Model Study of Effects of Damage on the Vibration Properties of Steel Offshore Platforms

摘要

The selected vibration properties of an offshore platform model were studied considering both damaged and undamaged conditions. The platform model was a 1/50th scale, three dimensional tower possessing the key features of a typical, eight legged, k-braced steel offshore platform. Changes in the vibration frequencies and mode shapes of fixed offshore platforms can be used to detect damage. In this study, for the first time, quantitative information on mode shapes was utilized leading to improved damage detection capabilities. The scaling considerations, the model and the experimental method are described. The experimental results are complemented with analytical results and show excellent correlation. In general, emphasis is placed on the vibration frequencies and deck modal displacements of the first two translational modes and the first torsional mode. The effects of a variation in deck mass are assessed both experimentally and analytically. Also, the effects of shifts in the position of the deck center of mass are assessed analytically.