Repair of Fire-Exposed Preloaded Rectangular Concrete Columns by Postcompressed Steel Plates

This paper describes an experimental study of axially loaded, fire-exposed, rectangular RC columns repaired with postcompressed steel plates. Seven RC columns with identical section dimensions and reinforcement details were fabricated and tested. Six of these were exposed to a 4-h fire load according to the ISO 834 standard. After 1 month of cooling, five of the fire-exposed columns were installed with precambered steel plates, which were then postcompressed by a method newly developed by the authors. All columns were tested under axial compression to determine their ultimate load capacity, deformation, and ductility. The effects of steel-plate thickness, initial precamber displacements, and preloading level on the ultimate load capacity of repaired RC columns were investigated. The test results show that up to 72% of the original capacity of the axial load-carrying capacity of fire-exposed columns repaired with postcompressed steel plates can be restored. Furthermore, the repaired specimens show better ductility and postpeak deformability. An analytical model was adopted to predict the ultimate axial load capacity of fire-exposed columns repaired with postcompressed steel plates. The comparison of the theoretical and experimental results reveals that the analytical model can accurately predict the ultimate axial load capacity of the repaired columns.