Critical Factors Governing the Residual Response of Reinforced Concrete Beams Exposed to Fire

Abstract

This paper presents results from a set of numerical studies on critical factors influencing residual response of fire exposed reinforced concrete (RC) beams. The numerical model, developed using finite element computer program ABAQUS, accounts for distinct material properties of reinforcing steel and concrete during fire exposure (both heating and cooling phases) and residual (after cool down) phase. In addition, residual plastic deformations that develop in the beam during fire exposure are also taken into consideration in evaluating post-fire response of RC beams. The validity of the model is established by comparing predictions from the numerical analysis with response parameters measured during fire and residual capacity tests. The validated model is employed to conduct a parametric study for varying fire intensity, level of loading (load ratio), restraint conditions, and cross-sectional sizes of the beam. Results from the parametric study indicate that load level has significant influence on both post-fire residual capacity, as well as residual deformations in the beam. The cross-sectional size of the beam also influences residual capacity and increasing the depth of section leads to improved residual capacity in the RC beam. Presence of axial restraint however, has only moderate influence on the residual response of RC beams exposed to fire. Moreover, under most parametric fire scenarios, RC beams can retain up to 70% of their room temperature capacity provided tensile rebar temperature does not exceed 450°C.