Abstract
Steel-truss-arch bridges have been applied in high-speed railway bridges due to their excellent dynamic and static structural performance. Under the action of high-speed trains, the steel connections between hangers and decks suffer from repeated stresses, inducing potential fatigue problems or even fatigue failure. In this study, a multiaxial fatigue evaluation method was first created and established based on critical damage-plane methodology, following which the fatigue evaluation procedure was also created and recommended. The methodology was applied to real-life strain data from a high-speed railway bridge from which an assessment of fatigue damage and predicted fatigue life was estimated. The connection between the shortest hanger and deck on the downstream side was selected as the target due to its relatively high stress. A multiscale finite-element model of this bridge was created according to the design profile and monitoring results of traffic flow, where the finite-element model was calibrated and validated by comparing the calculation results with the monitoring data. Influence analysis was then carried out to investigate two factors—i.e., the total traffic flow and compositions of freight trains—having effects on the fatigue life of the steel connection. The results indicate that the applied multiaxial fatigue method is suitable for online fatigue evaluation of actual bridges. In addition, by using the multiaxial fatigue method, the fatigue-damage accumulation rate can be nearly 60 times that obtained by the uniaxial fatigue method. If freighting is taken into consideration, the fatigue damage will increase rapidly, and for the case 10% of proportion traffic as freighting, the actual fatigue life is estimated to be shorter than the design life.
Highlights
As typical connection members between arch ribs and bridge decks, hangers of arch bridges are required to be robust enough to sustain dead and live loads
Proper accumulation rules must be introduced to account for each instance of fatigue damage and to obtain the fatigue life with the help of the definition of critical damage
The results show that even when the annual growth rate of traffic flow reaches 10%, the fatigue life can be much greater than the design life of the whole bridge
Summary
As typical connection members between arch ribs and bridge decks, hangers of arch bridges are required to be robust enough to sustain dead and live loads. As replacements for traditional cables, rigid steel hangers have been considered specimens with infinite fatigue lives for very small vibration and stress ranges, and the wind- or train-induced fatigue lives for cable-stayed arch bridges have been within the design life requirements [13,14,15]. The critical plane method has been extensively applied in actual projects because of its specific definition of fatigue damage, and the simplification of the critical stress state. According to their different assumptions for failure rules, fatigue damage functions were built by using tensile or shear-related critical planes, where fatigue-failure is dependent on the evolution or accumulation of tensile or shear stress amplitudes. Having obtained the annual fatigue damage of the target part, the influences of two factors, i.e., the total traffic flow and compositions of freight trains, on the fatigue life were emphatically investigated for future bridge maintenance
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