Research On Bridge's Damage Detection And Evaluation Based On Static Test Data

In order to correctly judge whether the damaged structure could be continuously used or need to be reinforced, how to evaluate the remaining capacity and reliability of the damaged structure, is nowadays a new problem which must be studied in civil engineering. Obviously, in order to solve this problem, the premise is that the properties of the damaged structure must be actually evaluated. The main purpose of damage detection is to estimate the actual properties of the structure and assess its reliability, In this thesis, supported by a research project "Damage Detection of Bridge Structure from Static Measurements" sponsored by science and technology fund of Southwest Jiaotong University(2003A14), the author carries out systematic researches on the theories of structural damage detection and evaluation based on static test data. And according to the static test data from the research project "The Test Study on Externally Prestressed High Strength Concrete Continuous Beam " sponsored by the Doctoral Program of Higher Education(98061307), the damage detection of four test beams is conducted. The thesis includes four parts:In the first part, the author carries out the researches on the choice of the baseline model for damage detection, the damage parameters and the algorithm for parameter identification. Firstly the basic principles of the choice of the baseline model is discussed. Considering the specific characteristic of the bridge structures, the author believes that, the FEM model of the three dimensional bars, especially suitable for controlling the number of test data and the number of identified parameters, could be keeping with above principles. Therefore it is a good baseline model for the damage detection of the bridge structures. Starting with the Counter-question of the mechanics, the author counts damage detection to the problem of the system parameter identification and uses the relative residual error vector of the static displacement to construct the criterion function of the least squares method, and adopts constrained optimization method to identify the damage parameters. From the viewpoint of structural damage detection, for each element of the model, only one parameter is needed to distinguish whether the element damaged or not and assess the extent of the damage. Therefore the author selects the reduction factor of stiff-reduction factor of stiffness as the only damage parameter to be identified.In the second part, the author carries out the researches on the damage detection method under the rarely test data and the test error. To the large complicated structures, it is a contradiction between the scarcity of test data and the large quantity identified parameters of the structure. How to resolve it is a key problem within the damage detection. The parameter grouping algorithm is a good selection at present. The author brings up a damage area detection method of the bridge structures in line with the parameter grouping algorithm described in the reference literatures. This method is deduced in detail and its reliability is verified through the example analysis. The damage detection of large complicated structures taking the uncertainty into account is paid a widespread attention in the domestic and international academic and engineering field at present. Firstly, based on the probability and statistics theories, stochastic FEM parameter model of the structure is established to study the effect of the test error on the damage detection results. According to hypothesis test theories, whether the prior distribution of the parameter is known or unknown , the damage location criterion is studied systematically. The index of damage location is brought up based on this criterion. And thirdly , according to the assumption of normal distribution of the parameters, the index of damage degree is defined too. In order to calculate the index of damage degree based on the damage probability, the relationship between them is established. It makes the damage degree assessment have the probability meaning. Finally, The influence caused by model error to the damage detection is analyzed. The revision of the structural model error is counted to the process of damage detection under the specific condition. So the probability evaluation method is applied to revise the structural model error margin.hi the third part, the author carries out the researches on the theories of structural reliability and remaining life prediction. The traditional theories are based on the geometrical, physical properties of the component's section derived from the local detection method. But the author, according to the results of the damage parameter identification directly, tries to establish the assessment theories of the structural reliability and remaining life prediction completely based on the viewpoint of the damage detection.hi the fourth part, the author applies the above theories to assess the damage of...