LATERAL IMPACT BEHAVIOR OF CFRP-REINFORCED CIRCULAR CONCRETE-FILLED STEEL TUBULAR MEMBERS AFTER EXPOSURE TO FIRE

The numerical model for the lateral impact of circular concrete-filled steel tubular (CFST) members after exposure to fire with and without carbon fiber reinforced polymer (CFRP) is established. The accuracy of the model is verified by different experiments. The whole impact process of reinforced post-fire members is analyzed. The impact force, mid-span deflection and sectional moment of the specimens are compared. In addition, the impact resistance and flexural capacity, plastic deformation and energy absorption capacity, as well as the distribution and development of the internal force are investigated. A simplified calculation formula for the maximum mid-span deflection of the specimens under impact load is proposed. The influence of CFRP reinforcement methods on the impact performance of the post-fire specimens is discussed. The results show that the plateau value of the impact force and the average sectional moment of post-fire specimens were increased by the CFRP reinforcement. However, the mid-span deflection and impact duration were significantly reduced. The impact resistance and flexural capacity of the specimens were significantly improved by the CFRP reinforcement. The impact resistance, flexural capacity and energy absorption capacity gradually decrease with the increase of the fire duration. In addition, the specimens experienced different degrees of plastic deformation at the span, and the energy was mainly absorbed by the formation of plastic hinges. The bending moment and shear force distributions of the specimens under lateral impact at the peak stage were different from those of the specimens under static load, but the distributions at the plateau stage were consistent with those of the specimens under static load. The simplified formula can well predict the maximum deflection of the specimens after lateral impact. The CFRP reinforcement methods have a noticeable influence on the impact resistance of post-fire members.