Analysis of Time-varying Reliability of Main Cables in Long-span Suspension Bridges Considering Material Performance Degradation
Steel wire corrosion is one of the main factors affecting the mechanical properties of the main cables of long-span suspension bridges.A time-varying reliability evaluation method for main cables considering material performance degradation is proposed to study the structural reliability degradation law of long-span suspension bridges under the consideration of main cable steel wire corrosion.Firstly,the main types of corrosion on steel wires and their corrosion mechanisms were derived and analyzed,and a material constitutive model considering steel wire corrosion was established.Secondly,a structural function considering the corrosion of the main cable steel wire was established based on reliability theory,and the corrosion level of the main beam was measured using the annual average resistance loss rate as an indicator.Finally,a BP neural network was used to fit the response surface of the suspension bridge structure,and a Monte Carlo sampling simulation method was used to design a time-varying reliability calculation method for the main cable under different corrosion levels.Taking a large-span suspension bridge as the engineering background,the degradation law of the time-varying reliability of the main cable under different corrosion levels and material sub coefficients was explored.The results show that BP neural network can accurately fit the mapping relationship between random variables and structural response of suspension bridges,and the average relative error of 10 validation set samples is only 1.47％;based on the annual average resistance loss rate,the faster the corrosion rate of the steel wire,the faster its reliability index deteriorates during its service life,and this rate increases with the increase of service life;the larger the value of the material sub coefficient,the higher the reliability index of the main cable structure under the same corrosion level.When considering the material performance degradation caused by the corrosion of the main cable steel wire,it is advisable to take a larger value for the design material sub coefficient.
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