Research On Methods Of Trestle Structural Modal Analysis Under The Ambient Excitation And Updating Methods

Security and comfort is particularly important for the construction. Therefore, it has a vital significance to make a further perfect combination of the safety, durability and comfort of buildings and structures. The traditional mode experiment methods are always hard to be achieved because it needs to be imposed an external excitation, or because the cost is high, or because it affects the normal use.This dissertation is based on the modal parameter identification under ambient excitation, so it doesn’t need the outside incentive and doesn’t affect the structure normal use. At the same time, it greatly reduces the experimental cost.In this paper, on the background of the scale model and the actual project, starting from the basic theory of vibration testing and modal analysis, single-layer latticed cylindrical shells scale model of ANSYS numerical simulation and ambient vibration tests and to bridge the theoretical modal analysis and experimental modal analysis and model correction ready to do the work.Firstly, under ambient excitation of single-layer latticed cylindrical shells vibration test based on, use random sub space method to calculate the dynamic characteristics of the single-layer latticed cylindrical shells such as frequency and vibration type, to grasp the relationship between the structure dynamic performance and the structural parameters; using ANSYS subspace identification method of shell theory of dynamic data, comparative analysis of reticulated shell structure theory and experimental data that based on ambient excitation modal analysis of the feasibility.Next to a Trestle bridge project as the background, based on ambient excitation of Trestle experimental modal analysis to obtain the modal parameters of the structure, and to test frequency and ANSYS analysis of frequency difference is taken as the objective function, the thickness of bridge deck is taken as the optimization parameters. Through the modal confidence criterion(MAC) index, contrast Trestle initial finite element and the modified finite element, recognition two stage even Gallery quality difference and concrete plate thick, and actual results are in good agreement.