单输入多自由度系统自然激励技术的解析格式

Analytical Scheme of Natural Excitation Technique for Single Input Multi-Degree-of-Freedom Structural Systems

自然激励技术的提出为大型复杂工程结构环境激励下的模态提取提供了一条新的途径,但对于单输入的情况存在以下问题:白噪声激励下结构系统位移响应的互相关函数公式中的相位角和幅值缺乏解析表达式;当动力荷载恰好作用在系统某阶振型的节点时可能出现的现象缺乏分析和物理解释。发展了单输入自然激励技术,推导了白噪声激励下结构位移响应的互相关函数,给出了其中相位角和幅值的解析表达。研究发现,当单输入动力荷载恰好作用在系统某阶位移模态的节点时,任意两自由度位移响应的互相关函数中将不含有频率值等于该阶模态有阻尼固有频率的简谐成分,即该阶模态的信息在互相关函数中得不到反映。

Natural excitation technique(NExT)has provided a new approach for modal parameter identification(MPI)of large complicated structures using operating ambient excitations.The original NExT for single-input multi-degree-of-freedom structural systems still has some theoretical deficiencies:for the case of white noise excitation,the analytical formulas of phase angles and amplitudes need to be derived in the displacement cross-correlation function,and the theoretical interpretation is unclear when the dynamic load acts on a modal node.The analytical formulae of phase angles and amplitudes in the displacement crosscorrelation function are derived,and it has been discovered that when the dynamic load acts on a modal node,the cross-correlation function would not contain the decaying sinusoid component whose frequency equals to the damped natural frequency of the corresponding structural mode.