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 fy/ft indicating the ratio of reinforcement yield strength to concrete tensile strength were investigated quantitatively. The results indicate that las/d (the ratio of the stable development length to bar diameter) increases linearly with fy/ft increase

but gradually decreases with the increasing c/d. The formula of las/d for fy/ft and c/d was established

and the potential influence factors of the bond stress fb were evaluated

including reinforcement yield strength

concrete tensile strength

the relative concrete cover and the embedment length lat. The results indicate that c/d is the only factor to constrain the parameter fb/fy to be varied with the index lat/las. A reliable calculation formula of the fb/fy for c/d and lat/las was proposed.