicated to the
nonlinear analysis of structures in fire. Although structural concrete is widely used in civil engineering, proper modelling of its thermo-mechanical behaviour remains a challenging issue for engineers mainly because of the complexity of the phenomena that result from the microcracking process in this composite material and because of the lack of numerical robustness of the models. This paper presents a new multiaxial concrete model developed for the analysis of concrete structures in fire. The multiaxial model is based on a plastic-damage formulation and incorporates an explicit term for transient creep strain. After implementation in a finite element software for structural fire engineering calculations, numerical simulations have been performed to highlight the ability of the model to capture some of the main phenomena that develop in concrete (permanent strains, degradation of the elastic properties, unilateral effect) as well as the ability to be used for the fire analysis of large-scale structural elements.