Experimental Study On Bond Behavior Of Corroded Reinforced Concrete Under Loading

The reliability of the engineering structure depends on whether it is safe,applicable and durable.The research of safety and application is relatively perfect.But the problem of structural durability is increasing and the research of durability has become a hot spot.Corrosion is the main factor for the deterioration of the durability of concrete structures.The structure of the actual project is in the state of stress,so the influence of corrosion on the bond behavior of reinforced concrete beams is studied.Research contents of this paper as follows:(1)The research method of this test is beam bonding,considering the bond behavior of corroded reinforced concrete beam under different load level,design and product 40 beams,set the influencing factors: holding levels,the corrosion rates of steel,the concrete strength grades,reinforced types.Analysis the differences of corrosion under loading on the bond strength of reinforced concrete beam.(2)In this paper,design a set of load corrosion loading device to accelerate the corrosion of reinforcing steel bars self improvement.Two point concentrated load is destroyed,and automatic acquisition system is used to collect and record test data continuously.Based on the test data,the bond slip curves were made and compared.The influence degree of different factors on the corrosion of steel bar was analyzed,and the effect of rust on the bond performance of reinforced concrete beams was also analyzed.(3)The results show that under the same condition,the effect of holding on the corrosion rate of steel bars is not significant,and the holding state is not the main cause of corrosion,but the holding level has an obvious influence on the corrosion form of steel bar.Excluding the influence of corrosion rate,the holding level is the best to enhance bond strength in the range of 40%-50%.The corrosion rate has a strong effect on the bonding between reinforced concrete in a certain range.The corrosion rate is within the range of 4%,and the load will increase with the increaseof corrosion rate.Beyond this limit,the bearing capacity will decrease with the increase of corrosion rate.For ribbed steel bars,the corrosion threshold is 5%.The surface morphology of the beam also has a certain degree of corrosion,such as pits,holes,moisture can promote the corrosion of steel bar.The more serious corrosion is,the greater the change of steel surface morphology,the greater the fluctuation of stress slip curve.The degree of corrosion is the main factor of the change of bond properties,and the small change has greater disturbance to it,but the higher the strength,the influence of the change of corrosion rate on the bond properties of the members gradually weaken.(4)According to the influence of the bearing grade and the corrosion rate of steel bar on the bond strength and the slip of the free end of the steel bar,the piecewise bond slip constitutive model is chosen to fit the bond slip constitutive relation of the corroded reinforced concrete under the regression holding,and the consistency is better.