Wind tunnel test study of aerodynamic characteristics of trains on double truss bridges

In order to study the aerodynamic characteristics of trains on the upper and lower levels of a doublelayer truss bridge, force and pressure measurements of trains on the main girder section of double deck trusses were carried out by segmental model wind tunnel tests. In this paper, a large span public-rail suspension bridge and a CRH2 train were used as the background to study the aerodynamic coefficient, mean pressure coefficient and fluctuating pressure coefficient of trains on the upper and lower levels of the main section of the double-layer truss bridge under headwinds and crosswinds, and the effect of the attack angle on the aerodynamic coefficients of the trains on the upper and lower were analyzed. The research results show that: (1) the drag coefficient of the upper train is significantly smaller than that of the lower train, when the train is located windward side, the drag coefficient of the lower train can reach 1.6 timesthat of the upper-level train., and the magnitude of their moment coefficients basically the same, but the lift coefficient of the upper train is larger than of the lower train; the drag coefficients of the upper and lower trains decrease gradually with the increase of the attack angle and the difference between them also decreases. (2) The pressure difference between the windward and leeward sides of the upper train id significantly smaller than that of the lower train, making the overall drag of the upper train is smaller than that of the lower train, and the pressure difference between the top and bottom of the upper train is greater than that of the lower train, making the overall lift of the upper train greater than that of the lower train; the mean pressure on the windward side of the upper train decreases with the increase of the attack angle, while there is no significant change in the lower train. (3) The fluctuating pressure coefficient at the top and bottom of the circular transition section of the upper train is smaller than that of the lower train, and with the increase of the wind attack angle, the fluctuating pressure coefficient of the lower train decreases, while there is no significant change in the upper train, the attack angle has less effect on the fluctuating of the pressure coefficient in the upper train. The results of this study can provide reference and guidance for train line arrangement on double deck truss bridge. © 2023, Central South University Press. All rights reserved.