In major earthquakes, reinforced concrete (RC) frame collapse often occur due to severe damage developed within the columns. To delay and control the damage of RC columns, the author previously developed the RC self-centering and energy-dissipating rocking column base system with low-damage characteristics. Further, engineering cementitious composites (ECC) of various compositions were used to repair damaged RC columns in past studies. Amongst them, basalt fiber ECC (BF-ECC) is renowned for its economic advantage over other ECC materials while maintaining comparable mechanical performances. In this study, spray BF-ECC was used to repair the damaged rocking column base used in pervious experiments. In pervious experiments, the column base was loaded with hysteresis loading scheme from 0.5% to 2% drift, and then from 0.5% to 5.5% drift, respectively. The damaged concrete cover of the rocking column base was removed, the height of the removal region is equal to the width of the column base. High workability BF-ECC specifically designed for spraying was applied to form the new concrete cover, the surface finishing was applied manually. The entire retrofit process which involves removal of concrete cover, spray BF-ECC and replacement of column dampers took about 2 hours. The repaired column base was placed under hysteresis loading from 0.5% to 5.5% drift. The experiment found that compare to previous experiments, the column base exhibited more numerous and finer cracks while larger cracks occurred at the concrete-BF-ECC and steel-BF-ECC interfaces. Limited local crushing of the BF-ECC layer was observed at large drifts. It was also found that the peak loading capacity of the retrofitted column was equal to its RC counterpart, whereas its energy dissipation and ductility were improved by approximately 20%, respectively. Meanwhile, the performance targets of the rocking column base were met, demonstrating the superior repairability of the proposed column base.

Spray BF-ECC, Rocking Column-Base, Post-Earthquake Retrofit, RC Frame, Earthquake Resilience