A method to identify modal parameters of a large-scale bridge using structure ambient vibration responses was proposed. The method was based on bandwidth-restricted empirical mode decomposition (BREMD) and stochastic subspace identification ( SSI). Firstly, several intrinsic mode functions ( IMFs) only representing one frequency component respectively were obtained with EMD, then SSI was used to identify modal parameters. For the modal features of lower natural frequencies and being closely spaced of a large-scale bridge, a masking signal was introduced to restrict the EMD bandwidth to eliminate mode mixing. The method was used to identify modal parameters of a large bridge of Gan-Long rail, and the results were compared with those of the peak-picking method, SSI and finite element analysis, they showed that the proposed method can effectively identify large-scale bridge modal parameters, the induction of masking signal solves the problem of mode mixing in EMD, and the false modes in stabilization diagram are suppressed.%提出一种依据环境激励下结构振动响应的大型桥梁模态参数识别方法,该方法以限制带宽的经验模态分解(BREMD)和随机子空间识别(SSI)为基础,首先利用EMD将环境振动响应分解成一系列只含结构某一阶固有模态的本征模态函数(IMF),然后利用SSI识别桥梁模态参数.针对大型桥梁自振频率低、模态密集的特点,引入屏蔽信号限制EMD过程中带宽以消除模态混叠;运用该法识别了赣龙铁路某特大桥的模态参数,并将其与峰值拾取法、SSI识别结果以及理论计算值进行对比,结果表明:该方法能有效的识别大型桥梁模态参数,屏蔽信号的引入解决了模态混叠问题,稳定图中的虚假模态得到抑制.
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