Health Monitoring System Design And Warning Threshold Study Of The Second Wuhu Yangtze River Highway Bridge

Bridge is the key infrastructure of highway and railway transportation, and it is also the key node of urban transportation network. With the rapid development of the theory of bridge analysis, construction technology and material properties, the bridge span and structure flexibility is growing. This requires the calculation and construction technology to be more sophisticated, and the safety of the bridge should be further improved. Using scientific and reasonable means to make sure the safety of the bridge has become a common understanding of the engineering staff.The Second Wuhu Yangtze River Highway Bridge is a full floating four cable planes and separated steel box girder cable-stayed bridge with a main span of 806 meters. The bridge is at the top of the world in the same kind of cable-stayed bridge. Aiming at the health monitoring system of the Second Wuhu Yangtze River highway bridge, the framework of health monitoring system of this bridge, the risk analysis based on finite element analysis, the overall design of health monitoring system and the determination of early warning threshold of monitoring index are studied. The research of this paper has important theoretical significance and engineering practical value. It also can provide basis for the design of the Second Wuhu Yangtze River Highway Bridge.The main research contents and conclusions of this paper are as follows:1. Combined with the research results of health monitoring and the practical application, the main principles which should follow in the design of long-span bridge health monitoring system and the main contents of the health monitoring system are summarized. The bridge health monitoring system is divided into five subsystems, and each subsystem is described in detail.2. In order to provide reference for measuring point layout of health monitoring system, finite element model of the Second Wuhu Yangtze River Highway Bridge is established and the risk analysis of girder stiffness degradation and different degrees of cable breakage are conducted. The results show that the damage of main girder and cable will lead to changes in the working state of the structure. At the same time the beam local stiffness changes has less affection to the bridge response, but the damage of the cable-stayed bridge has great influence on the overall response of the bridge.3. According to the result of the risk analysis and the finite element analysis, the monitoring project of the bridge is designed. The monitoring project includes the environment and the bearing load, the static response of bridge structure, the dynamic characteristics of bridge and other information. And the location of the measurement points of each monitoring project is arranged too.4. A finite element simulation analysis method is proposed to determine the warning threshold value of this bridge. The response of the bridge under the combined action of the load effect on the normal use limit state and ultimate limit state are calculated. The maximum values of the deflection of the main beam in two design limit states are obtained, and the two values are used as the first level and the second level warning threshold value of this parameter. According to the bridge response when the local component is damaged and the deflection is close to or reach the limit value of the standard deflection, it is determined that the limit value of the deflection of the bridge girder is third level of early warning threshold value.