Corrosion Fatigue Effect Analysis And Damage Identification Of High Strength Steel Wire And Parallel Steel Wire Cable

The cable and suspender represented by parallel steel wire cables are widely used in cable-stayed bridges and suspension bridges.The deck load is transmitted to the main cables and towers to ensure the safety of cable-supported bridges by suspenders and cables,which are the core stress components of cable-stayed bridges and suspension bridges.The design service life of parallel steel wire cables is 20 years,but many parallel steel wire cables are retired before reaching the service life.The investigation shows that the high strength steel wires in most parallel steel wire cables are broken due to corrosion fatigue.Firstly,based on the actual engineering situation,the failure mechanism of the single steel wire under the influence of corrosion,the alternate effect of corrosion fatigue and the coupling effect of corrosion fatigue were studied,respectively.Secondly,the failure mode of the parallel steel wire cable under the coupling effect of the tensile stress-bending stress-corrosion fatigue was researched based on the results of a single steel wire.Finally,the corrosion fatigue damage of bridges was evaluated by using the method of deep learning.In this dissertation,the corrosion fatigue failure mode and damage state of parallel steel wire cable was studied comprehensively and systematically utilizing the method of from small members to prominent members,from point research to surface research and from shallow research to deep analysis.The main contents of this dissertation are as follows:(1)The accelerated corrosion test of high-strength steel wire was carried out to study the performance degradation of high-strength steel wire during the process of designed life due to the corrosion.The distribution parameters of corrosion pits of high strength steel wire were analyzed using the statistical analysis method due to the randomness of the distribution and size of corrosion pits.The mechanical properties of steel wire under different corrosion degrees were tested by a universal testing machine.The stress-strain curves of steel wire under different corrosion degrees were obtained.The geometric model of random corrosion of steel wire and material model under different corrosion degrees was established to study corroded steel wire fracture characteristics by Python and Abaqus.The breaking force degradation empirical formula of steel wire under different corrosion degrees based on the results of the experiment and finite element analysis was put forward.(2)The corrosion fatigue alternate test considering the corrosion fatigue damage of highstrength steel wire in service was carried out to study the fatigue life of steel wire under different corrosion interval times.The effect of corrosion on the fatigue fracture mode of steel wire was analyzed.A damage model based on the damage mechanics of steel wire considering the alternate outcome of corrosion fatigue to calculate the fatigue life of the steel wire was proposed in the dissertation.(3)The corrosion fatigue coupling test of high-strength steel wire was carried out owing to the corrosion fatigue alternate test can not accurately reflect the failure mechanism of highstrength steel wire under the coupling effect of corrosion fatigue.The influence of p H value,temperature,loading frequency,the concentration of corrosion solution and stress ratio on the coupling effect of corrosion fatigue of steel wire were analyzed.A new theory that multi-stage competition assisted corrosion fatigue theory considering the coupling effect of corrosion fatigue was established in the dissertation.The specific content of the theory and the selection of parameters were described via the experimental data.The whole process of steel wire corrosion fatigue fracture was realized in ABAQUS by using the theory.The accuracy of the theory was verified by comparing the calculation results with the experimental results.(4)The investigation was carried out to study the failure mechanism of the parallel steel wire cables to solve the problem of the broken steel wire caused by corrosion fatigue coupling in the parallel wire cables.The concept of bending characteristic length was proposed,and the stress distribution in the anchorage zone was analyzed.The spatial fibre element considering corrosion degree and stress distribution at different positions was presented.The broken wire effect of parallel steel wire cable was calculated by numerical simulation and experiment.(5)A Deep Reference Autoencoder Convolutional Neural Network(DRACNN)was proposed based on the theory of depth learning,which can directly output the damage characteristics of cables and suspenders by vibration signals.The correlation transformation of the vibration signal was directly used to obtain the optimal network structure parameters in network training and extract the information of neuron change through the characteristics of the damage signal in theory.The change information of neurons was used to identify the damage state of the structure by the exponentially weighted moving average control chart.The correctness of the method was verified by numerical simulation and experiment.A set of frame theories for analyzing corrosion fatigue failure and damage state of parallel steel wire cable was presented in the dissertation,providing a reference for engineering designers in the initial design of cable-supported bridges.