Influence of Steel Truss Girder Section Type on Aerodynamic Characteristics of Trains on Rail-cum-Road Bridge
Different steel truss girder section types may change the aerodynamic forces of trains on the bridge,which in turn affect the safety and comfort of the train operation on the bridge.To this end,based on a kilometer class rail-cum-road suspension bridge,this paper conducted force and pressure tests on trains running on the bridge with three common steel truss girder section types through wind tunnel tests.The results show that when a single train is located upstream of the three types of steel truss girder sections,no significant difference exists in the drag and lift coefficients of the train,while when a single train is located downstream,there is great difference in the drag and lift coefficients of the train.In the double-train state,due to the blocking effect of the train on the windward side,the flow field of the train under dif-ferent steel truss girder cross-section types is changed,causing minor impact of steel truss girder section type on the train on the leeward side.Whatever the train is located upstream or downstream,the variation trend of drag coefficient and lift coefficient of the train under the three steel truss section types is the same with the change of wind angle of attack.When the train is in the upstream,different levels of flow separation appear on the top of the train on the three steel truss girder sections and the bottom arc transition section,resulting in different mean wind pressure coefficients of the train.When the train is located downstream,the variation trend of the mean wind pressure coefficients of the train on the three steel truss girder section types is the same,indicating that the steel truss girder section type has little impact on the mean wind pressure coefficients of the downstream train.When the train is located upstream or downstream,a significant difference may exist in the fluctuating wind pressure coefficients,with the coefficients more significantly affected by the steel truss girder layout form than by the height of the girder.The results of the study can provide reference and basis for the selec-tion of section types for large span steel truss bridges.
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