Damage Diagnosis Identification For Post-Earthquake Bridge Structurebased On HHT And SVM

Earthquakes emerged in China are frequency, intensive and extensive, and most of them occur at a very shallow stratum. Bridge Structure is mostly prone to be damaged in the above mentioned earthquake. Nonlinear and nonstationary excitation on the bridge structure is the outcome of the earthquake motion with intensive energy; therefore the responses of bridge structure are also nonlinear and nonstationary. Furthermore, the structural state is specified by time-dependent and nonlinear. The damage of bridge structure induced by the earthquake is different as compare to other kind excitations, thus there are particular features for the bridge structural post-earthquake damage diagnosis identification. The damage diagnosis identification on post-earthquake bridge structure is regarded as the objective, the following tasks has been discussed, in combination with the OpenSees, Hilbert-Huang Transform of Time-frequency signal analysis theory and the Support Vector Machine method of Statistical Pattern Recognition:1. The nonlinear seismic response of the bridge structure with the finite element model is discussed.2. Based on the seismic vulnerability analysis, the main seismic wave which can make bridge structure damaged are selected and this acts on the bridge to make the damage occurred, meanwhile different intensities indicate different damage cases. Then the responses of damaged bridge structure under the excitations of a number of aftershock waves have been collected to carry out the damage warning and the damage location for the post-earthquake bridge structure.3. The results obtained from the seismic vulnerability analysis shows that, the vulnerable area and its location can be identified, thus can be used as the instrument for damage location. Then based on the accelerometer locations and referencing the real earthquake situation, HHT theory was applied to obtain the sensitive damaged index of Time-frequency domain, and SVM method was used to identify the damage on post-earthquake bridge structure by two steps.4. Finally a certain long span continuous rigid frame girder bridge with high pier is analyzed by the proposed method. The result shows that it is effective and feasible in identifying the damage location for real life bridge structures.