Based On The Generalized Distance Of A Large Bridge State Assessment Study

With the advancement of society and the development of civil engineering techniques, more and more large bridges have been constructed. In order to ensure the security and endurance match expectable objective, health monitoring and condition assessment for large bridges is more significant than ever.The work in this thesis is focused on a condition assessment based on generalized distance and processing the data by principal component analysis (PCA) method. The main contents are detailed as following:(1) Review state of arts of the condition assessment of large bridges. The essential ideas, contents, theory elements of the condition assessment and common method used in bridge condition assessment are systematically introduced. The problems and development trends of the condition assessment of the bridges are summarized.(2) Complete transient dynamic analysis in the whole course of train's passing through, after programming the measured train axle loads from Nanjing Yangtze River Bridge (NYRB) monitoring system to the nodes of longitudinal girder as a set of moving concentration loads with constant velocity, and the train axle weight as mass element on the corresponding nodes. The calculation model of NYRB is considered as a time-varying system in the course of analysis.(3) Based on the generalized distance propose a condition assessment method for the overall evaluation of NYRB. The weights of measured points of Nanjing bank are evaluated by utilizing analytic hierarchy process (AHP). Based on the platform of MATLAB, the working condition information of the Nanjing unite is to be analyzed by the degree of membership so as to evaluate the working condition.(4) Calculation and evaluation need a large amount of work because of so much monitoring data for a large bridge. Taking Nanjing unite as an example, PCA can be used to process the monitoring data and obtain the condition of the whole bridge with the least data information so as to simplify evaluation work. Comparing with the results before and after data processing, the obtained evaluation results are consistent. So, this method is effective.(5) Utilize ANSYS software to make simulation analysis of Nanjing unite on the assumption of some members damaged. Then the condition of Nanjing unite is evaluated by using the method proposed in this thesis. The results show that the condition assessment method based on the generalized distance can effectively reflect the working condition of bridge, and is a feasible method of condition assessment.