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对某4层钢框架的非线性模态识别进行了试验研究和理论分析。利用单相谐波励磁给出框架的前两阶弯曲模态。随后对自由衰减振动进行了测量,并用于识别。开发初始筛选程序,以克服普通带通滤波器的缺点,并提高信号的准确性。将视在频率和等效黏滞阻尼系数自由衰减周期的变化作为自由衰减循环表观振幅的函数进行分析,通过以此建立的快捷程序进行结构的非参数识别。测定结果显示:在测量范围内,该结构刚度的非线性较弱、阻尼的非线性较强,而振型为线性。渐近非线性方法在包含模型刚度和阻尼的模态空间中定义,这是一种原创性的贡献。在时域中,提出的非线性模型与试验数据相符。拟合误差比纯线性模型低3个数量级。
The nonlinear modal identification of a four-story steel frame is studied experimentally and theoretically. The first two modes of bending of the frame are given by single-phase harmonic excitation. Free-decay vibration was then measured and used for identification. The initial screening process was developed to overcome the disadvantages of conventional band-pass filters and to improve signal accuracy. The change of apparent frequency and the free damping period of the equivalent viscous damping coefficient is analyzed as a function of the apparent amplitude of the free-decay cycle, and the non-parametric identification of the structure is performed by using the shortcut program established by this method. The measurement results show that in the measurement range, the stiffness of the structure is weakly nonlinear, the damping is strong, and the vibration mode is linear. Asymptotic nonlinear methods are defined in modal space that includes model stiffness and damping, which is an originality contribution. In the time domain, the proposed nonlinear model is consistent with the experimental data. The fitting error is 3 orders of magnitude lower than the pure linear model.