3D numerical analysis of reinforced concrete beams exposed to elevated temperature

Numerical results of the behaviour of reinforced concrete (RC) beams subjected to elevated temperatures followed by mechanical loading are discussed. The model used in the study is a transient three-dimensional thermo-mechanical model that was implemented into a three-dimensional (3D) finite element (FE) code. The mechanical constitutive law for concrete is the temperature dependent microplane model. The experimental details of the investigated RC beams are taken from the literature and the same loading scenarios are numerically simulated. The beams are analysed for the case of four-point bending with no fire load and for the post fire cases with three different exposure times. The numerically predicted load–deflection curves, temperature fields, strains and stresses and crack patterns (damage) of the beams exposed to high temperature and mechanical load are analysed and compared with the experimental results. It is shown that the employed numerical modeling technique can successfully predict the behaviour of the RC beams under mechanical load, fire and fire followed by mechanical load. Therefore, the used 3D thermo-mechanical model is useful numerical tool for the realistic prediction of the behaviour of concrete and RC structures exposed to high temperature.

► 3D FE study of RC beams exposed to elevated temperature is performed.
► 3D thermo-mechanical model for concrete that is employed in the study is described.
► Constitutive law for concrete is based on the temperature dependent microplane model.
► After exposure to fire the resistance and stiffness of the RC beams is reduced.
► The used model is able to realistically predict behaviour of RC beams under fire.