Research On Shear Behavior Of Corroded RC Beams

Abstract:Corrosion of reinforcement is one of the main factors which affect the durability of the reinforced concrete (RC) structures in service. As the corrosion rate of steel propagates, it will cause the cracking of the concrete cover, the deterioration of the bond between the reinforcement and concrete, the decrease of the cross-section of the steel reinforcement and the reduction of the shear capacity of the structures. For the vast majority of concrete beam, the stirrup is in the lateral of the longitudinal reinforcement and the concrete cover of it is much thinner compared with the later. Therefore, the corrosion of stirrup will be earlier and worse than the corrosion of longitudinal reinforcement. Failure modes of concrete will change from the bending failure to shear failure when the corrosion rate increase. Shear failure is brittle failure, which will injure the performance of structures. So it is vital to discuss the shear behavior of corroded RC beams especially the previous studies is not enough. Research work in this paper can be introduced as:(1) A static load experimental study of24corroded RC beams was conducted. The result shows that:the characteristics of corroded RC beams shear failure is basically same vary in different strength grade of concrete, namely small deflection, no obvious signs, quickly unload and obvious brittleness; the deflection size of the corroded RC beams is not closely related with the strength of concrete but with the component members span, that is to say the larger the members span, the greater the deflection at failure.(2)302corroded stirrups subjected to tensile load were tested. The result indicates that:the ductility of corroded stirrups decreases sharply; the yield strength and ultimate strength of stirrup are almost equal, while the stirrup section corrosion rate exceeds15%; for the same grade of steel, the effect of corrosion on small diameter steel is greater, while the grades of steel is change, the impact of corrosion on the high grade steel is more serious.(3) Existing steel corrosion ratio calculation and measurement methods are summarized. The reinforcement general corrosion is an ideal state, meanwhile it is difficult to ensure the accuracy of localized pitting corrosion. Quality corrosion ratio has a direct relationship with the length taken from the specimen, while the area corrosion ratio is directly related to the position taken from the specimen. However, the length and location to measure the corrosion ratio are not clearly defined. In view of this, a method that can intuitively measure the corrosion of the longitudinal reinforcement was proposed in this paper.(4) A database of previous shear test about corroded reinforced concrete beam was established, and the applicability of existing computational models was verified by applying it. A new calculation model was put forward according to reinforced concrete beams shear calculation formula of the European standard and considering the influence of longitudinal reinforcement and stirrup corrosion on the capacity performance. Predictions of the new model are closer to the test result comparing with previous models.