Ultra-low frequency vibrations are common on the in-service long-span bridges.Due to the space limitation inside the box girders,conventional tuned mass dampers(TMDs)are not considered the optimal vibration control solution.This paper presents a type of ultra-low frequency tuned liquid mass dampers(TLMDs)that take advantages of buoyancy and fluid-structure interaction.Model tests were carried out to verify the damping effect of TLMDs,and the acceleration amplitudes and damping ratio of the main bridge structure were analyzed before and after the installation of TLMDs.The ultra-low frequency TLMDs have been applied to the Longli River Bridge in Guizhou Province,and the frequency features and damping ratio of the superstructure were examined.The in-door tests and on-site engineering demonstrate that the TLMDs are capable of suppressing the vibrations with frequencies as low as 0.283 Hz and even lower.Fitted with TLMDs,the damping ratio of the main bridge structure rises from 0.038％to 2.2％,while the acceleration amplitude falls from 0.41 m/s2 to 0.01 m/s2.At a mass ratio of 0.31％,the measured damping ratio associated with the first vertical bending mode of the superstructure is increased from 0.20％to 0.82％,3.1 times higher than the damping ratio before the installation of ultra-low frequency TLMDs.The engineering practice proves that ultra-low frequency TLMDs are reliable,with stable parameters,which can be installed lower in heights than the comparable types of dampers,leading to improved damping ratio and better wind resistance of the bridge structure.
关键词
大跨度桥梁/超低频/调谐液体质量阻尼器/阻尼比/室内模型试验/实桥测试
Key words
long-span bridge/ultra-low frequency/tuned liquid mass damper(TLMD)/damping ratio/in-door model test/on-site verification
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