Experimental Study On Mechanical Behavior Of Diagonal Section Of Reinforced Concrete Beams With HRB500 Stirrups

HRB500 is a new type steel bar which has many merits, such as high-strength and strong ductility. This kind of steel bars has been used prevalently in foreign countries. It will be taken in Code for design of concrete structures which is revising. When HRB500 steel bars used as stirrup, the reinforced concrete beam may appear so oversized diagonal crack that it can't satisfy the engineering requirements for applicability and durability. It has been taken to a topic for study by the admini- strative committee of Code for design of concrete structures in 2004, then they organized correlated organizations to research. So we participate in this study.Base on the shear behavior experiment of 16 simple-supported reinforced concrete of rectangle section with high-strength stirrups subjected to concentrated loads, the thesis studies the diagonal cracking behavior, opening of diagonal crack, failure model and deformation characteristics of these beams. The thesis especially explores effects of shear span-to-depth ratio, stirrup reinforcement ratio , concrete strength on the diagonal cracking load , opening of diagonal crack and shear bearing capacity.The thesis proposed a new kind of calculation method of the Softened Strut-and-Tie Truss, this model takes account of the soft phenomenon of concrete subjected biaxial stress, tied arch effect and the nonuniform stress in stirrup along the shear span. Based on the shear test data of our study and others, the thesis proposed a formula on calculating the ultimate shear capacity of RC beam. The calculation of derived formula originate from the model conformed fine to the experiment data, it could use to predict the ultimate shear capacity.The thesis derived the practical formula of diagonal crack width from the experiment data of crack, Furthermore, the thesis quoted various data of domestic and abroad experiment to verify the universal of the formula. As result, the calculation results coincide well with the actual case of the crack to a certain extent, so we could quantify to calculate the width of the diagonal crack with the proposed formula.Finally, from the point of RC beams with HRB500 stirrups would satisfy the requirements of serviceability limit states of the Code, the thesis proposed the characteristic value of this high strength bars when design as stirrups, to a certain extent, it will make some references to the studies of the Code.