环境激励下高层建筑结构模态测试与有限元建模分析

Ambient vibration dynamic test and finite element analysis for high-rise buildings

对高层建筑在环境激励下现场实测以及随机振动分析,所获得的频率和振型等模态信息对于高层建筑结构的动力性能评估和抗震设计有着重要的意义。介绍广西来宾的高层建筑动力测试项目,对8栋高层建筑结构进行系统地随机振动信号测试,通过互相关函数分析和傅里叶变换从而得到结构的互功率谱,利用设置参考点进行分步试验获得结构的工作模态,从而获得结构振动的自振频率等重要参数。在PKPM软件和Sap2000软件中建立高层建筑有限元模型从而来获得结构振动的计算频率和振型。为了研究填充墙的刚度和质量对高层结构动力特性的影响,在Sap2000软件中特别建立三种有限元模型。通过研究发现测试所得到的结构的基频为常用设计软件PKPM计算基频值的2倍以上,另外合理地选用壳单元模拟剪力墙刚度并考虑填充墙质量作用于梁上能较准确地估计结构实测模态值。最后将本次对8栋高层结构测试所得到的基频与5个国家基本周期的经验公式估计值进行对比分析。

Natural frequencies and modal shapes of high-rise buildings, obtained from on-site ambient vibration test and operational modal analysis, are very important for evaluation of structural dynamic performance and seismic design. In this paper, a dynamic test project of Guangxi Laibin high-rise buildings was introduced. In this project, 8 high-rise buildings were selected for ambient vibration test to obtain the basic time history signals, then the cross correlation function analysis and fast Fourier transform were utilized to generate cross power spectra, from which the modal parameters such as natural frequencies can be obtained by operational modal analysis. Finite element （FE） models were constructed in PKPM and Sap2000 programs to calculate analytical modal frequencies and mode shapes. In order to consider influence of mass and stiffness of the in-filled wall on the dynamic properties of the high-rise buildings, 3 FE models were built in Sap2000 to estimate modal frequencies and modal shapes. It was found that the measured fundamental frequency is twice larger than that obtained from PKPM analysis. In addition, the structural modes obtained from the FE analysis, which uses shell elements to simulate mass and stiffness contribution of the in-filled wall to the corresponding beams, agree well with those obtained from the test. Finally, the frequencies of the 8 high-rise buildings obtained from the tests were compared with those calculated by the empirical equation in 5 countries.