Structural Health Monitoring for Top-tensioned Riser with Response Data of Damaged Model

Risers are very important component of deep sea-bed mining. Unfortunately, risers have high risks of damage because they are exposed to harsh environmental conditions such as a current, pressure, high tension and vortex induced vibration. Therefore, it is very significant to retain riser's performance and to detect damage before the riser failure is occurred. A main objective of this paper is to propose a structural health monitoring technique to detect damage of a toptensioned riser. In this paper, the top-tensioned finite element (FE) model is considered as an analytical model of the riser, and a vibrationbased damage detection method with responses from damaged model is proposed. The present method consists of a FE model updating and damage index method. In order to accomplish the goal of this study, first, a sensitivity-based FE model updating method using the natural frequencies and the zero frequencies is introduced. Second, modal parameters of the top-tensioned riser are estimated by eigenvalue analysis. Finally, the locations and severities of the damages are estimated from the damage index method. Five numerical examples are considered to verify the performance of the proposed method.