Description
The traditional method for satisfying fire resistance requirements of reinforced concrete (RC) structures is to provide adequate concrete cover depth. However, excessive concrete cover depth may increase the risk of concrete spalling during a fire and result in a wider crack width. The structure will be difficult to repair due to the large residual deformation after fire. Iron-based shape memory alloys (Fe-SMA) can be activated and produce recovery stress when exposed to fire, a natural heat source. The recovery stress can reduce the deformation and improve the mechanical properties of concrete structures. Therefore, a novel active approach based on the Fe-SMA is proposed in this study to investigate the feasibility of improving the fire performance of RC structures through the recovery stress generated by Fe-SMA under fire. The fire test of Fe-SMA RC beams was conducted. The mid-span deflection of the Fe-SMA RC beams was significantly reduced. The fire resistance of the Fe-SMA RC beams was 35%-49% higher than the conventional RC beams. The residual deformation was reduced by about 20%-40%, and the crack width was decreased by about 30%-90%. In addition, Fe-SMA can develop permanent prestress after cooling to room temperature, improving the mechanical properties after the fire. The residual bearing capacity of the Fe-SMA RC beams was 21% higher than the conventional RC beams. The residual stiffness of Fe-SMA RC beams was approximately 86%-121% higher than the conventional RC beams. The experimental results show that the Fe-SMA has great potential in improving the fire performance of RC structures.
