Ambient Vibration Survey and Vibration Serviceability Evaluation on Footbridges

摘要

Altogether 37 footbridges were randomly chosen in Beijing metropolitan and ambient vibration surveys were carried out. The vertical fundamental frequencies are obtained by peak-picking technique based on frequency domain decomposition, the damping ratios are calculated by half-power bandwidth method. The fundamental frequencies are mostly in the range of 2-7 Hz, the damping ratios are mostly in the range of 0.2-0.8%. Combining Chinese industrial standard of Technical Specifications of Urban Pedestrian Overcrossing and Underpass and British bridge design code of BS 5400, the vibration serviceability is evaluated. The results show that the footbridges with fundamental frequencies lower than 3 Hz cannot satisfy vibration serviceability requirements, the footbridges with fundamental frequencies at 3-5 Hz can generally meet the demand of peak acceleration limits given in BS 5400, but a certain footbridge responds excessively, the footbridges with fundamental frequencies higher than 5 Hz can easily meet vibration serviceability requirements. The results of dynamic parameters and vibration serviceability evaluation of footbridges can give some help for footbridge design practice.