Research On Mechnical Behavior Of Concrete Members Due To Reinforcement Corrosion

Steel corrosion is one of the most crucial and influential factors on the durability of the concrete members, which not only decreases the effective area and mechanical property of steel bar itself, but also leads to the cracking of the concrete cover and the retrogression of bond capacity between steel bar and concrete, and finally results into a series of degrading behaviors, such as: the failure mode changing, carrying capacity declining, ductility reducing and so on. Therefore, it is very necessary to do some research on the mechanical behavior of concrete members due to reinforcement corrosion so as to guarantee the security of the concrete structure during services period.There are two parts involved in this paper:1. Based on the experimental researches on the21concrete beams with corrosion steel, in order to reveal the impact mechanism to the degradation process of mechanical behavior of concrete beam with the development of steel corrosion,the influences of the steel corrosion on failure mode and carrying capacity of the concrete beams were the main focused research contents;2. Based on the experimental researches on15hollow hinge joints with corrosion steel, the influences of the damage caused by steel corrosion on cooperative working performances of hollow slabs was the main focused research content. According to the researches, the relationship of the hinge joint deterioration and hollow slabs cooperative working performances was studied in the paper.The main achievements as follows:1. Based on the basic theory of concrete beams, two computational formulas were established to respectively calculate the bending and the shearing capacity considering two different step situations:longitudinal steels bond slippage and longitudinal steels not, and the possible failure modes of concrete beams with the development of the stirrup and longitudinal steel corrosion were also discussed;2. Four groups of experimental concrete beams with two kinds of shear span ratio and stirrup ratio were designed in this paper. Before the static load test, the DC power method was used to accelerate the corrosion of and longitudinal stirrup steels. According to the static load test results, with the corrosion development of the longitudinal and stirrup steels, it was found that:①the bending failure beam will transform to compression-shearing failure and later bond-compression-shearing failure.②the compression-shearing failure beam will transform to bond-compression-shearing failure;3. From the experiment results, it was known that the development of steel corrosion would induce the concrete beams to different failure modes:①When the longitudinal steel corrosion was not serious, with the increasing of the stirrup corrosion, the beam’s shearing capacity would be less than the bending capacity, so the concrete beam would transform from bending failure to compression-shearing failure;②With the development of the steel corrosion, especially when the longitudinal steel corrosion was serious, the bond performance between the corrosive longitudinal steels and the concrete would be the controlling factor for the failure mode, so the concrete beam would transform from compression-shearing failure to bond-compression-shearing failure;4. The results show that:when the bond strength between the steel bar and concrete was able to guarantee the collaborative work of the corrosive steels and the concrete, the concrete beam would occur material strength failure; otherwise, which would occur bond failure;5. Through analysis and researches, the conditions for the transformation of the failure mode and the failure regulation of the concrete beam due to longitudinal and stirrup steel corrosion were established;6. According to the research results, the bigger the diameter of the longitudinal steel is or the lower the concrete strength is, the more probably the cohesion failure would occur. According to this, the enabled limit for the cracking width of the concrete cover due to steel corrosion was suggestion;7. According to the analysis for the deformation feature of the experimental beams, the mid-span deflections were calculated. After comparison with the experimental data, the validity of the conclusion was better certified;8. There are also some advices for current JTG D62-2004and JTJ267-98standard:For the concrete beams service in severe conditions, the minimum steel quantity in JTG D62-2004is appropriately proper, while the steel quantity in JTJ267-98would need to increase;9. According to the hinge joint damage caused by steel corrosion, based on damage mechanics theory, cooperative working coefficient (?) was defined to reflect the deflection differences of the two hollow slabs on both sides of the hinge joint. Reference to the relevant code, reasonable range of (p was suggested;10. According to factor analysis approach, the formula of (?)p was established by regression method. After extensive validation, it was believed that the formula can reveal influential degree that the hinge joint performance changing on cooperative working performance of the hollow slabs;11. According to the time-varying regulation of the steel corrosion on hinged joint, the time-varying evaluation model of the cooperative working performance of the hollow slabs was established. Then the durability evaluation of the deep, medium and shallow hinged joints was carried out in this paper.