Mechanical properties of prestressing steel after fire exposure

Prestressed concrete structures have been widely used all over the world, and there is a growing need to study the postfire repairability that is relevant whenever a fire occurs and no collapse happens after cooling. To evaluate the damage to the structure after fire exposure, the residual mechanical properties of structural materials need to be evaluated first. A literature review is conducted to analyse the major factors influencing the post-fire properties of prestressing steel. Existing test data are collected from an extensive survey of the available literature. Based on statistical analysis, the effects of heat exposure on the modulus of elasticity, yield strength and tensile strength, as well as ultimate strain, are analysed. A simplified stress-strain model is developed for prestressing steel in residual conditions (i.e. after heating and cooling to room temperature). Measured stress-strain curves are used to verify the accuracy of the proposed model.