Distribution regulation of the reinforcement force between bond and headed bars

Abstract:

Based on the bond stress-slip constitutive model between the reinforcement and concrete, a MATLAB program was coded to calculate the force of the headed bars, which was used to obtain the regulation of distribution between bond and headed bars of the high strength hot-roll reinforcement force, and it was validated by the pull-out tests of 120 reinforced concrete specimens. According to the simulation results, the combined effects of the relative concrete cover (the ratio of concrete cover c to bar diameter d) and an index f_y/f_t indicating the ratio of reinforcement yield strength to concrete tensile strength were investigated quantitatively. The results indicate that l_as/d (the ratio of the stable development length to bar diameter) increases linearly with f_y/f_t increase, but gradually decreases with the increasing c/d. The formula of l_as/d for f_y/f_t and c/d was established, and the potential influence factors of the bond stress f_b were evaluated, including reinforcement yield strength, concrete tensile strength, the relative concrete cover and the embedment length l_at. The results indicate that c/d is the only factor to constrain the parameter f_b/f_y to be varied with the index l_at/l_as. A reliable calculation formula of the f_b/f_y for c/d and l_at/l_as was proposed.