Seismic strengthening of shear critical post-heated circular concrete columns wrapped with FRP composite jackets

An experimental study was carried out to investigate the seismic performance of post-heated circular reinforced concrete columns wrapped with glass or carbon fibre reinforced polymer jackets. Eight shear critical reinforced circular columns with a shear span-to-depth ratio of 2.5 were tested under a combined constant axial and cyclic lateral displacement history, simulating earthquake loading. The columns were tested in three groups, unheated, post-heated and post-heated repaired with either glass fibre reinforced polymer (GFRP) or carbon fibre reinforced polymer (CFRP). In terms of seismic performance the test results indicated that using GFRP or CFRP jackets significantly increased the shear capacity, ductility and energy dissipation of the post-heated damaged columns. However, the GFRP or CFRP did not increase the stiffness of the post-heated damaged columns. It was found that the unheated and post-heated damaged columns failed in a brittle shear mode while the mode of failure of posted-heated columns repaired with GFRP or CFRP was successfully shifted from a shear to a ductile flexural failure.