Behaviour of Reinforced Concrete Frames in a Fire Environment Including Transitional Thermal Creep

Abstract

SummaryA finite element code based on the total Lagrange co-rotational formulation is presented for the non-linear analysis of reinforced concrete frames under severe thermomechanical loads. The formulation makes use of a tangential operator derived by integrating the stress-strain rate laws of concrete and steel at elevated temperatures. It also includes geometrical nonlinear effects stemming from the resulting large displacements, degradation of the elastic and inelastic material properties with temperature. For concrete, it also accounts for cracking and crushing, as well as transitional thermal creep that develops under first-time heating. Comparisons with experimental results show that the code yields fairly good results. The code is also used to analyse a reinforced concrete frame subject to an hypothetical fire, and investigate the effect of transitional creep on its behaviour. It was found to perform reasonably well when compared to equivalent software. Transitional thermal creep was found to cause stress relaxation and distribution in elements predominantly subject to bending.