Seismic behavior of low-corroded reinforced concrete short columns in an over 20-year building structure

In reinforced concrete (RC) structures, reinforcement corrosion, concrete carbonization, and chloride ion erosion occur during service life, which deteriorate the seismic structural capacity of the structures. Most researchers have focused on the effect of the reinforcement corrosion on the seismic behavior of RC columns showing flexural behavior. On the other hand, research on the influence of the combined reinforcement corrosion and concrete carbonization on the seismic behavior of in-service RC columns showing shear-flexural behavior has not been performed. The present study evaluates the seismic performance of low-corroded in-service RC columns showing shear failure under cyclic load. Four RC columns with shear-span ratio 2.3 and light transverse reinforcement were obtained from an in-service RC moment frame building constructed in 1987, and quasi-static cyclic tests were conducted to investigate the seismic behavior of these columns. For the test parameters, axial compression force ratios and longitudinal bars arrangements were considered. The test results showed that as the compression force ratio increased, the failure modes of the in-service RC columns shifted from shear-bond failure to shear-compression failure, and the ductility and energy dissipation capacity decreased. The shear strength of the column specimens was evaluated by five existing shear strength models, considering the effect of reinforcement corrosion. Finally, seismic performance of RC short columns with corroded bars was discussed.