Research On Time-variant Reliability Analysis Of Stay Cables Under Corrosive Environment And Optimization Of Maintenance Strategy

Cable-stayed bridges have been widely used due to the characteristics of beautiful structure and spanning capacity,and as the main load bearing component of cable-stayed bridges,the performance of the stay cable has a significant role on the safety of the whole structure.However,its service environment is rather complex due to the multiple effects of long-term traffic loads and natural environment,which leads to the performance will be continuously degraded and threaten the structural safety seriously.Therefore,it is important to establish the scientific and effective maintenance strategy to ensure the service safety of stay cables.This paper discusses the optimization of the maintenance strategy of the cable from the viewpoint of the safety performance and economic cost,based on the reliability index of the cable under corrosive environment,which is mainly as follows:(1)The time varying reliability of the cable in the corrosive environment is analyzed model.According to the corrosion deterioration regularity of cable wires in each stage,combined with the research about the corrosion distributions of different wires on the same cross-section,the corrosion distributions of different wires on the cross-section were quantified and simulated differently.The cross-sectional loss area of corrosion damage of each steel wire is calculated,and the effective cross-sectional area reduction laws of the cable under environmental corrosion are obtained.The effective cross-sectional area loss ratio is used to characterize the resistance degradation of the stay cable,and the time-varying reliability of the case stay cable is calculated to provide the safety performance index basis for the establishment of the maintenance strategy model.(2)The combined maintenance strategy model of the stay cable is established.Based on the preventive maintenance and essential maintenance methods,integrated the safety performance index and maintenance cost,with the objective of minimum cumulative failure probability and maintenance cost simultaneously for the whole service life of the stay cable,the maintenance strategy model of the case stay cable is optimized and analyzed by the nondominated ranking genetic algorithm and the decision method of relative weighted distance with the time of preventive maintenance as the design variable under the constraint of satisfying the reliability index,the results show that the optimal compromise maintenance scheme obtained by using the combined maintenance strategy takes into account the safety performance of the structure as well as the economic value compared to using only the essential maintenance actions.(3)An opportunity maintenance strategy model for the stay cable system is established.For the maintenance of the stay cable system composed of multi cables,the idea of opportunity maintenance is introduced,the combined maintenance scheme for the single stay cable is solved with the cumulative failure probability and the total maintenance cost of the system composed of multiple stay cables as the optimization objectives.On this basis,under the premise of ensuring the safety performance of the stay cables,the non-dominated ranking genetic algorithm is used to optimize the opportunity maintenance time window with the objective of optimizing the total maintenance expense to obtain the optimal maintenance schedule for each cable member,and the established strategy model is verified and analyzed by solving the case cable-stayed bridge part as an example.The results show that ensuring the safety performance of the stay cable system,the adoption of an opportunistic maintenance strategy can realize the arrangement of maintenance programs for multiple cable members and save a lot of costs.