Target modes testing strategy for monitoring the key stiffness of cable net structures
WANG Xintao1,2,DENG Hua1,2
1.Space Structures Research Center, Zhejiang University, Hangzhou 310058, China;
2.Zhejiang Provincial Key Laboratory of Spatial Structures, Hangzhou 310058, China
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.
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. JOURNAL OF VIBRATION AND SHOCK, 2021, 40(2): 204-212.
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