Numerical and Experimental Study of the Dynamic Characteristics of a Simplified Compliant Buoyant Tower

摘要

This paper presents numerical and experimental modelling of the dynamic characteristics of a simplified offshore compliant buoyant tower (CBT). The finite element analysis (FEA) package ANSYS 8.1 was employed to model the effects of seabed stiffness, topside mass and additional buoyancy, and these parameters were varied to investigate how each influence the natural period of the compliant buoyant tower in water. Accordingly, still water testing was conducted in order to validate the methods used in modelling submersed pipes and large buoyancy tanks in the finite element analysis software. Testing involved three different seabed or base circumstances: fully fixed, rotational spring and a universal joint. Each of the three base conditions allowed for the observation of either the rigid and/or the elastic body motions. The enclosed buoyancy chamber providing the buoyancy force was fabricated so that its position could be adjusted during the tests. The payload of the structure was also made changeable in both the still water tests and finite element modelling. The dynamic characteristics and responses obtained from the tests are reported and comparisons are made between the FEA and the model testing results.