Damage Identification For Long-Span Cable-Stayed Bridge Based On Modal Updating

With the vigorous development of transportation in our country, some long-span and super long-span bridges have been built one after another, and more and more attention are paid to the safety, durability and normal usages of these bridges. Based on the project of Baoding Cable-stayed Bridge, this thesis discusses the health monitoring strategies in accordance with the project, verifies the damage detection method which is used to assess the whole function of the bridge and provides basis for health monitoring in later period.Firstly, in the thesis,,it presents the situation and development of bridge health monitoring system. Based on the purpose and function of the health monitoring system, the health monitoring system components, monitoring substances, disposition of the monitoring sensor as well as the damage detection methods are identified. According to the project of the Baoding Bridge, a very bridge health monitoring system is founded. The field ambient vibration tests on the bridge deck and all stay-cables are conducted with DASP2000,a large dynamic signal analysis software. The signal data is analysis and compared with the theoretical value, then the damage level and position of the bridge can be ascertained. The plane and space finite element modals of bridge are built with ANSYS,the universal finite element analysis software, using optimization method. The modal is modified by utilizing the sensibility technique and the data of the dynamic characteristics of the bridge that have been measured on the spot, in order to imitate practical statement best. Then the static and dynamic analyses are performed and the cable and girder damage are intimated for the purpose of finding the relationship that brought to the structure displacement, internal force and dynamic properties. Modal curvature method is used to identify the damage level and site of the theoretical modal. Finally, associated with Baoding Bridge, using the methods above, a finite element is founded and updated, damage is detected as well.The results of the research indicate that the calculation model of the cable-stayed bridge set up in the thesis is applicable to the structural analysis. The research successfully proved that the modal curvature method can be used in the practical bridge damage detection. The thesis aims to provide guide for the similar bridge projects in the future and promotes their applications further.