The bond-slip behavior of H-shaped steel embedded in UHPC under reversed cyclic loading

To investigate the bond-slip behavior of the interface between H-shaped steel and ultra-high performance concrete (UHPC) under reversed cyclic loading, 18 steel-UHPC and 6 steel-NC composite specimens were fabricated and subjected to both reversed cyclic and monotonic loading tests. Key parameters including concrete strength, steel fiber volume fraction, embedded length of the steel section, and loading scheme were examined. The results indicate that, under reversed cyclic loading, the bond strength of the steel-UHPC composites decreased by 7 %–15 %, while the residual bond strength decreased by 16 %–57 % compared to monotonic loading. For both loading schemes, bond strength slightly decreases with an increase in embedded length but can be significantly enhanced by increasing the steel fiber volume fraction, which also improves residual bond strength and energy dissipation under reversed cyclic loading. Additionally, bond strength increases with higher concrete strength. Finally, a damage index D derived from the bond stress-slip hysteresis curves was used to represent bond degradation under reversed cyclic loads, and a constitutive model to predict the bond-slip behavior of the steel-UHPC interface under reversed cyclic load was presented.