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Three viaducts constructed with steel box-girders in series, Ishimaru, Meinohama-Ishimaru and Muromigawa, on Fukuoka Expressway No.1 were opened to traffic in October 2001. They are characterized by: (1) the viaducts for the east and west bound lanes have been built closely in parallel (excluding the Muromigawa viaduct), (2) the weight of the superstructure has been reduced by adopting a steel deck, (3) the maximum span between bridge piers is about 100 meters and (4) sound insulation walls 4.5 m in height have been installed. For the above design features, the wind-resistance stability of the viaduct models was examined using a wind tunnel. The test results revealed that vortex-induced vibration and wake galloping were likely to occur, so vibration controls were studied. The field tests were conducted as a part of the study on wind-resistant stability. By exciting the viaducts near completion with a pair of gigantic shakers, natural frequencies, modes of vibrations and structural damping were measured. Based on the field test results, five units of tuned mass dampers have been installed at the Meinohama-Ishimaru viaduct for vortex-induced vibration control. |
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