基于局部主频率的子结构损伤识别研究与试验

针对大型复杂结构的整体监测常常面临测量信息不足等困难,提出只利用局部动态响应进行子结构损伤识别的局部主频率方法.子结构的局部主频率指：如果整体模态中含有以局部子结构位移为主的模态,即等价于在局部激励作用下,整体结构的振动主要体现为子结构的振动,并且主要以这阶局部模态振动为主,那么对应的该阶频率即定义为子结构的局部主频率.局部主频率主要反映子结构的局部特性,对子结构损伤的灵敏度高,所以只利用局部主频率就可以识别子结构.当子结构特征不明显时,提出通过附加质量使子结构具有局部主频率的有效方法.该文进行了大型空间桁架的局部动力测试试验,试验中通过附加质量使杆件子结构具有局部主频率,并能准确地识别出杆件损伤的位置和程度.

THE STUDY AND EXPERIMENT OF SUBSTRUCTURE DAMAGE IDENTIFICATION BASED ON LOCAL PRIMARY FREQUENCY

For huge complex structures, it is difficult to obtain enough information which is required necessarily in their global monitoring. Aiming at this problem, a Local Primary Frequency (LPF) method is proposed for a local damage identification using only a local measured response, which is easy to be performed in a real application. LPF belongs to the frequencies of a global structure, but the distortion of the corresponding mode mainly concentrates on a substructure under the local excitation and the subculture vibrates mainly in the form of this mode. In this way, the corresponding frequency is defined as the LPF of the substructure or it is said that the substructure has its LPF. Therefore LPF reflects more characteristics of the substructure and is sensitive to the local substructure damage, and hence only a Local Primary Frequency is enough to identify the substructure damage. However generally substructures don’t own their LPFs. Locating additional mass on the substructure is proposed as an efficient method to make the substructure have LPF. An experiment of a big space truss is used to verify the proposed method. Both the damage location and damage extent are identified accurately via the substructure LPF.