A novel active fire protection approach for structural steel members using NiTi shape memory alloy

A novel active fire protection approach, based on integrating a shape memory alloy, NiTi, with a steel structure, was proposed to satisfy the fire resistance requirements in structural design. To demonstrate the principles of this approach, a simple structure in the form of a simply supported steel beam was used. The internal action of the beam due to a transverse applied load was reduced by utilizing the shape memory effect in the NiTi alloy at rising temperatures. As a result, the net internal action from the load design was kept below the deteriorated load capacity of the beam during the fire scenario for period of time that was longer than that of the original beam without the NiTi alloy. By integrating the NiTi alloy into the beam system, the structure remained stable even though the steel temperature exceeded the critical temperature which may have caused the original beam structure to collapse. Prior to testing the composite NiTi-steel beam under simulated fire conditions, the NiTi alloy specimens were characterized at high temperatures. At 300 degrees C, the stiffness of the specimens increased by three times and its strength by four times over that at room temperature. The results obtained from the high-temperature characterization highlighted the great potential of the alloy being used in fire engineering applications.