同时，通过统计分析给出第二振型、第三振型周期与基本周期比值的经验公式。
In addition, the empirical formulas for estimating the ratios of 2nd and 3th mode periods to the fundamental period are put forward through statistical analysis.
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。
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.
第二章介绍了移动荷载识别的基本原理和相关知识，包括振型的正交性，模态叠加原理等。
The second chapter introduces the basic principle and the correlation knowledge of moving load identification, including mode shape orthogonality, mode superposition principle and so on.
第二部分提出振型应变差的概念。
In the second part, the difference of modal strain is introduced.
首先在第二种约束方式下，利用有限元模态分析方法对几种不同板厚的机架进行了动、静态分析，得到了机架变形、应力及各阶振型与频率。
First, using second constrain, the static state and dynamic analysis applied to the frame of a few thickness plates with FEM modal analysis, distortion, stress, vibration and frequency were gained.
首先在第二种约束方式下，利用有限元模态分析方法对几种不同板厚的机架进行了动、静态分析，得到了机架变形、应力及各阶振型与频率。
First, using second constrain, the static state and dynamic analysis applied to the frame of a few thickness plates with FEM modal analysis, distortion, stress, vibration and frequency were gained.
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