| Among the many factors affecting the durability of reinforced concrete structures,steel corrosion is the main cause.Corrosion of steel bars in concrete will reduce the bond performance between steel bars and concrete,affecting the applicability and bearing capacity of reinforced concrete structures.During the service process,the reinforced concrete structure itself will produce cracks due to shrinkage and creep,and the effect of continuous load will gradually increase the number of cracks and the width of cracks.Oxygen,moisture and other corrosive substances in the surrounding environment will enter the concrete structure through cracks,accelerate the corrosion of steel bars and further reduce the bearing capacity of the structure.Up to now,domestic and foreign scholars have carried out a lot of experiments on the effect of continuous load and steel corrosion on reinforced concrete structures.However,for the analysis of reinforced concrete structures with continuous load and corrosion,most scholars take reinforced concrete specimens without cracks as the object.Pilot studies have failed to take into account the fact that most of the reinforced concrete structures in the actual project have initial cracks.In this paper,15 reinforced concrete beams with cracks in the bonding section were selected,and the method of accelerating corrosion with applied current overlay was used to test the combined effects of continuous load and electric accelerated corrosion.The main research contents are as follows:(1)By recording the initial slip amount between the reinforced concrete and the variation of the time-varying slip amount with the energization time,the total slip amount,initial slip amount and time-varying slip amount between the reinforced concrete were obtained with time.The relationship between the changes and the variation of the slip amount with time is analyzed.The results show that after the load is applied to the beam specimen,the slip amount increases obviously and the slope of the curve is large.The increasing trend of the slip amount gradually slows down with the increase of the energization time.As the value tends to be more stable,the slope of the curve also becomes smaller..(2)The bending test of the beam specimens subjected to continuous load and accelerated corrosion is carried out,and the relationship between the slip and bond stress of reinforced concrete is obtained.The bond strength and longitudinal reinforcement of the beam specimen are analyzed.The relationship between the theoretical corrosion rate and the holding level is found,and it is found in the test that the slip amount of the loading end of the beam type test piece is generally larger than the free end slip amount.(3)Using non-destructive testing and damage detection methods,the concrete beam test specimens subjected to continuous load and accelerated corrosion are rusted.Using the steel corrosion detector,it was detected that the severely corroded areas were concentrated in the middle and lower parts of the left and right half beams of the beam test piece,which basically coincided with the position of the longitudinal reinforcement bond area in the beam type test piece.According to the damage detection method,a small amount of uneven reddish-brown rust on the surface of the longitudinal section of the beam specimen was observed,and the degree of uneven rust was obvious,which was close to the rusting process in the natural environment.(4)Crack the beam test piece to take out the longitudinal ribs in the concrete,cut the longitudinal rib bonding section and pickle the weighing to measure the actual rust rate.The test results show that the actual corrosion rate of the longitudinal reinforcement zone is generally smaller than the theoretical corrosion rate.Under the same theoretical corrosion rate design value and the same power-on time,the longitudinal reinforcement bond increases with the continuous load grade on the beam test piece.The actual corrosion rate and rust efficiency of the section also increase. |
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