Eight concrete beams reinforced with 500MPa steel bars and four reinforced with 400MPa ultrafine grain steel bars were tested under twopoint symmetrical concentrated static loading to observe the details of crack pattern development on these beams and investigate their cracking characteristics. It was shown that the cracking behavior of the beams with highstrength bars was essentially similar to that of common RC flexural members

whereas the computed crack widths using the formula adopted in the Code for Design of Concrete Structures GB 500102002 exceeded that of the experiment under the normal service. Furthermore

the formulas for crack spacing and crack width specified in GB 500102002 were evaluated through the experimental results and previous studies of sixtyseven concrete beams reinforced with highstrength bars. On the basis of the calculation model in GB 500102002

revised formulas for crack spacing and crack width were proposed. The values calculated by revised formulas were in good agreement with the test results.