Study On Flexural Bearing Capacity Of Existing Reinforced Concrete Bending Members

The RC(reinforced concrete)structure is generally regarded as being in ideal state when analysis of ultimate bearing capacity of RC structure conducted in the past.In fact,the actual state of the structure is inevitably accompanied with various degrees of defects and damage compared to the design state during construction and service period,these defects and damage may influence the working performance of the structure to some degree.However,the existing studys are usually concerned on the influence of some single kind of damage when analyse the ultimate bearing capacity of damaged RC structure,ignoring the complex coupling between the various types of damage.In this paper,by using finite element software,the flexural bearing capacity of RC bending members is analysed based on destructive testing of existing RC bending members.The main contents are as follows:(1)The current service state of existing RC bridges in our country is summarized and both domestic and foreign analysis methods to study the bearing properties of existing RC structure are systematically elaborated.(2)The cause and influence on bearing capacity of members of four common kinds of damage in existing RC bending members are detailedly introduced,such as steel corrosion,concrete cracking,concrete carbonization and section defect.And the simulation methods in finite element analysis are also proposed.(3)Based on the destructive testing of existing RC bending members,the material parameters and injury situation of test beams are obtained.Meanwhile,the constitutive relations of steel and concrete as well as the cohesive force between the two are proposed,then a discrete model of RC flexural member is presented based on the content above to discuss the independent effects of damage on the flexural capacity of RC flexural member.Then,finite models considering various kinds of damage are built,the results of finite calculation and testing are compared.(4)Based on the carbonated concrete constitutive relation and corrosion-induced inconsistent compatibility between steel and concrete,a calculation formula of normal section capacity of typical section form of RC flexural member coexisted with various damage is proposed by introducing the section reduction factor.The comparison between results of theoretical calculation and testing is conducted to verify the correctness of the values of proposed calculation formula.