| During the design reference period of normal service of bridge,the steel wire for cables is corroded and damaged due to long-term corrosion by environmental factors such as high temperature,high humidity and high salt,and corrosion pit defects appear on the surface of steel wire,which significantly weakens its mechanical properties such as fatigue.During the design reference period of normal service of bridge,the steel wire for cable is corroded and damaged due to long-term corrosion by environmental factors such as high temperature,high humidity and high salt,and corrosion pit defects appear on the surface of steel wire,which significantly weakens its mechanical properties such as fatigue.In addition,the continuous action of vehicle load and wind load along with the dynamic load makes the cable steel wire become the lowest life and the most easily damaged part in the normal operation of the bridge.When the steel wire with corrosion defects occurs fatigue failure,it often presents a brittle failure without warning,which seriously threatens the safety of human life and property.Therefore,it is of great engineering significance to study the fatigue strength and other mechanical properties of the cable steel wire with corrosion pit defects,and then accurately evaluate and predict the safety state and service performance of the cable during the service period,which is of great engineering significance for the safe operation and scientific maintenance management of the bridge using the suspension cable components.In this paper,the fatigue performance and residual fatigue life of cable stayed cables under random load are studied by using finite element analysis method based on the bridge actual test data and pre corrosion fatigue test results.The main research work and conclusions are as follows(1)According to the results of acetic acid salt spray pre-corrosion test of high-strength galvanized steel wire for cable body structure,the corrosion grade of steel wire is divided according to the mass loss rate.The simplified pit model was determined by three parameters of length,width and depth,and randomly distributed on the surface of steel wire specimen model.Through the finite element calculation,the stress distribution of the specimens with corrosion pits in each corrosion grade is studied and the position of the maximum equivalent stress value is determined.(2)The fatigue test results of pre corroded steel wire specimens are analyzed,and the constant amplitude sine wave load simulation is carried out by using the model with corrosion pit defect.According to the fatigue failure mechanism and fracture morphology characteristics,it is determined that the best coincidence position of steel wire fatigue life in the model life nephogram is between 1/3~1/2 of the diameter length from the fatigue crack area along the diameter direction.At this time,the fatigue performance calculation of the model is in good agreement with the fatigue test results,which has enough accuracy for fatigue life prediction.(3)According to the statistical characteristics of traffic vehicles in a bridge example,the vehicle load is simulated,and according to the conclusion of wind load model load spectrum based on measured wind parameters superimposed by stress time history,a fatigue load spectrum with sufficient accuracy is proposed.The residual fatigue life prediction value under random load is obtained by loading into the corrosion pit specimen model.(4)Different fatigue cumulative damage theories are analyzed and compared,and their usability and applicability are discussed.Based on the fatigue test data of pre corroded suspender wire,the stress life curve(S-N curve)under different corrosion grades was fitted.On this basis,the fatigue life of corroded steel wire under random load spectrum is calculated.Compared with the corrosion pit model numerical simulation test method,the deviation degree is larger when the corrosion degree is small,and the residual fatigue life prediction results are similar with the corrosion degree deepening. |
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