LAUSR

Abstract Prestressing steel is commonplace in critical infrastructure like bridges. These structures are of significant societal and economic importance, and any disruptions affecting their service due to fire or other extreme events, can compromise life safety, structural integrity, and the economic cycle. The prestressing steel used in bridge infrastructure has been altered, chemically and mechanically, to attain high strength and durability properties, leading to complex behavior when exposed to high temperatures. The traditional guidance used by practitioners to assess prestressing steel post-fire performance are prescriptive charts that rely on the maximum temperature reached by the steel. These guidelines do not fully account for metallurgical changes introduced due to the time the steel was exposed to high temperatures, which has been shown in case studies to last up to eight or more hours in extreme conditions. Six prestressed bridge structures that were exposed to fire have been reviewed herein to discuss characteristic damage indicators and assessment methods. As part of the current work, multiple experimental programs are performed and other experiments by others are also reviewed, to analyse the residual condition of prestressed structures after fire. Non-destructive strength analyses coupled with calibrated hardness tests have been performed and compared to destructive methods with satisfactory correlation. Concrete exposed to high temperature was inspected, and research into the effect of exposure time on the post-fire strength of prestressing steel was examined. The results have shown that the current guidance relying only on critical temperature may not be conservative for long duration fires. Final remarks include suggestions for future research particularly for prestressed concrete and cable-supported structures, as well as recommendations to lower the critical temperature by at least 100 °C for current guidance to be applicable to longer durations fires.