局部計測に基づく海洋ジャケットプラットフォームの損傷検出

概要

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A new algorithm to detect damage in structures using partial measurement of vibration in a target detecting region is proposed based on the observation that damage occurrence of jacket-type offshore platforms is concentrated in two regions. The feasibility of the damage localization algorithm is tested by employing a numerical model of an offshore jacket platform of which pre- and post-damage modal parameters are available for few lower modes of vibration. First the validity of the new algorithm using changes in partial mode shapes is examined in comparison with the existing algorithm using global mode shapes by utilizing modal parameters from eigenvalue analysis. Next, regarding the simulated dynamic responses of the structure under white-noise ground excitation as ambient vibration measurement from which modal parameters are identified using an ARMA method, the proposed algorithm is applied to locate damages simulated in the structure. It is demonstrated that the damage detection algorithm in connection with the ARMA modal identification is feasible and robust against measurement noise as well as the identification error of baseline structure, and that no false prediction of damage location may occur when damages happened outside the detecting region.
2005-05-30