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本文阐明了利用脉冲瞬态激振对一个大型混凝土坝的模态参数进行的识别。输入脉冲是由自制小火箭形成的。脉冲宽度约为5—6毫秒,最大荷重为3868公斤,在50赫兹以内可以等谱输入。 在信号处理中,为了解决采样率与脉冲宽度的矛盾,一方面在HP3582机上进行细化分析,另一方面利用土木建筑的超低频性质,将输入脉冲及输出响应通过很低频率的低通滤波器,这时传递函数不变,而输入信号在时域上延长了,有利于加长采样时间,提高分辨率。 在识别中采用了实模态识别法,识别出前13个模态参数,并与稳态激振、环境振动及有限元计算进行了比较,结果是比较符合的。 本文还就瞬态激振对大型水工建筑物原型试验的应用进行了讨论。
This paper illustrates the use of pulsed transient excitation to identify the modal parameters of a large concrete dam. The input pulse is formed by a homemade rocket. The pulse width is about 5-6 milliseconds, and the maximum load is 3868 kilograms. The input can be equalized within 50 Hz. In the signal processing, in order to solve the contradiction between the sampling rate and the pulse width, on the one hand, a detailed analysis is performed on the HP3582 machine. On the other hand, using the ultra-low frequency nature of civil engineering, the input pulse and output response are passed through a very low-frequency low-pass filter. At this time, the transfer function is unchanged, and the input signal is extended in the time domain, which is conducive to longer sampling time and improved resolution. The real modal identification method was used in the identification and the first 13 modal parameters were identified. The comparison with the steady-state excitation, environmental vibration, and finite element calculations was quite consistent. This article also discusses the application of transient excitation for prototype testing of large-scale hydraulic buildings.