Modeling R/C Columns in Fire according to Different Constitutive Models for Heated Concrete

Several analytical formulations aimed to describe concrete behavior at high temperature have been proposed in the past two decades, all of them taking into ac-count transient and creep strains, either explicitly or implicitly. The main objective of this paper is to compare some of the different models available in the literature, with reference to the structural behavior of long R/C columns exposed to fire, since these structural members are rather sensitive to thermally-induced deformations. To this end, a number of significant examples based on real-scale fire tests, characte-rized by well-defined geometry, loads and boundary conditions, were simulated numerically, by adopting different formulations for concrete behavior in compres-sion. In terms of displacements and time to failure, the comparisons clearly show that by using accurate constitutive laws (including – implicitly or explicitly – all strain components) a correct evaluation of the time to failure is possible. At the same time, no significant differences are observed among the various models, which means that the development of further models is not fully justified.