Influence of fire scenario on dynamic behavior of RC columns in structures: A refined simulation

Reinforced concrete (RC) columns, as a main vertical load-bearing structural component, may be seriously damaged in the event of fire and explosion accidents, thereby affecting the safety of the building. In the current work, the lateral impact resistance of RC columns under two fire scenarios (at high temperature or after cooling from high temperature) is discussed using a 3D mesoscopic model. In the modeling process, the heterogeneity of concrete and the bond-slip behavior between longitudinal reinforcement and concrete were taken into account. In addition, the differences in impact resistance of RC columns at high temperature and after cooling with different fire durations were analyzed, and some quantitative conclusions were given. The results show that the mesoscopic numerical model considering the relative slip of steel bar and concrete can reasonably reflect the mechanical response of the RC column under impact load or fire. Exposure to the same fire duration, the impact resistance of the RC column at high temperature is weaker than that after cooling due to the severe deterioration of material mechanical properties at high temperature. The damaged area and the maximum plastic strain of the column increased as the fire duration increased. The mid-span peak and residual deflection of columns increase linearly with the increase of fire duration. Under the same fire scenario, the peak and residual impact force of the column increases nonlinearly with the fire duration, while the peak reaction force decreases linearly. The fire scene has little effect on the axial force, shear force and bending moment of the RC column under the same fire duration. In addition, the mechanical behavior of the column ends and mid-span areas need to be considered in the design due to their obvious changes in internal forces.