人行悬索桥人致振动分析与实测研究

Analysis and test of human induced vibration of pedestrian suspension bridge

人行悬索桥结构自振频率低、整体刚度和阻尼小,人致振动问题需要特别关注。以某景区人行悬索桥为研究对象,采用现场实测与有限元模拟相结合的方式,研究人行悬索桥人致振动响应的规律。考虑不同人群激励方式对人致振动的关键影响因素进行参数分析,包括人群附加质量、激励频率、激励分布和阻尼比,得到了各参数对人致振动的影响。结果表明:人行悬索桥加速度响应与激励人数呈正相关,在相同测试人数下,行走激励的加速度响应随行走频率的增加而增大;人群附加质量对人行悬索桥振动的影响不可忽略,宜根据桥梁的设计承载人数构造振动激励及确定桥面人群附加质量;人行悬索桥频率较低,直接按照步频构造人行激励更为恰当;为获得更不利的人致振动响应,当激励频率与结构某对称竖向振型频率接近时,人群行走激励取为全桥同向分布,当激励频率与结构某反对称竖向振型频率接近时,人群行走激励则按悬索桥的最低阶反对称竖向振型分布。对于一般的人行悬索桥,人致振动分析时阻尼比建议取为0.20%~0.40%。

The natural frequency of pedestrian suspension bridge is low,and the overall stiffness and damping are small,so the problem of human induced vibration requires special attention.The pedestrian suspension bridge is taken as a research object in this study,and the human induced vibration response of pedestrian suspension bridge is investigated by combining field measurement with finite element simulation.Based on the different crowd excitation,the crucial factors including crowd added mass,excitation frequency,excitation distribution and damping ratio are analyzed,and the influence of each parameter on human induced vibration is obtained.The results show that for the pedestrian suspension bridge,the acceleration response of the bridge under crowd excitation is positively correlated with the number of people.Under the same number of participants,the acceleration response under walking excitation increases with the increase of excitation frequency.The influence of crowd added mass on the vibration of pedestrian suspension bridge is not neglectable,so it is suitable to determine the vibration excitation and the crowd added mass according to the designed number of passengers of the bridge.Due to the low frequency of the pedestrian suspension bridge,it is suitable to construct the pedestrian excitation directly according to the step frequency.In order to obtain the most unfavorable dynamic response,when the excitation frequency is close to the natural frequency of the symmetrical vertical mode of the structure,the crowd excitation distribution of the whole bridge is applied in the same direction.When the excitation frequency is close to the natural frequency of the antisymmetric vertical mode of the structure,the crowd excitation is distributed according to the lowest order of antisymmetric vertical mode of the suspension bridge.For the general pedestrian suspension bridge,the damping ratio for human induced vibration analysis is recommended to be 0.20%-0.40%.