钢连桥人致振动及TMD减振效应实测与分析
Analysis and In-situ Test of Human-Induced Vibration for the Steel Footbridge with and Without TMD Devices

以某室外大跨轻柔钢结构人行桥为案例，介绍了该结构的设计概况及调谐质量阻尼器(tuned mass damper，简称TMD)减振设计，分别在结构施工完成后以及TMD装置安装后对其进行了实地动力测试，测得了该结构减振前后的模态特性以及在多种人行荷载工况下的振动响应，采用加速度峰值和均方根值为评价指标，分析了钢连桥人致振动情况及特性。结果表明：一端设计为滑动连接的钢连桥人致振动主要由第1阶竖向振型控制，扭动及水平振动响应相对较小；安装经优化设计的TMD装置后，整体连桥的频率特性没有明显变化，分布式TMD对多种频率激励工况均有良好的调谐减振作用，减振率达到35%~70%；共振激励下测得的原结构阻尼比较小，安装TMD后结构的阻尼比提高4倍，并且呈现出在自由振动衰减的前期较大，随着振动幅度变弱阻尼比降低；测试中发现TMD装置的减振效率对其阻尼比的变化不敏感。
A steel structure footbridge characterized by its flexibility and long span is taken as a case. The designs of the structure and tuned mass damper (TMD) systems are introduced. In situ measurements are conducted after construction and after the installation of TMD devices. Then, the modal properties and vibration responses under various pedestrian load conditions with or without TMD devices are obtained. The human-induced vibration properties are analyzed based on the acceleration peak and acceleration root mean square (RMS) value. The results indicate the following: The vibration of the steel footbridge is dominated by the first vertical mode when one end of the bridge is designed as a sliding connection, and the torsional and horizontal vibrations are relatively small. There is no obvious difference in the vibration properties of a footbridge after TMD devices are installed. The distributed TMD produces good vibration tuned effects for the various excitation conditions with reduction ratios of 35%-70%. Moreover, the damping ratio increases over four times the value without TMD, which is very small before installation. The damping is large at the earlier stage of the free attenuation response and decreases with decreasing vibration amplitude. Lastly, the TMD′s efficiency in vibration reduction is insensitive to variation of the TMD damping ratio.