Damage Indentification Of Large-Span Continuous Rigid-Frame Bridge Based On Environment Encourage

Due to the increase of traffic volume, frequent occurrence of serious vehicle overloading and the other kinds of adverse affect, damages and destructions of long-span continuous rigid-frame bridges could be aggravated progressively. It greatly reduces the durability and the service life of the bridges. So during the operational life span of bridge, study of damage identification of bridge becomes significant. Under the background of the key projects of HuBei Province Education Department (No.D20111512) and W.I.T. science Research fund (No.13115085), this dissertation studied the subject, introduce a model updating method based on ambient excitation. To update the model of bridge, the first must accurately identify modal parameters. For large span bridge structure, the traditional modal test method was inefficient; The method based on environment excitation, that doesn’t need to know the input signal, can be carried out on the modal identification. Through the vibration test, use the method of power spectrum peak under environment excitation to get the modal parameters.Then, set up the FE model of the bridge, according to optimization theory,choose the high sensitive parameter to update. Finally, combined with an engineering example of a yellow River extra-large bridge, carries on the parameter type model updating. After the updating, the modal eigenvalues could preferably coincide with the measured values. That will make the stiffness distribution preferably match with the actual.The updated FE model could preferably be used for the following-up bridge structural damage identification, and could also provide theoretical guidance for preventive maintenance and health monitoring of the brigde. So the method has certain theoretical researching and engineering values.This paper mainly completed the following work: 1.Summarizes three kinds of damage identification method, dynamic fingerprint method, model updating method, genetic algorithm; Traditional modal parameter identification theory is expounded, then introduce the the advantages of modal identification method based on environmental excitation.2.Study the modal identification based on environmental excitation theory in detail, focuses on its peak power spectrum method.3. Systematically summarizes all aspects of the theory of model updating, such as the model error, the model condensation and extension, modification methods. Updating methods, including matrix modification method and the parameter updating method based on sensitivity, and then optimization theory is studied in detail.4. With the engineering example of a super major bridge in the Yellow River, establish finite element model, according to the modal data under ambient excitation,choose the high sensitive parameter to update. After the updating, the model can more accurately reflect bridge damage condition, so the method has certain practical value.