Bond-Slip Behavior between Deformed Rebar and Concrete at Cryogenic Temperatures

Abstract

The bond behavior between steel bar and concrete is greatly affected by the properties of the concrete material and rebar. Compared with ambient temperatures, the mechanical characteristics of concrete material and rebar vary greatly at cryogenic temperatures in cold regions. To investigate the bond behavior at cryogenic temperatures, pull-out specimens were simulated considering the surface characteristic of deformed rebar and the cryogenic temperature effects on the mechanical properties of materials. In the model, the surface-to-surface contact interactions were adopted between the interacting sections. The studied parameters include three bond lengths (48, 80, and 112 mm) and a temperature range from 20°C to −120°C. The failure process at cryogenic temperatures, final failure modes, bond strengths, and slip were investigated, and the related influencing mechanism was analyzed. The numerical results demonstrated that the increasing bond length changes the failure pattern from splitting failure to pulling-out failure and reduces the bond strength. The bond behavior is significantly affected by cryogenic temperatures due to the enhanced strength and brittleness of materials. The damage of concrete surface in bonding area at cryogenic temperatures is more serious than that at ambient temperature, but the final failure mode is consistent. The bond strength and bond stiffness are enhanced at cryogenic temperatures. As the temperature dropped from 20°C to −120°C, the ultimate bond strength improved linearly by 11.8%, whereas the residual bond strength and ultimate slip decreased linearly by 51.3% and 15.7%, respectively. According to the numerical results, a bond-slip model was established to predict the bond behavior at cryogenic temperatures.