Experimental and numerical aerodynamic optimization of a post-tensioned concrete railway bridge in tandem arrangement with a truss road bridge

Abstract eng:
This paper deals with the aerodynamic design of the Rio Ozama railway bridge in St. Domingo on the Metro line 2, which is in tandem arrangement with an existing truss road bridge. The aerodynamic performances of the deck were studied using wind tunnel tests on 1:20 scale sectional models, and 2D steady RANS CFD simulations were used to preliminary investigate the effects of different tailoring of the deck shape aimed at optimizing its aerodynamic behavior. The initial shape of the deck, which was a classical bluff section, showed poor aerodynamic performances, like large drag coefficient, negative derivative of the lift coefficient, and negative aerodynamic damping inside the design wind speed range. Due to the advanced stage of the design and to structural limitations, it was not possible to switch the shape of the deck to a classical streamlined closed box, and only minor modifications were allowed. The shape tailoring was studied for the stand-alone configuration by means of CFD RANS simulations and experimentally verified in tandem arrangement through wind tunnel tests also at low reduced velocities. The optimization procedure led to three main changes that allowed to achieve an optimal aerodynamic behavior: embedded rails, rounded trailing edges, and enhanced barrier porosity. The work presented shows how CFD simulations can be inserted into a typical wind tunnel tailoring of deck sections. They can be a powerful tool to understand what changes can be more effective, since it is possible to decompose the contribution of each part of the deck section to the overall aerodynamic behavior, and to understand which tailoring can be more effective.

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