Bridge Finite Element Model Updating Based On Dynamic Response Surface Of Combination Function

Finite element method has been widely and deeply applied in bridge structures of static and dynamic analysis, condition monitoring, identification and prediction. But, as a modeling method, it can be brought out without depending on the real structure, it was inevitable to make mistakes comparing to the real structure, which results the authenticity and accuracy of the analysis difficult to ensure. Therefore, it was necessary to update the finite element model reasonably in some way. This thesis is based on the structure finite element model updating technology. The deficiency that finite element model called frequently and large computing of the parametric type updating method was avoided. The bridge finite element model updating based on dynamic response surfaces was applicated in this study. In this thesis, the quadratic-gaussian function was constructed. Through various comparisons and different structural validations, the fitting ability and updating precision was improved, and the anti-noise ability was outstanding. The working was as follows:Firstly, the basic principle of the finite element model updating based on response surface was expounded in the thesis. Familiar types of response surfaces, fitting methods and optimization algorithms were concluded. The fitting abilities, anti-noise abilities and updating precisions in various of responses surface functions (linear-gaussian, quadratic polynomial, quadratic-gaussian, cubic polynomial) was compared based on the example of a simple supported beam. The advantages of the quadratic-gaussian function were shown.Secondly, a cantilever beam was designed and made, and the dynamic experiment was completed. Based on the result of the dynamic experiment, the objective function was solved through optimization algorithm by Matlab. The initial finite element model was updated. Through the modal analysis of the updated model, the validity of the updating was proved.Lastly, combined with a bailey steel bridge, the initial finite element model was established based on design drawing. The data of the dynamic test was the updating target. The initial finite element model was updated based on the response surface fitted by quadratic-gaussian function. The result of dynamic response analysis (dynamic deflection) of the updated model was consistent with the dynamic loading test. The validity of the method in the thesis used into engineering application of the complicated bridges was proved.