不同刚度地铁地下车站结构振动台试验测试数据的时频特征分析

Seismic response characteristics of subway station structures with different stiffnesses based on time-frequency method

以模型结构整体剪切刚度量化微粒混凝土和石膏模型结构的刚度比,根据小波包变换的频带分布特征确定频带与结点的输出关系,并基于最小熵准则的最优基选择算法,对比分析了不同刚度三层三跨地铁地下车站侧墙加速度反应的时频特性。研究结果表明：最优小波包变换方法具有自适应的频域分辨能力,能较好地解决频带重叠现象。采用最优基小波包变换技术能有效挖掘出由结构材料不同引起的模型结构加速度反应的时间-频率-能量之间的差异。在强震作用下,微粒混凝土模型结构加速度反应的特征频带总能量高于石膏模型结构;石膏模型结构加速度反应在0~6.25 Hz频带的能量集中程度高于微粒混凝土模型结构,在〉6.25~12.5 Hz频带内的能量累积速率较微粒混凝土模型结构快;石膏模型结构加速度反应各特征频带进入快速能量累积的时刻均早于微粒混凝土结构。

The stiffness ratio of micro concrete to gypsum model structure was quantified by racking stiffness. According to the relationship between the node the and output frequency band of wavelet packet transform and minimum entropy based algorithms for best selection,the time-frequency characteristics of acceleration responses on sidewalls of different stiffness model structures were compared. The results showed that best wavelet packet transform could posesses recognition ability of frequency domain,it couldsolve the band overlapping phenomenon well. And it could excavate the difference of acceleration timeresponse’s frequency-energy distribution between different material models. Under the strong ground motion,special frequency band total energy of different acceleration response of micro concrete model were higher than that of gypsum model. The frequency band of 0-6. 25 Hz of acceleration responses of gypsum model structure was more concentrated than those of micro concrete model structure. Frequency band energy accumulation rate of gypsum model structure acceleration responses was faster than that of micro concrete model structure at 〉 6. 25-12. 5 Hz. The moment when frequency energy accumulated fast of gypsum model structure were earlier than that of concrete structure.