斜拉索模态试验参数研究

A Study on Experimental Modal Analysis of Stay Cables

试验模态分析是斜拉桥索力测试中广泛应用的方法。该方法的关键之一是采取合理的试验方案获取可靠的响应信号以识别出正确的索振动频率。本文通过试验,详细讨论了斜拉索模态测试中若干试验参数,如激振类型、激振位置、传感器位置以及频率分辨率对试验结果的影响;比较环境激励与锤击激励的效果,验证了环境激励的方法也可以准确识别索的频率;最后给出了较为合理的斜拉索模态试验方案,用该方案确定的索力与理论计算结果相差不超过 1. 5%。

Experimental modal analysis and testing is one of the most widely used techniques for the measurement of tension forces in stay cables. For the modal testing of stay cables, adoption of proper experimental methodology for acquiring the reliable signals plays a key role for accurate identification of the cable frequencies. In this paper, a stay cable model experiment was conducted in laboratory to determine the effects of the variables such as type and placement of excitations, arrangement of accelerometers, sampling frequency and frequency resolution etc. Comparing the frequencies identified by the ambient excitation with those by the hammer excitation, it is demonstrated that the ambient excitation is good enough to identify the frequencies of stay cables interested. A feasible experimental procedure was presented for accurate determination of the stay cables frequencies. The results show that the tensions of the stay cable experimentally determined achieve an error of less than 1.5% by comparing those with the theoretical prediction.