Study on eccentric compression performance of partially encased recycled concrete columns after high temperature

Abstract

Waste concrete has caused significant environmental damage. With the increasing use of recycled concrete in construction, its mechanical properties and performance under high-temperature conditions have become critical concerns. In fire situations, the eccentric behavior of recycled concrete columns wrapped with H-shaped steel sections may be significantly impaired, leading to a notable reduction in load-carrying capacity and structural stability. To mitigate this issue and conserve natural resources, this study investigates the application of recycled coarse aggregate in partially encased concrete (PEC) columns. The effects of temperature (T), recycled coarse aggregate replacement ratio (R), and eccentricity ratio (e/h) on the eccentric compressive behavior of partially encased recycled concrete (PERC) columns after high temperatures were examined. Six PERC columns were designed for this study, along with one PEC column as a control specimen. The experimental results indicate that PERC columns exhibit different failure modes, all ultimately failing due to concrete crushing and flange buckling. Exposure to high temperatures resulted in a maximum mass loss of 4.63 % in the specimens. Among the three variables, the eccentricity ratio (e/h) had the most significant impact on the ultimate load capacity and ductility of the PERC columns. Specifically, when the e/h ratio increased from 0 to 0.2, the ultimate load capacity of the column decreased by 43.9 %, while its ductility increased by 26.2%. Based on these findings, a new formula for predicting the ultimate load of PERC columns after high temperature is proposed, providing an effective reference for post-fire PERC column analysis.