Refinement simulation of bond-slip performance of deformed reinforced concrete exposed to fire: Parametric analysis

The refined numerical simulation method was used to study the influences of the concrete cover and the diameter of the rebar on the bond-slip properties of deformed reinforced concrete under two fire scenarios. The feasibility and rationality of the refined simulation method were verified by comparison with the experimental results. Subsequently, the influences of the concrete protective layer thickness and the diameter of the rebar on specimen failure pattern, bond failure mechanism, bond-slip curve, and the distribution of the stress and strain for the steel were investigated. The effects of parameters on ultimate, residual bond strength and ultimate slip were mainly discussed. The results show that the failure pattern of the specimen exposure to heat conditions changes from concrete splitting to steel bar pull-out as the concrete cover thickness increases; the shape of the bond-slip curve was affected by the concrete cover thickness, regardless of the fire scenario, rebar diameter and the target temperature. As the rebar diameter increased, the bond strength at high temperatures and after cooling down decreased when the specimen experienced the same temperature. Finally, the formulation for the bond strength and slip at high temperatures and after cooling down was suggested by comparing with the experimental and calculated results, which can take into account the thickness of the concrete protection layer, the diameter of the reinforcement bar, the fire scenario and the temperature.