Behavior of prestressing steels after a simulated fire: Fire-induced damages

Fire safety should consider not only the performance of the structure during the fire but also the behavior after cooling. Even if a fire does not give rise to apparent damage in the prestressed structure, mechanical properties of materials as well as load distribution can be affected. A verification of residual load-bearing capacity is necessary to determine if the structure can be maintained in use. In this work, the behavior of prestressing steels during and after fire has been studied. We have attempted to clarify two aspects that should be considered when assessing the security of the structures: the reduction of the prestressing loads due to the increment in the stress relaxation losses during exposure to high temperatures and the permanent damage of the residual mechanical properties of steel wires produced by high temperatures. This paper seeks to give a comprehensive and extensive explanation, in addition to a simplified estimation of the non-visible fire-induced damages produced in steel wires, with the hope that this information can be useful for engineers in the structural evaluation after a fire.