A multiaxial constitutive model for concrete in the fire situation: Theoretical formulation |
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Authors: | Thomas Gernay Alain Millard Jean-Marc Franssen |
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Affiliation: | 1. The National Fund for Scientific Research, Structural Engineering Department, University of Liege, Ch. Des Chevreuils 1, 4000 Liege, Belgium;2. CEA, DEN, DANS, DM2S, SEMT, LM2S, F-91191 Gif sur Yvette, France;3. Structural Engineering Department, University of Liege, Ch. Des Chevreuils 1, 4000 Liege, Belgium |
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Abstract: | This paper aims to develop a multiaxial concrete model for implementation in finite element software dedicated to the analysis of structures in fire. The need for proper concrete model remains a challenging task in structural fire engineering because of the complexity of the concrete mechanical behavior characterization and the severe requirements for the material models raised by the development of performance-based design. A fully three-dimensional model is developed based on the combination of elastoplasticity and damage theories. The state of damage in concrete, assumed isotropic, is modeled by means of a fourth order damage tensor to capture the unilateral effect. The concrete model comprises a limited number of parameters that can be identified by three simple tests at ambient temperature. At high temperatures, a generic transient creep model is included to take into account explicitly the effect of transient creep strain. The numerical implementation of the concrete model in a finite element software is presented and a series of numerical simulations are conducted for validation. The concrete behavior is accurately captured in a large range of temperature and stress states. A limitation appears when modeling the concrete post-peak behavior in highly confined stress states, due to the coupling assumption between damage and plasticity, but the considered levels of triaxial confinement are unusual stress states in structural concrete. |
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Keywords: | Thermomechanical processes Concrete Constitutive behavior Elastic–plastic material Damage model Fire |
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