Seismic performance of shear critical post-heated reinforced concrete square columns wrapped with FRP composites

This paper describes the results of an experimental study carried out to investigate the seismic performance of post-heated reinforced concrete square columns repaired with unidirectional glass or carbon fibre reinforced polymers (GFRPs or CFRPs). The test specimens were categorized into three groups; (a) un-heated, (b) post-heated and (c) post-heated columns repaired with GFRP or CFRP jackets. Each group consisted of two columns with a shear-span-to-depth ratio of 2.5 tested under similar conditions comprising a constant axial and a lateral cyclic load simulating earthquake loading. The main variables investigated in this experimental study were the effect of heat damaged columns, the type of fibres used for repair, the orientation of the main fibres and the peak drift ratios achieved. The seismic performance of the GFRP or CFRP wrapped post-heated columns were compared to the reference un-heated and post-heated columns through the hysteretic response, shear resistance, lateral strength, ductility, energy dissipation and stiffness degradation. The test results showed that wrapping of columns with a single layer of GFRP or CFRP notably enhanced the shear capacity, ductility, energy dissipation ability and slowed the rate of strength and stiffness degradation. It was shown that the post-heated columns regained the lateral strength up to the original level of un-heated columns wrapped with a single layer of GFRP or CFRP. However, it was also shown that the post-heated columns wrapped with a single layer of GFRP or CFRP did not restore the repaired post-heated column to the original level of stiffness of the un-heated columns. Additionally, the un-heated and post-heated columns failed in shear while the governing failure mechanism of the GFRP or CFRP wrapped post-heated columns was successfully shifted from column shear to flexural failure.

► GFRP or CFRP notably enhanced the shear capacity, ductility and energy dissipation.
► GFRP or CFRP wrapped post-heated columns regained the original lateral strength.
► GFRP or CFRP slowed the rate of strength and stiffness degradation.
► GFRP or CFRP did not restore the original stiffness.
► GFRP or CFRP shifted the governing failure mechanism from shear to flexure.