双向行走激励条件下人行桥的随机振动问题研究  

RANDOM VIBRATION OF FOOTBRIDGE GENERATED BY CROWDS’ TWO-WAY WALKING

作　　者：李泉[1] 樊健生[1] 聂建国[1] 

机构地区：[1]清华大学土木工程系土木工程安全与耐久教育部重点实验室,北京100084

出　　处：《工程力学》2010年第7期74-81,共8页Engineering Mechanics

基　　金：北京市自然科学基金项目(8052013);长江学者和创新团队发展计划项目(IRT00736)

摘　　要：多人双向行走条件下人行桥的随机振动对城市大跨梁式人行桥的竖向振动估计及其控制有重要意义。该文基于桥上人群双向行走的交通流特征,利用随机振动的基本理论和虚拟激励法,发展了适于多种边界条件以及跨度布置的人行桥桥上各点加速度功率谱密度函数的计算方法,该方法适于描述人群按各种不同方式上桥行走的交通状况。计算结果表明:该文提出的加速度功率谱密度函数计算方法和时域方法吻合良好,满足工程计算的效率和精度要求;即使满足现行设计规范(承载力、挠度、基频f>3Hz)的人行桥,也会因人群荷载的高阶傅里叶级数分量引发的人桥共振而产生振动过大的问题;相比单向行走,人群的双向行走将对不同共振模态的人行桥产生不同的激励效应,共振模态为对称时为相互叠加,共振模态为反对称时为相互削弱。This paper investigates the crowd-footbridge random vibration in the consideration of a two-way walking of crowd. For this purpose, a random vibration model is developed. In this model, the gamma distribution, widely used in traffic flow theory to describe the headway distribution, is adopted to generate the crowd flow. FFT technique is employed to obtain load power spectral density （PSD） in the exciting points and then the acceleration PSD of any position is calculated by a pseudo excitation method. The results show that the acceleration PSD predicted by the random vibration model agrees with that evaluated by a time domain method. Also, when the footbridge frequency falls within the frequency bandwidth of a crowd excitation, the excessive vibration caused by crowd-footbridge resonance, has a tendency to exceed the vibration comfort requirement of pedestrians, although the footbridge accords with the current footbridge design code in China. Moreover, the footbridge vibration corresponding to the two-way walking of crowd differentiates from that of a one-way walking. Namely, the two one-way walking effects superpose if the footbridge vibration mode of resonance is symmetrical, or otherwise counteract if it is asymmetrical.

关 键 词：人行桥 人群 振动 随机振动 双向行走 

分 类 号：U441.3[建筑科学—桥梁与隧道工程]