Research On Condition Assessment Of Existing Bridges And The Maintenance Managing Method

With the program of "online safety monitoring and management information system of principle road, bridge and tunnel in Hangzhou" as background, this paper has carried out the research on the health monitoring and danger alarming of the Zhong Bei Bridge. Sensor's installation plan and the alarming value are determined, as well as the influence of temperature changes to warning values.Bridge assessment index systems of different bridge types are analyzed and detailed. The concept of fuzzy is introduced to bridge condition appraisal, and traditional evaluation scale is replaced with triangle fuzzy numbers. The fuzzy analytic hierarchy process is taken as the basic method of bridge condition assessment. Top-layer fuzzy judgment matrix is calculated by the multi-level fuzzy transformation, and bridge condition mark is obtained.The fuzzy expense is proposed to represent the bridge maintenance cost, and the formula is got through the method of fuzzy synthetic evaluation. The declining bridge performance caused by time-variable factors is analyzed, and the fuzzy appraisal set in future is forecasted by two methods: Markov method and the neural network method, which provide an approach to forecast maintenance costs. Under the concept of LCCA (life cycle cost analysis), the influence of interest rate to maintenance cost is considered, and the cost formula is given. Finally, the cost formula considering both time-variable factors and interest rate changing is calculated.The bridge maintaining system is divided into two levels: the network-level and the project level, so as to analyze their respective research contents and focus. A composite index sorting method suitable to bridge maintenance decision making is proposed and applied in a network. Furthermore, by applying the P Norm Theory, a kind of quantification method to judge the maintenance priority is developed based on Euclidean Distance. Mathematical model of maintenance planning is proposed, taking into account the request of both the highest average condition ranking and the least total maintenance cost. Then, the model is simplified to a linear integer optimization programming with restraints, and is worked out by using genetic algorithm method. A kind of unique chromosome encoding method, which is simple and has rich meanings, is developed. Then the computational program is carried out by Matlab to solve the optimization programming.At the end of this paper, key points to make the guidelines of bridge health monitoring, controlling and maintenance programming are summarized.