| In the long-term service of prestressed concrete continuous box-girder bridge,the material property of the bridge has been declined with the time because it not only bears external forces such as vehicle load,vehicle impact force,crowd load,and wind load,but may be eroded by the surrounding environment and chemicals.Moreover,the structural members of the bridge are going to be damaged to different degrees with the extended operation period.The continuous accumulation of these damages will eventually affect the normal operation of the bridge and may even cause safety accidents.Therefore,it not only reduces the potential safety hazards of the bridge,but also brings economic benefits by carrying out a scientific and reasonable reliability analysis and remaining life prediction of the existing bridge structure,as well as offering the reliability level of the bridge within its design reference period,so as to take corresponding maintenance and reinforcement measures in time.The paper takes the reliability and remaining service life of the prestressed concrete continuous box-girder bridge as the research objects.Then on the basis of previous research,the paper analyzes the time-varying model of factors that affect the bridge reliability such as the bridge weight,vehicle load,component geometry and material property.In addition,the paper compares the time-varying probabilistic models of several sets of material property,and then proposes their respective applicable environments.Meanwhile,attention is paid to the correction of statistical parameters of material property considering a certain deviation between the bridge detection data.And the prediction value of the time-varying probabilistic model is also took into account.Afterwards,a load probabilistic model and a resistance probabilistic model are constructed for the prestressed concrete continuous box-girder bridge.Combined with an engineering case,the time-varying statistical parameters of bridge’s dead load,vehicle load and bending resistance of the normal section are obtained according to the above probabilistic model.With the obtained data,the paper conducts the flexural reliability analysis and the prediction of the remaining life of the bridge,thereby showing the time-varying regularity of the reliability of the prestressed concrete continuous box-girder bridge.The paper is of significance and innovation meaning of engineering guidance because it is conducive to providing references for the improvement of the reliability of the prestressed concrete continuous box-girder bridge and the extension of its remaining life,as well as the improvement of the reliability evaluation method of the prestressed concrete bridge in service.The main research contents and results are shown as follows:(1)Based on the basic principle of JC method,a program interface for calculating the reliability index is developed by Matlab.(2)Based on finite element model,the probabilistic model of bridge load and vehicle load is established.Established the probabilistic model of five factors,namely concrete strength,cross-sectional area and yield strength of steel bars,cross-sectional area and yield strength of prestressed tendons,and studied the time-varying law of their statistical parameters.In this paper,attention is paid to the correction of statistical parameters of material property considering a certain deviation between the detection data and the predicted value of the time-varying probabilistic model.These allow the resistance attenuation model to reflect the actual situation of the project more accurately.On this basis,a time-varying probabilistic model of the normal section bending resistance is established for the prestressed concrete continuous box-girder bridge influenced by various factors.(3)Exemplified by a prestressed concrete continuous box-girder bridge in service,the paper evaluates its flexural reliability and predicts its remaining life.The Midas Civil is applied to set up a finite element model.Based on the time-varying reliability theory,calculated the statistical parameters of the time-varying random variables of the main bridge.Based on the above probabilistic model for the dead load and vehicle load and the probabilistic model for the bending resistance of the normal section of the prestressed concrete continuous box-girder bridge at different stages,the time-varying statistical parameters of the dead load,live load and comprehensive resistance are obtained.The time-varying laws of reliability index of the normal section bending resistance of the bridge structural member are obtained through the reliable index calculation program compiled with Matlab.The remaining life of the bridge is predicted by comparing the obtained data with the target reliability index.According to the results,it can be found that the flexural reliability index of the bridge is only affected by the changes in concrete strength and load effects during the initial operation of the bridge,and the reliability index fluctuates less.The reliability index began to drop sharply when the steel bar corroded.In addition,the reliability index goes in a downward trend along with the extended operation time of the bridge.Since prestressed steel is more sensitive to corrosion,its mechanical properties decrease with increasing corrosion rate.The analysis shows that the corrosion rate of prestressed tendons plays a major role in the reliability of prestressed concrete continuous box-girder bridges. |
