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Structural Engineering and Mechanics
  Volume 29, Number 3, June20 2008, pages 311-325

A model experiment of damage detection for offshore jacket platforms based on partial measurement
Shi Xiang, Li Hua-jun, Yang Yong-chun and Gong Chen

    Noting that damage occurrence of offshore jacket platforms is concentrated in two structural regions that are in the vicinity of still water surface and close to the seabed, a damage detection method
by using only partial measurement of vibration in a suspect region was presented in this paper, which can not only locate damaged members but also evaluate damage severities. Then employing an experiment
platform model under white-noise ground excitation by shaking table and using modal parameters of the first three modes identified by a scalar-type ARMA method on undamaged and damaged structures, the feasibility of the damage detection method was discussed. Modal parameters from eigenvalue analysis on the structural FEM model were also used to help the discussions. It is demonstrated that the damage detection algorithm is feasible on damage location and severity evaluation for broken slanted braces and it is robust against the errors of baseline FEM model to real structure when the principal errors is formed
by difference of modal frequencies. It is also found that Z-value changes of modal shapes also play a role in the precise detection of damage.
Key Words
    damage detection; offshore jacket platform; model experiment; partial measurement; shaking table.
Shi Xiang, Li Hua-jun, Yang Yong-chun and Gong Chen:
Engineering College, Ocean University of China, Qingdao, 266100, China

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