Investigation Of Dynamics Model Updating Method Based On FRF

Currently, dynamic Modeling of the structure can be divided into two broad categories:One is experimental model, the benefits of such a model is more in line with the real situation, but it is limited to small-scale low-level structure, and experimental modal is usually incomplete and the impact of the noise can not be ignored, the cost is higher for large structures; another is finite element model, this kind of model's advantages are lower costs, easier changes, but it will bring modeling error. Integrated model updating technology of two kinds of modeling methods is rising, and becomes one of the most important directions in current structure dynamics research.Through literature research, this article sums up some major issues and research focus of the current model updating technology : (1) both experimental measurements and modal analysis exist errors, and the updating results have been significantly impacted by them; (2) incomplete measured mode shapes bring in the matching problem of degrees of freedom, common model reduction methods will lead to the physical meaning of matrix is not clear; (3) the current correction method applied to some simple structure proved to be effective, but for large complex structures have limitations.To resolve these above problems, this paper focuses on the model updating method based on the frequency response function, firstly, a kind of parametric model updating method based on FRF which didn't depend on sensitivity analysis was deduced, through the expansion of modal expansion model updating method, and uniting the idea of iteration, then presents an iterative expansion model updating on FRF (IEMUF) method. Through modified a riveting plate model of complex connection forms, the results show that this method has higher accuracy for the structure of common connection modeling error, and can effectively identify the location and extent of modeling error. This article also focusing on structural health monitoring Benchmark structure, identify Benchmark damage mode by the model updating method, results show that this method also has very good modification and identification of effects for complex steel structure model .In chapter 1, introduced the finite element model updating of the engineering background and research significance, an overview of the study model modification status and existing problems, this paper describes the main research contents and arrangements.In chapter 2, described the matching concept of degrees of freedom and several commonly used matching methods, and introduced the finite element model updating method based on FRF, then combined the expansion method of experimental DOF with model updating method, then presents an iterative expansion model updating on FRF (IEMUF).In chapter 3, for example, a riveting plate model of complex connection forms, for the common structure of existence of joints modeling errors, using the method proposed in this paper for model updating, and analyzed the applicability of method, and compared the effect of results with a representative IRS model reduction method.In chapter 4, described the ASCE SHM Benchmark problem and Benchmark test, and selected the appropriate condition, verified the feasibility of applying to the complex structure for the IEMUF method.In chapter 5, using the method proposed in this paper, updated the finite element model of the Benchmark, using the relevant parameters of the change to identify the location and extent of damage, and compared the results of domestic and foreign scholars, verified that the presented method has wide range of applicability for complex structures under the varying damaged conditions.In chapter 6, the main point of the research work and innovation in this paper were summarized, and made an expectation for the future study directions and contents.