Hysteresis behavior of RC columns with steel angle ends under various levels of axial load

Bolting steel angles at the bottom ends of columns provides a rapid and efficient method for repairing damaged structures, while also offering a viable approach to restore their potential bearing capacity. To validate the suitability of specific strengthening strategies, particularly the utilization of bolted steel angles, three reinforced concrete frame specimens were subjected to hysteresis testing. These specimens all featured RC columns strengthened with steel angle ends. Additionally, one control specimen without steel angle ends was included in the testing. The hysteresis effects of bolting steel angles were discussed in terms of typical failure mode, hysteresis and skeleton curves, stiffness degradation and energy dissipation. The experimental results revealed that the three specimens that had bolted steel angles exhibited ductile failure behavior. Through analysis of hysteresis and skeleton curves, it was observed that the frame demonstrated distinct plasticity, maintaining sufficient load-bearing capacity even after yielding and exhibiting superior displacement ductility performance. Considering equivalent viscous damping, the energy dissipation capacity of the RC frame increased linearly with drift and remained largely unaffected by structural damage. Therefore, bolting steel angles at specified cross-sections proved to be a viable technique for structural repair and restoration.