Study On Dynamic Load Identification Applications

Load cannot be measured in most conditions because of complexity of the structure and the load.So, it is necessary to inverse it from the response and the characteristic of the structure.This study has acquired outstanding achievements.The technology of points-load-identification are very better and better. However the technology of identification for structurally distributed load in succession is seldom.In this dissertation, The main work is to study the technology for distributed load identification.and establish identification models based on the moment method and wavelet method. Based on the vonvergence of basis function for moment method, A complex dynamic load to be identified is simplized by solving the coefficients of the orthogonal basis function. According to the linear principle, A general identification model is established in the software for finite element anaylsis. It includes all complex structure under arbitrary boundary conditions. The method possesses of the abilities of high identification precision, anti-interference and nonrestraint of the measure position. The feasibility and correctness of these methods are verified by testing instance and experiment. The primary contents are as follows:1. A moment method is applied to moving load identification. First three methods for establishing simple model are discussed for the coupling interaction system between vehicle and bridge .These simulating results generated by three methods are contrasted with each other and with experiment data, A conclusion is drawn that the two degrees of freedom model is best.Then the identification of moving load, A special distributed load, is studied in this dissertation, A general model for moving load identification is established on a base of the moment method and some shorcomings are overcomed.2. The basis functions for the moment method are defined in a two-dimension orthogonal space and used for identifying two-dimension distributed load. The two variables of the unknown load are fitted by the basis functions.A model in frequence domain is established for identifying two-dimension distributed load, acting on a complex constructure, in the finite-element-analysis software and it is verified by testing instance.3. Based on the ideas of the frequence domain method of a distributed load identificaition, A two-dimension distributed load can be identified directly in time domain by using three-dimension basis function to fit the three vaiable of unknown load.4. A problem is dicussed that how to reduce the number of measure points to identify the distributed load equally. A two-dimension distributed load can be equaled to the node loads in finite element model.when these node loads are arranged on a supposed axis, they can be identified by a one-dimension method, so the aim for reducing dimension can be reached. When these node loads on the supposed axes are arrayed in an optimized order, the fitting order can be reduced and the object of reducing the number of measure points can be reached. 5. The wavelet theory is introduced into dynamic identification and a model based on dynamic finite element is established for wavelet method whose correctness is verified by testing instance.6. The practical feasibility for these methods is verified by moving and distruted load experiment.