Seismic performance and damage assessment of earthquake-damaged HSRAC columns with UHSS repaired by CFRP jackets

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 were conducted to investigate the seismic performance and reparability of HSRAC columns with UHSS under the first-excursion failure mode, and to analyze and discuss the effect of cumulative damage on earthquake-damaged resilient columns repaired by carbon fiber-reinforced polymer (CFRP) composites jackets. The research showed that the damage state of HSRAC columns at 2% drift ratio was mild, and residual displacement satisfied the reparability limit. And the earthquake-damaged resilient columns possessed satisfactory seismic performance after rapid repaired by CFRP jackets. Based on the experiment results and observations, a lateral load carrying capacity prediction model for HSRAC columns with UHSS under first and non-first seismic action was established, and fatigue damage energy was defined. In addition, damage model was introduced to assess the performance degradation of resilient column under first and non-first earthquake effects. The models were then verified by comparing prediction results with test results.