Research On Bending Reliability Of PC Continuous Box Girder Bridge Strengthened By External Prestressed Tendon

PC continuous box girder bridges need to be maintained and reinforced due to the bending load capacity decreased during long-term operation.The reliability of bridge structure is one of the important indexes to evaluate the safety of bridge structure and the effectiveness of bridge reinforcement.In this paper,the bending reliability index is used to evaluate the reinforcement effect of PC continuous box girder bridge which is strengthened by externally prestressed tendons,and on this basis,the influence of time variation on reliability index was also considered.Meanwhile,this paper presents a safety evaluation procedure of PC continuous box girder bridge based on dynamic bending reliability index,which provides a scientific basis for bridge reinforcement technology and safety assessment.The main contribution of the paper is composed of the following three parts:The probabilistic statistical model of vehicle load effect based on existing bridge is updated and evaluated.To modify the load distribution of the vehicle load,this paper introduced the correction factor of vehicle load effect into the unified standard for reliability design by investigating the actual traffic volume of the bridge.This paper redefined the maximum load distribution of existing bridge load effect by adjusting the evaluation base period.This paper proposed an updated probability model of vehicle load effect whicih considered the correction factor of vehicle load effect and the evaluation base period.It is found that the proposed model can effectively simulate the actual operation of the bridge.This paper analyzed the reinforcement effect of PC continuous box girder bridge strengthened by external prestressing bars based on reliability theory.Aiming at the PC continuous box girder bridge strengthened by external prestressed tendon,the probability model of bending load capacity before and after reinforcement is established by the means of analyzing the resistance function of the box section before and after reinforcement.The Monte Carlo method was used to simulate the statistical parameters of resistance.Finally,the mapping transformation method was used to calculate the reliability.It is shown that the variation law of flexural reliability of different members after reinforcement can effectively reflect the impact of reinforcement on different span bridges and vehicle load lift.This paper accomplished the safety assessment of PC continuous box girder bridges with reinforcement considering their dynamic bending reliability.This paper analyzed the factors affecting the resistance degradation of PC continuous box girder bridge,and it also improved the concrete carbonization depth model and the prestressed reinforcement section corrosion rate model.The decay resistance model of PC continuous box girder was established by dividing the bridge operation life into four stages.The bending dynamic reliability evaluation process was established based on the dynamic reliability.In this part,the evaluation process of dynamic bending reliability in this paper was applied to a real PC continuous box girder bridge reinforced by external prestressing tendons in Shenzhen,China.Safety assessment and life prediction of the bridge are accurately evaluated through our proposed method.