Discussion on validity of structural response by Nakamura’s technique
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摘要: 日本学者中村(Nakamura)1989年提出了一种基于同一地表测点地脉动水平分量与竖向分量傅里叶振幅谱比值来估计场地特征的方法， 即所谓的中村方法. 该方法被广泛应用于场地特征的估计， 并已取得大量的成果. 目前， 这一方法也被国内外的研究人员用来进行结构响应特征的研究. 但中村方法的合理性， 国内外尚存在较大争议. 通过对北京城区的一栋钢筋混凝土框架结构建筑的脉动观测， 采用中村方法对获取的速度记录进行了计算分析. 结果表明， 该方法能有效地得到结构的自振频率， 但是不能给出结构对振动的真实放大倍数， 因此， 在使用此方法分析结构响应方面时应谨慎， 建议采用多种方法进行比较分析.
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关键词:
- 中村(Nakamura)方法 /
- H/V谱比 /
- 结构响应 /
- 有效性
Abstract: A method called Nakamura’s technique, which uses a horizontal-to-vertical Fourier spectrum ratio (H/V ratio) of microtremor to estimate the dynamic characteristics of a site, was introduced by a Japanese scholar Nakamura in 1989. This technique is widely used, and fruitful achievements in scientific research are presented by this technique. Nowadays, this technique is also used to estimate the structural response characteristics by home and abroad researchers. However, the validity of Nakamura’s technique is still in dispute. The ambient seismic noise measurement was conducted inside a reinforced concrete (RC) building in urban area of Beijing. The calculative analysis on velocity data by Nakamura’s technique is done. The analyses indicate that the natural frequency can be obtained validly by the Nakamura’s technique, but the magnification is not accurate. We must use this technique to estimate structural response characteristics carefully, and we suggest other methods should be used simultaneously to compare.-
Keywords:
- Nakamura’s technique /
- H/V ratio /
- structural response /
- validity
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图 2 仪器(三角形)布设位置和大楼EW向结构截面图
Figure 2. Structural section (EW) of the reinforced concrete building and the location of 16 stations (denoted by triangles)
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图 3 五楼西端三分量速度记录的振幅谱(a)和EW/V、 NS/V和H/V振幅谱比值(b)
Figure 3. The amplitude spectra of the three components on the fifth floor of the western end (a) and the spectral ratios of EW/V， NS/V， and H/V (b)
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图 4 大楼西端各层记录信号的EW/V、 NS/V、 H/V振幅谱比值(第二层数据不能用)
Figure 4. The spectral ratios of EW/V， NS/V， H/V on each floor of the western end (The date for the second floor are not used)
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图 5 大楼东端各层记录信号的EW/V、 NS/V、 H/V振幅谱比值
Figure 5. The spectral ratios of EW/V， NS/V， H/V on each floor of the eastern end
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图 6 大楼西端各层记录信号的水平向和竖向传递函数(第二层数据不能用)
Figure 6. The transfer function for horizontal and vertical components of the records on each floor of the western end (The date for the second floor are not used)
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