Analytical solution on the surge motion of tension-leg twin platform structural systems

In this study the wave induced surge motion of a twin platform of a pretens ion leg structural system is investigated. A set of equations along with bo undary conditions are derived, and solutions are obtained analytically. The tension-legged twin platform structural system might better represent a pl atform system in the practical application in either idealized two-dimensio nal analysis or actual three-dimensional practice than a single platform sy stem. In the analysis the coupling problem of a two-dimensional tension leg twin platform interacting with a monochromatic linear wave train in an inv iscid and incompressible fluid is considered. The problem is considered as a combination of the scattering and radiation. These two boundary-value pro blems are first solved independently and then combined together to resolve for all unknowns. The analysis is focused on the wave induced surge motion of the twin platform and the reflection coefficient. Other than the wave-re lated parameters, the dimensional effect of the twin platform structure is examined and presented in numerical examples. From the analytical results, it is found that the behavior of the tension-leg twin platform is significa ntly influenced by dimensional factors of the platform system such as the d imension of each single platform and the spacing between two platforms. It is also realized that to simplify the analysis of a twin platform system in to a single platform, it tends to underestimate the wave-induced response a nd then reduces the safety of the platform system. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.