Experimental Study On Mechanical Properties Of RC Members With 600MPa Steel Bars

The hot-rolled reinforced bars with a specified yield strength of 600MPa is a new type of steel bars, which has many merits, such as high-strength and strong ductility. China started research the 600MPa steel bars later than many other conutries, lacking related test datas and engineering application. In order to popularize this new kind of steel bars in the engineering field of our country, experiments on flexural performance and shear behavior of beams. Seismic performance of beams and columns, and bond-anchorage properties have been conducted in this paper. Some conclutions have been drawn after a comprehensive analysis of the main mechanical properties of concrete members reinforced with 600MPa steel bars, and it mainly includes:A flexural performance test under concentrated loading of four concrete beams reinforced with 600MPa steel bars and one reinforced with 400MPa steel bars was conducted. The result shows that the stress distribution along the section of beams with 600MPa steel bars is basically in accordance with the plane section assumption; the failure mode of beams with 600MPa steel bars is the same as the common RC flexural members’, and the formula in the existing code are shown to be suitable for calculating flexural strength of the beams; there is enough security reserves when the design value of tensile strength of 600MPa steel bars takes 500MPa. Under the state of serviceability, the calculated values of average crack spacing of beams with 600MPa steel bars coincided with the test well; the calculated value of the maximum crack width is larger than the test value, and the possible reasons were analyzed. However, the calculated values of deflection of beams with 600MPa steel bars are smaller than the test values, analyzing the reasons and the suggestion is that it can be multiplied by an expansion coefficient 1.25) to correct the calculating results.A shear behavior test under concentrated loading and uniformly distributed loading of four concrete beams reinforced with 600MPa stirrup and one reinforced with 400MPa stirrup was conducted. The result shows that the calculation formula of shear capacity given by the existing code has a large margin, which can ensure that the oblique cross section won’t damaged. There is great difference between the formula for calculating shear strength of the diagonal section given by standard GB50010-2010 and the counterpart in Europe and America codes.A seismic performance test under low cyclic loading of one beam reinforced with 600MPa steel bars, one with 400MPa and two columns reinforced with 600MPa steel bars, two with 400MPa was conducted. The result shows that the failure mode, bearing capacity, and deformability of both beams are similar, but the beams with 600MPa steel bars has less energy dissipation than the one with 400MPa steel bars. On the condition that same axial compression ratio, bearing capacity and energy dissipation of all columns are similar, but the columns with 600MPa steel bars have better deformability than the ones with 400MPa steel bars.A pull-out test of 18 specimens with different steel bar diameters and different concrete strength was conducted to verify the anchorage performance of 600MPa steel bars. The result shows that the formula for calculating anchorage length in excisting structure code can be used for 600MPa steel bars, and there is enough security reserves. Compared with the American Standard, the calculation of anchorage length is smaller in Chinese structure code.