Study On The Structural Damage Identification Based On The Information Fusion

During the servicing period of engineering structures, due to various complicated factors such as natural environment and various disasters etc, the structure will suffer different degree of damage. Therefore, the structural damage identification, evaluation and repairing has great significance to the loss of lives and properties .To improve the accuracy of the damage identification and robustness,The structure damage identification methods based on the changes of stiffness and the mode strain energy ,and the D-S evidence theory and the Bayes theory in the information fusion technology have been used to structure damage identify of plane truss structure and offshore platform . The main content of the thesis includes:(1)Four structure damage detection methods based on the changes of stiffness and mode strain energy, the D-S evidence theory and the bayes theory are presented respectively, and the former is improved. Stiffness damage factor iterative method is proposed to identify damage.(2)The structure damage identification method based on the changes of stiffness is used to identify the single and multiple damages about the numerical model of a plane girder and the numerical model and the experimental model of an offshore platform with the first three modal parameters, and the influence of noise is considered too. Results show that the method is better for plane truss structure, but for the offshore platform, misjudgment is easy to appear.(3) The damage identification method based on the mode strain energy is used to identify the single and multiple damages about the numerical model of a plane girder and the numerical model and the experimental model of an offshore platform with the first three modal parameters, and the influence of noise is considered two. The results show that the effect of the method is good for plane truss structure, but for offshore platform, because of the incomplete modal information and the experiment errors, misjudgment is easy to appear.(4)In order to overcome the disadvantage of misjudgment of single damage identification method,the D-S evidence theory is used to fuse the structure damage identification reasults from the methods based on the change of stiffness and mode strain energy. From the results of numerical simulation and experiment, we can see that compared with single source, using D-S information fusion method that synthesizes the results of the two methods intelligently, can produce more accurate and more complete estimation and judgment. The noise error and incomplete information are reduced in a certain extent by this method.(5) The normalized identification results of the stiffness damage factor iterative method and the damage identification method based on the mode strain energy are considered as their conditional probability by the structure damage identification methods based on the bayes theory, which has been used to identify the structural damage, assuming that the damage conditional probability of the identified elements is equal. The results of numerical simulation and experiment show that the method improves the accuracy and reliability of the structure damage identification, and has strong robustness to noise. The identification results are similar to that of the structural damage indentification method based on D-S evidence theory.