The Research On Train Multi-Axle Moving Load Identification Of A Bridge

In recent years, moving force identification from bridge dynamic responses under the action of vehicle axle loads has aroused extremely attention in academia at home and abroad. For so many methods for moving force identification, Bridge structures are acted as subjects investigated. With the development of technology, these identification ways have made satisfactory progress and formed a whole identification theory. This paper firstly established equation of motion of a simplely-supported beam subjected to moving loads. Based on the mode superposition method, an approach of moving load identification has been developed by using the least-squares method. Through numerical investigation, the cubic spline function is used to fit dynamic responses of bridge, and multiple moving constant loads on the bridge deck have been identified. Moreover, the effects of analytical parameters on accuracy of load identification are numerically studied and some useful observations can be made. Finally, the results indicate that the approximation method based on spline function is effective for the moving load identification of bridge. The algorithm is relatively simple and the identification performance is satisfactory.In chapter one, this article firstly introduces some existing methods which are used to identify moving load and the research situation in the inverse project both at home and abroad, and proposes a research goal and its significance in this foundation. Finally, the research target and contents are pointed simply.The second chapter presents some ordinary ways of moving force identification, and assesses and compares the advantages, disadvantages and scope of application related to these methods.The third chapter introduces the basic principle of moving force identification for bridge structure and the correlative knowledge about it, including mode shape orthogonality, mode superposition principle and so on.The fourth chapter introduces the feature of cubic spline function. The cubic spline function has a wonderful smoothness and can ideally fit the dynamic responses curve of a bridge. Meanwhile, by means of analytical software ANSYS of FEM, the model of bridge structure is built, and the dynamic responses of bridge can be obtained by editing corresponding commands of moving force. This chapter is a key part in moving force identification. Based on dynamic responses obtained from the analysis of ANSYS and moving force identification theory for brdige, a set of program used to identify moving force has been edited by utilizing the language of MATLAB, and the program can be run for the identified force. This chapter implements the identification of moving load. During the process of moving load, this chapter analyses the influence of the parameters such as the mode numbers, the numbers of point measured, the speed of moving force, some useful conclusions have been obtained.Finally, the fifth chapter summarizes the work in this paper, and it points out that as long as the parameters are suitably choused, the above method can effectively identify moving load on rail structure. Also, it points out the insufficiency of the method and views the next step of the research work.