Seismic performance and reparability assessment of recycled aggregate concrete columns with ultra-high-strength steel bars

In this paper, ultra-high-strength steel bars (UHSS) were innovatively applied to the high-strength recycled aggregate concrete (HSRAC) columns to achieve resilient structures cast from green building materials. Quasi-static tests of five new pattern columns were conducted to investigate the seismic performance and reparability. The influence of UHSS substitution ratio and the recycled coarse aggregate replacement ratio on seismic response and damage evolution of HSRAC columns were discussed. The research showed that configuring UHSS in the HSRAC columns could obtain drift-hardening property, and the residual displacement and crack width meet the requirements of repairable limit at the drift ratio less than 3%. The application of recycled aggregate concrete had negligible effect on the seismic performance and reparability of columns, and even contributed to improve their reparability probability. Moreover, reparability assessment methods were established based on the damage evolution theory and measured results, the prediction models of skeleton curve and reparability probability of HSRAC columns were proposed. The models were then verified by comparing the prediction results with test results.