Experimental Study on Damage Identification of Dynamically Excited Structures

摘要土木工程结构在地震、风荷载和其他荷载作用下，基于振动数据的损伤检测、定位和定量分析越来越受到人们的关注。早期的动机是由1994年北岭地震和1995年科比大地震造成的钢结构隐藏损坏的发现，以及结构元件通常在施工后无法接近的事实提供的。在文献中已经提出了几种分析方法，还有更多的方法正在开发中，目前正在使用模拟数据来检查这些方法的有效性;本课题拟通过实验研究和验证具有外生输入的自回归模型、小波变换特征系统实现算法（ERA）和子空间识别（SSI）方法用于土木工程结构的综合模态和损伤识别。对于损伤定位和量化，将使用有和没有损伤定位矢量的柔度和转动柔度矩阵.这些方法的进一步分析改进也将有助于更可靠的损伤定量。试验将在一个三层、九自由度的结构模型上进行，该模型的刚度特性可以通过一个或多个支撑的计划变化、使用磁流变阻尼器实时突然移除一个或两个支撑以及在少数选定的接头处松开连接硬件来改变。制作这个可变比例模型的主要费用将由私立学校承担。比例模型将在其基础上激发的5'乘5'振动台在AtominiaTech。该模型也将有能力被激发的振动器安装在任何三个层次。加速度响应的动态测量将使用十个加速度计，三个放置在每个楼层的两个正交方向上，另一个放在桌子上。SGER基金正在寻求确定有效的损伤定位和量化方法，这将需要在一个更全面的后续研究。随后提出的后续研究将开发一个集成系统，该系统包括有效的损伤识别技术，在线后果预测，然后在线驱动，如果必要的话，控制系统将结构的性能保持在可接受的水平。这项探索性工作的成功结果也将是一个非常有用的工具，直接实际实施的结构诊断和健康监测。本研究的智力价值是在实验验证的损伤识别的发展（检测，定位和量化）方案的综合结构健康监测。更广泛的影响，这项研究将发生在两个层面：研究生和本科生的教育和培训，以及为参与结构健康监测的研究人员和从业人员提供急需的工具和数据。一名研究生和一名本科生将从事这个项目。本科生将通过REU计划获得支持。她/他将通过弗吉尼亚理工大学工程多样性增强中心（CEED）从非洲裔美国人，西班牙裔，美国印第安人和女学生中选出。本研究中产生的信息和数据将通过课堂教学、网站创建、会议演示以及在档案期刊和会议论文集上发表来传播给其他学生、研究人员和出版商。

AbstractThere is an increasing interest in the vibration data-based detection, localization, andquantification of damage in civil engineering structures exposed to earthquake, wind, and otherloads. Early motivation for this was provided by the discovery of hidden damages in steelstructures caused by the 1994 Northridge and 1995 Great Hanshin (Kobe) Earthquakes, and alsoby the fact that structural element are usually inaccessible after construction. Several analyticalmethods have been proposed in the literature and still more are being developed for this.Currently simulated data are being used to check the effectiveness of these methods; however,their validation and comparison on actual experimentally obtained data is yet to be done.In this exploratory project, it is proposed to experimentally study and validate theeffectives of the autoregressive with exogenous input model, wavelet transform, eigensystemrealization algorithms (ERA), and subspace identification (SSI) approaches for comprehensivemodal and damage identification of civil engineering structures. For damage localization andquantification the flexibility and rotational flexibility matrices with and without and damage locatingvectors will be used. Further analytical improvements in these methods will also be made formore reliable damage quantification. The tests will be conducted on a scaled three-story, ninedegrees-of-freedom structure model prepared such that its stiffness properties can be changedby planned changes in one or more braces, by sudden removal of one or two braces in real-timeusing magneto-rheological dampers, and by loosening the connecting hardware at few selectedjoints. The major cost of preparing this changeable scaled model will be borne by the PIsinstitution. The scaled model will be excited at its base by the 5' by 5' shaking table at VirginiaTech. The model would also have the capability of being excited by shakers installed at any ofthe three levels. The dynamic measurements of the acceleration response will be made usingten accelerometers, three placed at each floor level in two orthogonal directions plus one on thetable.The SGER funding is being sought to identify validated damage localization andquantification methods which will be needed in a more comprehensive follow-up study. Thisfollow-up study to be proposed later will develop an integrated system consisting of the validateddamage identification techniques with online consequence prognosis followed by onlineactuation, if necessary, of a control system to maintain the performance of the structure at anacceptable level. The successful outcome of this exploratory work will also be a very useful toolfor direct practical implementation in structural diagnostics and health monitoring.The Intellectual merit of this study is in the development of experimentally verifieddamage identification (detection, localization, and quantification) schemes for a comprehensivestructural health monitoring.Broader impacts of this research will occur at two levels: theeducation and training of graduate and undergraduate students and the availability of a muchneeded tool and data to researchers and practitioners involved in structural health monitoring. Agraduate student and an undergraduate student will work on this project. The undergraduatestudent will be supported through the REU program. She/he will be selected through the Centerfor the Enhancement of Engineering Diversity (CEED) at Virginia Tech from the pool of availableAfrican American, Hispanic, American Indian, and women students. The dissemination ofinformation and data generated in this research to other students, researchers and practitionerswill be done through class room teaching, website creation, presentations in conferences, andpublications in archival journals and conference proceedings.