Abstract：Abstract：Research purposes： The debris flow impacts give rise to additional deformations of the ballastless track on bridge, resulting in threats to the operation of high-speed trains. One key to study the problem is to determine the debris flow load model and its influences. A simplification model of the debris flow load is presented in this paper, which considers the slurry pressure, boulder impact and the effect of dragon-head and dragon-tail. A multi-span simple beam bridge on Chengdu-Lanzhou high- speed railway is taken as the study case, and the three-dimensional finite element model of the ballastless track-bridge is built to investigate dynamic responses in terms of lateral displacements at piers' top, lateral displacements at girders' mid-span and lateral relative displacements of rail supports at the end of adjacent spans. At last, parametric studies are carried out to study the influence rules. Research conclusions： (1) The occurrence moment of the peak dynamic response is slightly later than the time of boulder impacts, and the dynamic responses are sensitive to the magnitude and height of the debris flow load. (2) Dragon-head and dragon-tail effects give rise to significant differences on lateral displacements at piers′ top and lateral displacements at girders′ mid-span, while marked variations only appear in the dragon-tail part for lateral relative displacements of rail supports at the end of adjacent spans. (3) The lateral displacements at piers′ top and the lateral displacements at girders′ mid-span are observed to be slightly increased by increasing the duration of the single boulder load; however, significant increases are found in the lateral relative displacements of rail supports at the end of adjacent spans. (4) The research results can provide good reference for subsequent study of running safety of high speed trains on bridges subjected to debris flow impacts.
2018, Vol. 35 
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