Effect of concrete cover thickness on deflection of reinforced concrete beams exposed to fire

Abstract

Fire is one of the extreme loads acting on constructional structures. When a fire occurs, fire causes negative effects on reinforced concrete (RC) structures. Specifically, fire increases the deformation demand and reduces the load-carrying capacity of RC structures. When these changes approach a certain extent, failure of structures occurs. RC beams, a part of structures, is directly affected by fire, in which the concrete cover plays an important role in the temperature of steel reinforcement. This paper presents the simulation results on the effects of concrete cover thickness on the deflection of RC beams exposed to fire. To achieve this aim, RC beams simultaneously subjected to loads and exposed to ISO 834 fire were analyzed. The simulations were performed using SAFIR software. The thermal analysis results were used to analyze the deflections of fire-exposed RC beams with respect to fire time. The analytical results show that the deflection increases almost linearly with the fire time in the first stage and then the nonlinearity increases rapidly until complete collapse. The thickness of concrete cover plays an important role on the relationship between the deflection and the fire time of RC beams. When the thickness of concrete cover increases from 20 mm to 45 mm, the fire resistance of RC beams increases by 67%.