Health Monitoring Of Tied Arch Bridges Based On The Urban Bridge Cluster Monitoring System

In recent years, with the rapid urbanization process and increased accidents of bridge damage and collapse, the research of bridge health monitoring and early-warning technology for the public safety was been promoted. In order to achieve high performance of urban bridge service and security, this research has meets the requirement of the economic and social sustainable development, and becomes an urgent and important issue of both science and engineering.Urban bridge cluster monitoring system is an important part of the infrastructure informationization in the construction of digital city. Taking urban-traffic-corridor bridges as the study object, the system is applying the modern sensing, communications and information network technology to realize the integration and open-distributed network monitoring, which takes full advantage of the health monitoring system with real-time monitoring data collections and the bridge management system in a comprehensive assessment of bridge safety. It can also avoid the poor reproducibility and the lack of communication and integration with the single-bridge monitoring system, which easily forms the "isolated information island" and is unable to provide effective support for the protection of the urban bridge overall security. It's a new model of urban bridge maintenance and management with the background of city informationization.Tied arch bridges are commonly constructed and become more and more popular in the modern city, due to its beautiful structural esthetics, excellent capability of mechanics and economical cost-effectiveness. This thesis takes the development of on-line safety monitoring and management system (Phase II) of Hangzhou traffic corridor bridges as the engineering background to promote urban bridge cluster monitoring system development and implementation. The main research contents and innovation achievements are as follows:1. The cluster monitoring system was explored from the aspects of orientation, design principles, system architecture and implementation technology, meanwhile, according to the long-term plan of Hangzhou urban-bridge maintenance and management (2008-2020), the implementation during all the planning stages were discussed. The current monitoring system includes three crossed canal bridges, one elevated freeway, one cable-stayed bridge across the railway and one arch bridge across Qiantang River. The whole system was based on the VPN technology, realized the on-line monitoring of structural dynamic responses, and collected a great deal of valuable data to explore the actual safety state of various types of bridges in the operational phase. Hangzhou became the first city in China which established a unified online monitoring system for different types of bridges.2. Based on the urban bridge cluster monitoring system, the Yeqingdou bridge subsystem was studied focus on the following research contents:a) The online health monitoring subsystem of Yeqingdou Bridge was developed, which combined the characteristics of tied arch bridge with existing research of bridge health monitoring system. Based on the 1 year monitoring data, the corresponding data management rules were set up at first; then the automatic identification methods of single-point and continuous failure data was discussed respectively; finally, according to the statistical analysis of monitoring data, the daily and annual temperature variation patterns have been investigated, the correlation between the monitored structural responses and temperature were revealed, with the regression model. The temperature induced effects were eliminated from the total structural responses and improved the effectiveness of structural damage identification of the monitoring index.b) Based on the monitoring data analysis, the reference finite element model was established by means of updating the modeling error and the physical properties of the bridge structure, which improved the agreement that between the analysis results and the on-line monitoring data, and the thresholds of early warning indicators were calculate to realize the online alarming. According to the Analytic Hierarchy Process, the evaluation index system of tied arch bridge was established with the consideration of different assessment index effects on the bridge safety, serviceability and durability. The initial weights of each element and index assessment criteria were determined by combing the model analysis and monitoring data statistical analysis. Finally, the object of quantitative evaluation to bridge safety was achieved.c) The method of life-cycle maintenance strategy based on the criticality and vulnerability analysis with the consideration of tied arch bridge characters was proposed. Based on component rigidity criterion and sensitity analysis, the criticality components were determined and the relative importance of the structure members or possible schwachstelle was revealed. Meanwhile, by combining the structural theoretical analysis and on-site monitoring data, the capability-demand ratio was computed and the vulnerable bridge components were identified. Finally, the risk sequence of the tied arch bridge components was determined to guide the monitoring and maintenance strategy.In the end, based on the above studies, the problems and future development of the urban bridge cluster monitoring system were discussed.