Axial Behaviour of Post-Fire RC Columns Strengthened with Post-Compressed Steel Plates

Abstract

This paper describes an experimental study of axially loaded, fire-exposed, preloaded, rectangular RC columns repaired with post-compressed steel plates. Four RC columns were fabricated and tested. Specimen FSC1 was a control column that was not exposed to fire and without any strengthening measures. The other specimens were exposed to a four-hour fire load according to the ISO 834 Standard. After one month of cooling, three fire-exposed columns were installed with precambered steel plates which were then post-compressed by a method newly developed by the authors. This method can alleviate stress-lagging effects between the preloaded concrete core and steel jacketing which was generated from existing compression loading. All columns were tested under axial compression to determine their ultimate axial load-carrying capacity, deformation and ductility. During the axial compression test, the repaired columns were subjected to preloading before strengthening to simulate the real applications. The effects of steel plate thickness and initial precamber displacements on the ultimate load capacity of repaired RC columns were investigated. The experimental results show that precambered steel plates can share the existing axial load in the original RC column, and up to 72% of the original capacity of the axial load-carrying capacity of fire-exposed columns repaired with post-compressed steel plates can be restored. Meanwhile, the repaired specimens show better ductility and post-peak deformability.