Vibration Testing at Meazza Stadium: Reliability of Operational Modal Analysis to Health Monitoring Purposes
Vibration Testing at Meazza Stadium: Reliability of Operational Modal Analysis to Health Monitoring Purposes
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DOI：
10.1061/(asce)0887-3828(2008)22:4(228
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发表时间：
2008-08
影响因子：
2.5
通讯作者：
A. Cigada;A. Caprioli;M. Redaelli;M. Vanali
中科院分区：
文献类型：
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作者：
A. Cigada;A. Caprioli;M. Redaelli;M. Vanali
在过去的几年里，人们对与人民的安全和保障有关的所有专题的兴趣与日俱增。对容纳许多人的大型民用建筑，如高层建筑和体育场馆的健康监测给予了特别关注。一些非同寻常的事件，如伦敦的千禧大桥由行人激发的振荡，或在Ullevi体育场举行的Bruce Springsteen音乐会，从人群中协调跳跃对结构造成了严重破坏，并促使人们注意到更深入、更仔细地研究与土木结构的动态行为及其与人群的相互作用有关的所有问题。除其他外，对这些主题的研究还旨在开发允许对结构进行连续监测的技术，从一组可以一天24小时连续执行的测量开始，而不需要停止结构的功能。大量的科学文献证实了将结构健康与模态参数的演变联系起来的可能性，通常可以达到定位任何最终损伤的目标，否则使用不同的技术是不可能完成的任务。这篇文章展示了米兰理工大学长期项目的一部分，该项目是在米兰的G.Meazza体育场建立永久的健康监测系统。该项目的目的是评估构成体育场看台的结构的实际健康状况，并部署一个永久性监测系统，以记录每次活动期间所有子结构达到的振动水平。实际结构状态的评估是通过使用环境振动来进行的，这也与传统的实验模态分析进行了对比，实验模态分析是通过使用液压执行器提供的惯性力和详细的测量网格来执行的。这提供了利用所有可能的关于固有频率、振型和阻尼系数的信息的机会。这项任务非常耗时和昂贵，因此不能经常重复。因此，使用来自即将安装的永久监测系统的数据的可能性是改进结构诊断的一个有吸引力的前景。预计使用工作模式分析技术将意味着不需要对应用于结构的激励的知识。通过这种技术获得的参数估计通常会受到扩散的影响，既有所采用的识别技术的不确定性，也有外部参数的影响，如人群负荷或温度。由于损伤识别与模态参数的变化有关，因此对其正态分布的评估是确定阈值以识别可能的令人担忧的情况的基础。本文对米兰梅阿扎体育场3°环的主看台之一的模态参数估计中的分布进行了识别，并对一年多来收集的数据进行了分析。振动数据在不同的活动期间被记录下来，例如足球比赛和音乐会。所考虑的数据来自一组传感器，类似于将为永久监测系统安装的传感器，以检查将监测系统用作结构诊断工具的可能性。还进行了一项研究，以确定传感器选择和放置的关键方面，以便提供有关永久性监测系统设计的有用信息。本文的结果可以用来确定结构的可信度区间，在这个区间内，模态特性的变化可以被认为是异常的，因此，值得深入研究以评估结构的完整性。
In the last years an increasing interest has been devoted to all the topics related to the security and safety of people. Particular attention has been paid to health monitoring of large civil structures hosting many people, such as high-rise buildings and stadiums. Some extraordinary events, such as the Millennium Bridge oscillations in London, excited by pedestrians, or the Bruce Springsteen concert at the Ullevi Stadium in which coordinated jumps from the crowd caused serious damage to the structure, and drew attention toward a deeper and more careful study of all those problems related to the dynamic behavior of civil structures and their interaction with crowds. Research on these topics is also aimed, among others, at developing techniques allowing for a continuous monitoring of the structure, starting from a set of measurements that can be performed continuously, 24 h a day, without the need to stop the structure's functionality. The vast scientific literature confirms the possibility of relating structural health to the evolution of modal parameters, often reaching the aim of localizing any eventual damage, a task otherwise impossible with different techniques. This paper shows part of a long lasting project involving Politecnico di Milano in the setting up of a permanent health monitoring system at the G. Meazza Stadium in Milan. The aim of this project was the evaluation of the actual health state of the structures constituting the stands of the stadium and the deployment of a permanent monitoring system to record the vibration levels reached in all substructures during each event. Evaluation of the actual structure condition was performed by the use of ambient vibration, which was also checked against traditional experimental modal analysis, performed by using an inertial force given by a hydraulic actuator and a detailed measurement mesh. This offered the chance to exploit all possible information concerning natural frequencies, modal shapes, and damping factors. This task is extremely time consuming and expensive, therefore, it cannot be repeated very often. The possibility of using the data coming from the permanent monitoring system, which is about to be installed, is then an attractive perspective to improve structural diagnosis. It is expected that using operational modal analysis techniques will mean knowledge of the excitation applied to the structure will not be required. The parameter estimation obtained by this technique is usually affected by a spread, given both by the uncertainty of the adopted identification techniques and the influence of external parameters, such as crowd loading or temperature. As damage identification is related to changes of the modal parameters, the evaluation of their normal spread is fundamental to fix a threshold in order to identify possible worrysome situations. This paper deals with the identification of the spread in the modal parameter estimation of one of the grandstands of the so-called 3° ring of the G. Meazza Stadium in Milan, performed analyzing data collected over more than one year. Vibration data have been recorded during different events, such as soccer matches and concerts. The considered data came from a set of sensors similar to that which is to be installed for the permanent monitoring system, to check about the possibility to use the monitoring system as a diagnostic tool for the structure. A study was also carried out to identify critical aspects in the sensors' choice and their placement, in order to provide useful information about the design of the permanent monitoring system. The presented results can be used to determine confidence intervals out of which changes in the modal properties can be considered anomalous, and so, worthy of being deeply investigated to assess structural integrity.