Experimental Study On Bond Performance Of Corroded Steel Bars And Concrete After High Temperature

Steel corrosion is the main cause of deterioration of reinforced concrete structure performance,and fire is a disaster with high frequency.Corroded reinforced concrete structures still need to withstand fire during service.The bond performance between steel and concrete is the basis for the analysis of reinforced concrete structure.The research on the bond performance between corroded steel and concrete after high temperature can provide a theoretical basis for the performance analysis of corroded reinforced concrete structures subjected to high temperature fire.Based on the experimental research,the paper proposes a bond-slip constitutive model of corroded steel and concrete after high temperature.The electrochemical accelerated corrosion test method is adopted to obtain the tensile test pieces with different degrees of corrosion by controlling the energization time.Due to the expansion and deformation of the corrosion products of the steel bars,the surrounding concrete generates the circumferential tensile stress,which causes the concrete cracks to appear and the crack directions The surface of the concrete is extended.The variation of the rust expansion crack of the concrete specimens with different degrees of corrosion is observed.The high temperature heating test of the drawn specimens at different temperatures is carried out by using the high temperature furnace to observe the changes of the appearance and structural properties of the concrete after different temperatures.And analyzed the reasons for the changes.The bond-slip-curve of corroded steel and concrete after high temperature is obtained by drawing test.The test results show that the bond strength between steel and concrete is very closely related to the corrosion rate of steel,the temperature experienced and the thickness of steel protective layer.As the bond strength increases with the increase of the corrosion rate of the steel bar,the bond strength first increases and then decreases.As the bond strength increases with temperature,the bond strength first increases and then decreases.The thickness of the protective layer becomes large,and the bond strength increases accordingly.The variation of the peak slip of the bond-slip curve of steel bars and concrete is similar to the change law of bond strength with the corrosion rate.However,for the corrugated drawing specimens,the splitting failure occurs when the temperature is high,and the peak slip changes.Not obvious.Summarize and analyze the existing reinforced concrete bond-slip model,establish the bond-slip relationship model after high temperature;consider the influence of steel corrosion and temperature on the bond strength,introduce the corrosion influence coefficient and temperature influence coefficient,and based onthe test results The calculation method of the influence coefficient is given by the least squares statistical analysis.The least square method is used to calculate the model parameters including peak slip,residual bond strength and curve rise segment parameter ? based on the experimental results.The test results were compared and verified by the proposed bond-slip model.Finally,the bond-slip model was used to evaluate the structural performance after fire.