多人随机行走激励下人行桥振动分析

Vibration response analysis of long-span footbridge to random walking loads generated by crowds

大跨人行桥具有轻质、轻柔、阻尼小及低频等特点,基频较小时对人行荷载激励较敏感,但目前对其在多人随机行走下的随机振动问题研究较少。本文基于标准步行荷载,使用人行桥多点加载模型,推导了多人随机行走下大跨人行桥振动响应时程的精细时域计算方法,并以此验证本文提出的计算人行桥随机振动的更简便的谱分析方法;通过构造桥上落足点的荷载时程,变换得到荷载时程功率谱,再利用荷载功率谱并借鉴林家浩教授提出的虚拟荷载法推导出反映行人舒适度的均方根加速度频域计算方法。

Excessive vibrations have become a major serviceability consideration in long-span footbridge with notable characteristics of light weight,high flexibility,small damping and low natural frequency.Based on the vertical walking load model and the multi-point loading model,the paper develops the fine time domain method to calculate footbridge vibration response excited by pedestrain,and further the more convenient spectral analysis method.In the spectral analysis,firstly,the vertical force time history in the standing point is formulated;then the load power spectrum is obtained by FFT technique;finally,the root-mean-square acceleration,which reflects walking comfort,is analytically deduced by the pseudo excitation method（PEM）brought forward by Professor Lin Jiahao.According to comparison of the two methods above,the paper validates the effectiveness and efficiency of the spectral analysis method.