Post-fire investigations of prestressed concrete structures

Concrete structures reinforced with prestressing steel, referred to as prestressed concrete (PSC) structures, are commonly used in bridge and tall building construction as they can easily be optimized. However, prestressing steel is well known to have complex behavior when exposed to high temperatures. To date, this structure’s high temperature behavior is not fully understood and can potentially complicate post-fire structural investigations of PSC structures. After a fire, it is often difficult to guarantee stability or specify necessary repairs for this type of structure. The study herein aims to help develop guidance for investigating and assessing PSC structures (with emphasis on bridge beams) post-fire. Investigations of specific and real PSC structures after fire exposure are reviewed as case studies herein. Characteristic damage indicators and test methods for assessment are discussed. The authors characterize the residual condition of a lab-scale PSC structure previously exposed to severe temperature. Nondestructive strength analyses of prestressing steel using a calibrated hardness test procedure were carried out. Results were compared to those from destructive methods and showed satisfactory correlation. The high temperature exposed concrete was also inspected. The paper concludes with recommendations of future research required to better identify the condition of PSC structures after fires