Third Bosporus Bridge Aerodynamics: Sectional and Full-Aeroelastic Model Testing
The assessment of the aerodynamic performances of the Third Bosporus Bridge (BB3) has been realized through tests in two different Wind Tunnels, CSTB and Politecnico di Milano (POLIMI) and with different scale factors. The design process of a super long span bridge is strongly influenced by the wind actions on the bridge itself and the definitions of wind loads and wind induced dynamics cannot be done without relevant experimental campaigns. The definition of the local wind characteristics is the preliminary experimental test to be done, and the final verification of the bridge response to turbulent wind is the last stage of the wind design. For the Third Bosporus Bridge all these activities have been undertaken in close collaboration by the two cited laboratories. The collaboration granted a cross check of the results and of the test methodologies and hence assured a good reliability of the collected experimental data-base. In particular, at CSTB two sectional models with different scale factors 1:100 and 1:25 have been tested to assess the bridge stability, the response of the deck to vortex induced vibrations and to define the wind profile on the different lanes, and consequently the wind lateral loads on passing vehicles. Moreover, at CSTB a model of a tower has been tested in a very large scale and high Reynolds number to understand the wind interaction of the stand-alone tower during the erection stages. At POLIMI the overall wind response have been tested using a full bridge 1:180 aeroelastic model to define the bridge response to turbulent wind and to check the bridge stability limit also during the erections stages. Finally a large 1:50 scale multi modal aeroelastic model simulating the torsional and vertical bending deck behavior was also tested in order to check in a larger scale possible vortex shedding induced vibrations as well as for a cross check with CSTB of possible Reynolds Number effects on the porous wind screens. The results of the experimental activities gave to the design team all the information needed to consider the wind response and highlighted the very good behavior of the bridge under wind actions from all the point of view: stability, vortex induced vibrations, wind loads and effects on the passing vehicles.
KeywordsWind Tunnel Wind Load Turbulent Wind Vortex Induce Vibration Reynolds Number Effect
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