Modal Parameter Identification Of Bridge Structure Under Ambient Excitation

ABSTRACT:Civil engineering structures are prone to be damaged to some degree caused by all kinds of different loads from the environment during their service lives, which may become potential hazards and result in disastrous consequences. Thus makes it especially important to identify the structures’damage. And it has become a very hot research project to identify the structures’ damage by its dynamic characteristics. So the modal parameter identification methods is becoming the key problem.The modal parameters identification method of engineering structures is generally divided into traditional modal parameter identification method and modal parameter identification under ambient excitation. And compared to the first kind, the second one has lots of advantages, such as the low-cost, the less effect on the structures’normal working and having no need of artificial incentives. So this article begins the research from the study on modal parameter identification methods under ambient excitation.First, this article introduced the theoretical basis of modal analysis, then deduced two signal pre-processing methods (RDT, NExT) and four modal parameter identification methods under ambient excitation (ITD, STD, ARMA, SSI). Secondly, taking a continuous girder bridge as an example, do the transient analysis to obtain its time-histories data under three different ambient excitations. Then identify its modal parameters, compared them to the true ones, and verified the applicability of the algorithms. Thirdly, put different levels of noise into the time-histories data and do the same analysis to verify the anti-noise ability of the methods. And pick out the best method, SSI. Fourthly, combine the methods that this article mentioned with NExT, coming out the new modal parameter identification methods. Then do the same modal parameter identification, and verify its applicability, accuracy, and anti-noise ability under ambient excitation. Finally, we got the time-histories data from a bridge column experimental modal analysis. Then do the modal parameters identification of the bridge column with the new methods. Thus, the method of this article is used in a practice engineering project.