The Research On Shear Capacity Of Corroded Stirrups RC Beams With Diagonal Reinforcement

Steel corrosion is one of the most common issues for concrete weakness used in bridges, and the most important factor to cause the destruction of concrete. The corrosion will result in the reduction of steels'interface area, degradation of mechanical properties, the cracking of protecting cover, the reduction of bearing capacity between steels and concrete and the reduction of the bearing capacity of bridge. At present, the research on bearing capacity of intersection of reinforced concrete has been carried out widely both at home and abroad while the research on the shear performance of inclined intersection is less. Especially, the research on diagonal reinforcement or bent steel of corroded stirrups beams is almost blank in this field. Because of the short diameter of stirrups and the thin protecting concrete, stirrups'corrosion is often in more serious situation and delivers greater effect on the shearing of inclined intersection.In order to better assess the RC bridge with shear properties of diagonal reinforcement, based on the combination of the project of national natural science funds "both shear performance degradation model of existing RC bridge and reliability research (50878031)", this article makes a research on beam and six corroded stirrups RC beams with diagonal reinforcement. With stirrups carried on the electrochemical corrosion, shear performance test of inclined intersection of all the beams finished, main research work can be drawn as following:(1) Exploring the corrosion mechanism and its related factors and a comprehensive analyzing on the reinforced concrete structure.(2)An exploration and deep study on the shear properties of inclined intersection of corroded stirrups RC beams with diagonal reinforcement. In consideration different corrosion degree of stirrups of caused by the degradation of the mechanical properties, the test studies the development process of crack property and its failure process, deflection's variation and the strain distribution of steel and concrete. Some conclusions can be drawn as follows: in the same shear span, stirrups'corrosion does not affect the failure model of the beam; with the corrosion of stirrups increased, the cracking load decreased, critical loading capacity rises and descends consecutively. Stirrups'corrosion prolongs the time span of the critical cracking, but does not affect the emerging time of inclined cracking. (3) The shear capacity of corroded stirrups RC beams with diagonal reinforcement is researched on the basis of the modified compression field theory. With the existence of diagonal reinforcement, it is necessary to modify the stress equilibrium between the internal force equilibrium of concrete and the stress equilibrium among cracks. Combining the intersection analysis of pure shearing and pure bending state, a formula to calculate the internal force under bending and shearing is therefore obtained. Calculating process programmed, stirrups'rusting area and the yield strength is introduced to make a hypothesis and iterative. Finally, the shear capacity of corroded stirrups RC beams is calculated and analyzed and the shear formulas of concrete and highway prestressed bridge regulatory norms are introduced. Considering the damaging impact of stirrups'corrosion on concrete intersection and the linearization of bond strength and pin bolt of longitudinal reinforcement, for correction coefficient linear regression, a formula of shear capacity resulted from corroded stirrups is obtained. Comparing the results with the experimental data, the two series figures are in agreement with each other, showing that the modified compression field theory is applicable on corroded stirrups RC beams with diagonal reinforcement.