Response of Reinforced Concrete Columns under Fire-Induced Biaxial Bending

Reinforced concrete (RC) columns, when exposed to fire, are often subjected to biaxial bending arising from eccentricity in loading or one-, two-, and three-sided exposure or due to nonuniform spalling. The effect of such biaxial bending is often not taken into consideration in evaluating the fire resistance of RC columns. In this paper, an approach is presented for modeling the fire response of RC columns under biaxial bending. This approach accounts for high-temperature material properties, geometric and material nonlinearity, fire-induced spalling, and restraint effects and can be applied under realistic fire and loading scenarios. The validity of the approach is established by comparing the predictions from the model with results from full-scale fire resistance tests. The model is applied to undertake a set of parametric studies and the results show that the biaxial bending effect arising from one-sided, two adjacent-sided, and three-sided fire exposure significantly decreases the fire resistance of RC columns.