| 摘要: |
| 自振频率是评估结构动态变形和受力性能的关键因素,现有冷却塔结构自振频率主要基于有限元分析手段,缺乏简单有效的冷却塔自振频率估算公式.为解决该问题,以国内某179 m高的大型冷却塔为基准塔,首先通过改变结构典型参数获得基准塔的38个模型并进行动力特性分析,同时提炼出基频频率随结构参数的变化规律；然后采用拉丁超立方抽样法进行结构自振频率参数的敏感性分析,获取了不同阶数下各参数的敏感因子.在此基础上,创新性地拟合提出考虑敏感因子权重值的多参数的基频实用估算公式.最后,选择国内8座典型塔高和塔型的冷却塔进行现场测试,采用不同模态识别方法获得冷却塔前10阶自振频率,进行了实测冷却塔结构参数的拟合优度分析.研究表明:自振频率对冷却塔高度最为敏感,其敏感因子显著大于其它参数的敏感因子；实测塔计算结果验证了基频实用估算公式的有效性,基频拟合优度最大值为0.996,其中各目标塔拟合优度的均值和均方差分别为0.948和0.047.误差分析表明本文提出的自振频率估算公式精度高、稳定性好. |
| 关键词: 冷却塔 自振频率 敏感性分析 现场实测 模态识别 估算公式 |
| DOI：10.11918/j.issn.0367-6234.201805008 |
| 分类号:TU279.7+41 |
| 文献标识码:A |
| 基金项目:国家自然科学基金(1,4);江苏省优秀青年基金(BK20160083) |
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| Estimation method and goodness of fit analysison natural frequencies of large cooling towers |
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XU Lu,KE Shitang
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(Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China)
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| Abstract: |
| The natural frequency is the key factor that determines the dynamic deformation and stress of structure.The natural frequencies of the existing cooling towers are mainly obtained by finite element analysis, and there is no simple and effective formula for estimating the natural frequencies of the cooling towers.To resolve this problem,a large cooling tower was takenas the reference tower. Firstly, 38 models were obtained by changing the typical parameters of the reference tower, and the dynamic characteristics were analyzed.The law of fundamental frequency changing with the structure parameters was also extracted.Then, the sensitivity of the structural natural frequency parameters was analyzed by Latin hypercube sampling method, and the sensitive factors of various structural parameters under different orders were obtained.On this basis, the practical estimation formula of multi-parameter fundamental frequency considering sensitivity factor weight was innovatively fitted. Finally, eight cooling towersof typical height and typein China were selected for the field measurements, and the first 10-order self-oscillation frequencies of cooling tower were obtained by different mode identification methods.Further, the goodness of fit was analyzed using eight seat structure parameters of cooling tower. The results show thatthe natural frequencies are most sensitive to the height of cooling towers, and the sensitive factors are significantly higher than those of other parameters.By using 8 measured towers, the formula for estimating fundamental frequency isverified. The maximum value of self-vibration frequency fitting is 0.996, in which the mean value and mean variance of each target tower are 0.948 and 0.047, respectively. The estimation formula ofthe natural frequencies is of high accuracy and stability. |
| Key words: cooling tower natural vibration frequency sensitivity analysis field measurement modal identification estimation formula |
