SIMILARITY METHOD FOR MODELING HYDROELASTIC OFFSHORE PLATFORMS

Similarity methods provide a very powerful technique for modelling off shore platforms. Such methods are preferable for situations where the wave-structure interaction process is complex, and its modelling canno t be expressed by rigorous mathematical formulations. In modelling the interaction between waves and an offshore platform, the dynamic prope rties of the wave and structure must be considered together to determi ne the similitude parameters. The paper gives details of such an inves tigation using a frequency response function approach. Three different models, which are termed general, distorted and nondistorted Freudian models, are developed. From the general model, it was found that the velocity scales of the wave and structure could be treated differently . Internal and external force scales could also be different. It is ob served then that a restrictive modelling criterion is used when the ve locity scale of a structure is obtained from Freudian scale modelling. Furthermore, detailed scales for practical use are developed. The mod el parameters for an acrylic plastic tripod tower platform with length scales of 1/50 and 1/70 are given, and the accuracy involved among th e three models determined for these scales. The sensitivity of the res ults to slight variations in thickness and Young's modulus are also di scussed. Copyright (C) 1996 Elsevier Science Ltd