Crosswind aerodynamic characteristics of a stationary interior railway carriage through a long-span truss-girder bridge

Abstract This paper investigates the aerodynamics of a stationary model of an interior railway carriage inside a long-span truss-girder bridge in a wind tunnel. Effects of principle parameters of the truss bridge-girder configuration on the aerodynamics were examined, including bridge wind angle of attack (α), truss bridge-girder solidity ratio (Φ, projected area to envelope area ratio), and aspect ratio (B/D, truss bridge-girder width to height ratio). By varying α, the tested pressure distribution of the carriage model was analyzed in terms of the underlying flow physics of the carriage-bridge interaction. Consequently, the schematic flow patterns were inferred and subsequently utilized to expound the variations in the mean and fluctuating aerodynamic force coefficients. The results indicate that qualitatively the aerodynamic interaction of the truss bridge-girder on the carriage model is characterized by the shielding effect caused by upstream truss members, the suppression of underbody vortex-shedding due to the girder lower deck, and the quasi-Reynolds number effect on the upstream carriage shoulder. Compared to the results of the carriage model without the truss bridge-girder, the shielding effect reduces the mean drag force, whereas the suppression of underbody vortex shedding decreases the mean rolling moment and all the fluctuating forces. The quasi-Reynolds number effect surfaces as α varies given that the inflow Reynolds number is held constant, thus altering the aerodynamic forces abruptly. For the variation of the other two truss bridge-girder configuration parameters (Φ and B/D), qualitatively similar carriage-bridge interaction on the carriage aerodynamics was observed, although with some quantitative differences. The imperfect spanwise correlation of sectional aerodynamics was also observed as mostly owing to the shielding effect formed by the diagonal truss members. In addition, the influence of carriage-bridge interaction on the bridge aerodynamics was also examined and briefly discussed.