应县木塔环境振动试验

对于复杂的塔状古建筑物,建立一个合适的简化的数学模型是不易实现的。与强迫振动试验相比,环境振动试验比较简单、方便,所确定出的小振幅水平下的木塔结构动力特性具有足够的精度。本文首先结合应县木塔结构环境振动测试实例对环境振动测试方法作了简要介绍,并采用随机信号数据频域分析方法对测试数据进行了分析,确定木塔结构的自振频率。同时,依据不同测点在固有频率处响应的比及零迟时互相关函数确定木塔结构的振型。最后,本文依据自功率谱和互功率谱采用半功率点法计算各振型的阻尼比。本文分析结果表明,在两水平方向上木塔的振动特性存在些微差异,第一振型阻尼比较第二振型阻尼比大。

Ambient vibration test of a wood tower in Ying County

It's not easy to build a mathematic model for the complex structures,such as ancient towers.Compared with forced vibration tests,the ambient vibration test is more convenient and it has enough accuracy for the small amplitude response characteristics.In this paper,the method of ambient vibration test is applied for measuring a wood tower in Ying County,Shanxi,China.In the frequency domain,the method of random signal data analysis is performed to obtain the natural frequencies.Then the mode shapes of the wood tower are determined based on the mode amplitudes at each observation point and zero delayed cross-correlation function.Finally,the damping ratio of each mode is calculated by using the half-power point method on the basis of auto power spectrum and cross power spectrum.The results show that the vibration characteristics of the tower in two horizontal directions are slightly distinct,and the damping ratio of the first mode is greater than that of the second mode.