Analysis And Numerical Simulation Of Fatigue Crack In Components Of Long-Span Suspension Bridge With Complex Stress

Under the long-term,repeative application of traffic loads, fatigue damage accumulates and fatigue crack grows in steel bridge components with complex stress, which will not only result in a waste of maintenance repair cost, and may result in sudden fracture of the connection structure. In this paper, for the typical components of long-span suspension bridge, i.e. the cable-girder anchorage and the central buckle, the fatigue damage mechanism under the vehicle load is investigated and fatigue life is evaluated. The work conducted in this paper is summarized as follows:(1) The numerical model for fatigue assessment based on the finite element model, the vehicle load model and the fatigue life evaluation process is established. The finite element model of the whole bridge and the local fine models of the cable-girder anchorage and the central buckling are established by the general finite element software ANSYS. The whole bridge model is checked according to the measured datum, the local fine models and the whole bridge model are linked up by the sub-model technology. The comprehensive probabilistic vehicle load, which contains vehicle type, lane distribution, axle load and wheelbase information is established using data from the toll station. Combined with the finite analysis and the vehicle load probablitity model, the probabilistic finite element fatigue life evalution process is given based on S-N curve.(2) The reason for fatigue cracking of cable-girder anchorage is analysed and the fatigue life of related details is evaluated. Through the statistical analysis of the cracking of the related details of the cable-girder anchorage, i.e. the stiffening rib and the bearing plate connection, the inlined plate and the ear plate connection, the distribution, characteristics and propagation law of cracks are discussed. Through the finite element analysis, the stress characteristics of some details are studied, the cracking reason of the stiffening rib and bearing plate connection, the inclined plate and ear plate connection is discussed. Thereafter the fatigue life of stress concentration region of cable-girder anchorage is predicted. Finally, the optimization structure of the cable-girder anchorage is presented.(3) The stress characteristic of the central buckle is analysised and the fatigue life of related details is evaluated. Through the finite element analysis, the stress characteristic of some details is studied, the reasons for stress concentration of the related details are discussed. Thereafter the fatigue life of stress concentration region is predicted. Finally, the optimization structure of the cable-girder anchorage is presented.