Effect of corrosion damage on seismic behaviour of existing reinforced concrete beam-column sub-assemblages

Environmental degradation of reinforced concrete (RC) in the form of reinforcement corrosion poses greater threat to both strength and serviceability of existing RC structures. If this corrosion damaged structures are situated in the zones of higher seismicity, there would be a great threat to their safety under earthquakes and hence it is extremely important to understand their seismic performance in order to formulate suitable remedial measures. In view of this, in present study, an exterior beam-column sub-assemblage of a residential building is taken up and is designed for two levels, namely (i) designed for seismic load without ductility detailing (non-ductile specimen), and (ii) designed for lower seismic load and with ductility detailing (ductile specimen) to represent the existing RC structures of different design evolutions. Two specimens are cast for each level of design and one specimen from each of these two categories is subjected to accelerated corrosion. The experimental investigations are carried out on the uncorroded and corroded beam-column sub-assemblages under reverse cyclic loading. Corrosion of reinforcement changed the damage progression from joint shear failure to longitudinal and splitting cracking along the reinforcement bars followed by fracturing of corroded reinforcement bars. The corroded specimens showed poor hysteretic performance in the form of huge in-cyclic strength degradation. Furthermore, the cumulative energy dissipated by corroded non-ductile and corroded ductile specimens are respectively only 0.4 times and one-seventh of that of the corresponding uncorroded specimens. Thus, the seismic performance of corrosion affected existing structure is an alarming issue and warrants immediate retrofit intervention.