Model Test Research On Damage Detection For Bridge Structures Under Moving Loads

Damage alarming, damage localization and damage extent identification are three key problems of damage detection which have been studied by this research. Wavelet transform and Hilbert-Huang transform are commonly used for signal processing in time-frequency analysis while the support vector machine is for pattern recognition. These methods have already been introduced to the process of bridge damage detection by some researchers. Based on some existing results, research on bridge damage detection under moving loads is carried out. As a result, a series of efficient damage indexes are constructed. Meanwhile, corresponding methods for damage detection are proposed. The main works include:Firstly, state-of-the-art for damage detection under static loads and moving loads are summarized. Damage detection methods based on time-frequency analysis and on pattern recognition are reviewed, respectively. Moreover, problems of bridge damage detection under moving loads are discussed.Secondly, principles of wavelet transform and of Hilbert-Huang transform are expounded. Based on these two methods, different damage indexes for alarming, localization and extent identification are constructed and tested. After comparison, damage indexes used in this thesis are determined. The support vector machine is based on statistical learning theory. Principles of the two main parts, classification and regression, are discussed.Thirdly, research process of damage detection is pointed out. Details of methods used in this thesis are discussed in three main parts:damage alarming, damage localization and damage extent identification.Fourthly, by numerical simulation for a30m highway simply supported girder bridge, the validity and the anti-noise performance of damage indexes are tested in the three processes of damage detection. Two damage indexes are proposed for damage localization. The effects are compared specially.Lastly, based on the test data of a cable-stayed and suspension combination system bridge, effects of damage indexes are tested in the process of alarming and localization. After all, the feasibility of methods used for model test is researched.