Experimental assessment of post-fire retrofitted RC columns tested under cyclic loading

Multiple combined hazards can affect the structures during their live span and may conditionate the future structural behaviour for some types of loading. That is the case of a structure previously damaged by fire and then loaded under seismic loading. For seismic hazard zones it is important assess the seismic performance of existing reinforced concrete (RC) structures designed according to old codes and without seismic detailing. This structural seismic assessment is even more important for buildings that were previously damaged by fire. Therefore, it is critical develop and validate fire retrofitting methods that can also improve the seismic behaviour. This paper presents the results of a novel experimental campaign carried out on four (two of them repaired and strengthened with CFRP wrapping after fire exposure) full-scale reinforced concrete columns previously damaged by a 30 or 90 minutes standard fire and then tested under uniaxial cyclic lateral loading up to failure. Moreover, two additional control columns, one as-built and another strengthened, were cyclically tested for comparison. A considerable decrease in the deformation capacity and dissipated energy was observed in the columns after fire exposure, even for the 30 minute fire. Moreover, the post-fire repaired and strengthened columns may reach similar seismic performance than analogous strengthened columns without previous fire damages.