3

The result was that the vortex-excited vibration would be induced in both smooth and turbulent flows. Aerodynamic countermeasure of fairing, double flap, and skirt (as shown in Figure 13.60) was examined to suppress the vortex-excited vibration. The vortex-excited vibration could not be suppressed (as shown in Figure 13.61). This means that it is very difficult to suppress the aeroelastic vibration of a steel box girder bridge by aerodynamic countermeasure through changing the structure configuration. Therefore, in this example, a tuned mass damper (TMD) was used for suppression of vortex-excited vibration.

Figure 13.62 shows the comparison of aerodynamic responses of first mode in both the wind tunnel tests and the field measurement before being opened to the public. In the figure, solid lines show the results of wind tunnel tests for two structural damping decrements of d = 0.028 and 0.044. The other points are the field measurement results measured in the wind for bridge axis right angle within ±20°and the turbulent intensity of 4 to 10%. These results prove that the accuracy of the wind tunnel test is high. The maximum amplitude was measured around a wind velocity of 16 m/s and the result was

- Offshore-^-Shallow

FIGURE 13.59 Outline of the Trans-Tokyo Bay Highway [45].

- Offshore-^-Shallow

FIGURE 13.59 Outline of the Trans-Tokyo Bay Highway [45].

L/2 Center of span

Shape

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