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Title:: Mode Identification of High-rise Reinforced Concrete Structures Based on Ambient Vibration Test

Author(s):: WEN Rui-zhi¹; 2; HU Jin-jun¹; ZHOU Zheng-hua¹; (1. Institute of Engineering Mechanics, CEA, Harbin 150080, Heilongjiang, China)(2. Beijing University of Technology, Beijing 100022, China)

Keywords:: high-rise building; ambient vibration test; natural frequency; mode shape; damping ratio

摘要:: 根据高层钢筋混凝土结构环境振动测试数据,采用随机信号的频域分析方法,确定了高层结构的自振频率; 基于不同测点在固有频率处的响应比及零迟时互相关函数确定了结构的振型; 运用自功率谱和互功率谱,采用半功率点法计算了各阶振型的阻尼比。结果表明,环境振动测试能够较好地识别高层结构的1～3阶振型。对实测自振周期与《建筑结构荷载规范》的公式和数值模拟结果进行比较,发现:结构的层数小于20层时,实测值与《规范》规定的值最接近; 结构超过20层时,实测值小于《规范》规定的值和数值模拟的结果。

Abstract:: Based on the ambient vibration tests of high-rise reinforced concrete structures, the test data are performed in frequency domain and the natural frequencies of the buildings are determined; then the mode shapes of the high-rise buildings are determined based on the mode amplitudes by cross-correlation function between two different observation points; finally,the damping ratios of each mode are calculated using half-power method based on auto-power spectrum and cross-power spectrum. The results indicate that the 1st-3rd mode shapes can be obtained from the ambient vibration tests. Also, by comparisons of natural periods derived from ambient vibration test and some other methods, it is shown that the natural periods obtained from ambient vibration is similar to those derived from empirical relationship. When the building is under twenty stories, the period is similar to the results from other methods; and when building is higher than twenty stories, the period is smaller than those from the other methods.