Fatigue Calculation And Analysis Of Suspension Rods Of Self-anchored Suspension Bridges Based On Stress Intensity Factor

Suspension bridge is a type of bridge with suspension cable as the main load-bearing structure,in which the suspender is the key part connecting the main cable and the stiffening beam.In the process of using,the suspender is easy to be affected by the surrounding harsh environment and temperature,which leads to corrosion and deterioration and crack.The suspender bears vehicle load and wind load for a long time,and the suspender is prone to fatigue under the action of alternating load..With the increase of the number of suspension bridges,the fatigue problem of suspender becomes more and more serious.Taking Nanjing Jiajiang bridge as the engineering background,the fatigue problem of suspender of self-anchored suspension bridge is studied and analyzed in this paper.This paper introduces the method to determine the reasonable finished state of the space cable self-anchored suspension bridge,and then takes the jiajiang bridge as the background,determines the reasonable finished state of the bridge,and verifies the rationality of its force.Secondly,the fatigue stress spectrum of the suspender is calculated by using relevant auxiliary software in combination with relevant standard and traffic data.Then,the spline virtual boundary element method based on Kelvin basic solution and the displacement extrapolation method were extended from plane to 3d to calculate the stress intensity factor of the suspender.The nominal stress method for calculating the fatigue life of suspender without initial crack and the fracture mechanics method for calculating the fatigue life of suspender with initial crack are described.Finally,the XFEM function of ABAQUS software is used to simulate and analyze the crack growth of suspender with initial crack.The results show that the calculated value and the designed value of the suspender force are close to each other and the structural force is reasonable.The calculated stress intensity factor has a small error with the result calculated by ABAQUS,a large-scale general finite element software,which verifies the applicability and accuracy of the spline virtual boundary element method combined with displacement extrapolation method based on Kelvin basic solution.Through literature review,it is found that the fatigue life of the suspender without initial crack is infinite in the designed service life.When introducing the method of calculating fatigue life by fracture mechanics,due to the limitation of experimental conditions,the calculation accuracy of stress intensity factor is found to have an influence on the calculation accuracy based on fracture mechanics fatigue life by observing the formula form.The stress concentration phenomenon appears in the crack of boom,when the crack expands,under the influence of crack,the stress of boom will produce eccentricity.