Finite element modeling of reinforced concrete beams exposed to fire

The practical implementation of performance-based fire safety design of reinforced concrete (RC) structures hinges on the availability of accurate numerical simulation tools for the behavior of RC members exposed to fire. This paper presents a three-dimensional (3D) finite element (FE) model for the accurate prediction of both the thermal and the mechanical behavior of RC beams exposed to fire. In this FE model, particular attention is paid to the modeling of interfacial bond-slip behavior between the reinforcing steel and the concrete, an aspect which has rarely been considered by previous numerical studies. Results obtained from this FE model are compared with existing test data to examine the accuracy of the model. This comparison shows that the inclusion of the steel-to-concrete interfacial behavior leads to more accurate predictions of the deflection of RC beams exposed to fire. Predictions from this FE model also allow the complex distribution and evolution of stresses in the reinforcing steel and the concrete to be examined in detail, leading to a better understanding of the local responses of RC beams exposed to fire. The FE model presented in the paper can be used directly in performance-based fire safety design of RC beams; it can also be employed in parametric studies aimed at developing simple design rules.