Reliability Analysis Of Prestressed Concrete Bridges With Chloride Corrosion

As an affordable high-strength building material,prestressed concrete has been constantly improving its position in the construction project.Prestressed concrete girder bridges also account for a large proportion of modern buildings.In recent years,however,the prestressed concrete girder bridges have undergone resistance deterioration and even premature failure due to corrosion damage.In particular,prestressed concrete structures that are rich in chloride ions will suffer more severe corrosion and lose reliability.This is due to the chloride ion inside of the structure will act as a catalyst to accelerate the corrosion process.In order to maintain the reliability and durability of the structure,the reliability of prestressed girder bridge under the corrosion of chlorine salt was analyzed.A series of studies were conducted on the corrosion of prestressed concrete in chloride ion environment.The main contents are as follows:(1)The salt spray test in the state of compressive stress was carried out,and the chloride ion content of different water-cement ratios and different depths in the state of compressive stress was compared and analyzed.The chloride ion transport theory is described,and the influence of different factors on the diffusion of chloride ions is described.The existing researches on chloride ion diffusion model under stress are summarized.The basic model of chloride diffusion was modified,and the experimental data was used to validate the modified model.Corresponding corrosion initiation time models were deduced from the modified model,and the results under different stresses were compared.(2)The corrosion mechanism and fracture morphology of prestressed steel strands are briefly introduced.The corrosion area calculation methods for steel bars and steel strands under uniform corrosion and pitting corrosion are listed separately.Because the steel strand is made of seven steel wires,its special section geometry has complicated the calculation of point erosion area.Nowadays,there is no clear research on the calculation of the pitting area of steel strands.In this paper,three kinds of simulations of the pitting path of steel strands are performed,and the characteristics of the three simulation methods are illustrated.Afterwards,a simplification method was proposed to simplify the complexity of the simulation,and the accuracy of the simulation was verified by comparing the calculated values with experimental data.The resistance model of the steel strand is deduced and the effective value range of resistance is planned.(3)A brief description of the calculation methods for structural reliability and reliability.Taking a certain bridge as the instance background,the MATLAB program was programmed to calculate the resistance of the bridge,and the failure probability of the bridge in 100 years is obtained by using Monte-Carlo method.The effects of time-varying concrete strength,different corrosion current density,different protective layer thickness,and different marine environments on the failure probability of prestressed concrete girder bridges were considered separately.