面向索网结构关键刚度监测的目标模态测试策略

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振动与冲击 ›› 2021, Vol. 40 ›› Issue (2) : 204-212.

论文

王新涛1,2，邓华1,2

作者信息 +

Target modes testing strategy for monitoring the key stiffness of cable net structures

WANG Xintao1,2,DENG Hua1,2

Author information +

文章历史 +

摘要

各种因素引起的预张力偏差将导致既有索网结构的刚度退化。通过测试少量的目标模态可以监测到索网结构关键刚度的变化；由于预张力偏差的随机性，最初根据索网理想(数值)结构模型确定的目标模态会在其所处的密频区内发生模态跃迁、局部化等变化；如仅依据这些理想的目标模态进行动力测试，将会降低对实际结构关键刚度偏差的监测精度；利用矩阵摄动理论，指出实际结构的目标模态振型可以表示为同一密频区内理想结构模态振型的线性组合。针对密频区内理想结构的每一阶模态，进行阶跃激励优化并抑制该频率区域内其它模态的振动；证明只要将这些优化后的阶跃激励荷载逐一施加到实际结构上，则该密频区内所有目标模态的振动可被充分激发，从而保证了其识别精度；利用识别到的目标模态参数计算出实际结构在主控荷载下的静力位移，便可实现对关键刚度变化的评价；借助一个马鞍形索网结构算例，对引入预张力偏差后的结构进行目标模态测试以及关键刚度评价，计算结果验证了该方法的有效性。

Abstract

The pretension deviations caused by various factors lead to the stiffness degradation of existing cable net structures.The key stiffness variation of a cable net structure can be monitored by testing and identifying a small number of target modes.Due to the randomness of pretension deviations, a target mode primarily determined based on the idealized (numerical) cable net structural model will change due to the mode jumping and mode localization in its dense-frequence region.Therefore, the key stiffness of an existing structure will not be accurately monitored if the dynamic testing is only based on these idealized target modes.By virtue of the matrix perturbation theory, the mode shape of the existing structure was expressed as a linear combination of the idealized mode shapes in the same dense-frequency region.For each mode of the idealized structure in the dense-frequency region, the optimization of step excitation loads was carried out to suppress the vibration of other modes in the same frequency region.It is proved that the target modes of the existing structure can be effectively excited if these optimized step excitation loads are applied to the structure one by one, thus their identification accuracies will be guaranteed.The identified parameters of the target modes, were utilized to calculate the static displacement of the existing structure, which was then employed to evaluate the variation of the key stiffness.The validity of the proposed method was verified by identifying the target modes and evaluating the key stiffness of an illustrative saddle-shaped cable net structure with pretension deviations introduced.

导出引用

王新涛1,2，邓华1,2. 面向索网结构关键刚度监测的目标模态测试策略[J]. 振动与冲击, 2021, 40(2): 204-212

WANG Xintao1,2,DENG Hua1,2. Target modes testing strategy for monitoring the key stiffness of cable net structures[J]. Journal of Vibration and Shock, 2021, 40(2): 204-212

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