In order to study the influence of the reinforcement ratio on fracture parameters such as the fracture toughness

the effective crack length and the effect of the reinforcing bar on crack propagation of concrete

through the theoretical analysis and fracture failure characteristics of reinforced concrete

the double-K fracture criterion of reinforced concrete was established

and on this basis

12 three-point bending specimens divided into 3 groups and with different reinforcement ratios were designed and constructed

the curves of load-crack mouth displacement（P-CMOD） were measured

The influence of the reinforcement ratios on fracture performance of reinforced concrete three point bending beam specimens were researched.The results show that crack propagation process of reinforced concrete can be described by double-K fracture criterion.The values of initiation fracture toughness is independent of reinforcement ratio and can be regarded as material constant.The unstable fracture toughness slowly increases with the increase of reinforcement ratio.Exsistence of the reinforcement may restrain faily the propagation of the crack.