Dynamic Analysis of Jacket Type Offshore Platforms Considering Connections Flexibility
Offshore steel jacket structures consist of tubular members and associated joints. For simplified computer analysis, connections between the elements are assumed to be rigid, which means that there would be no axial rotational or deflection at the end of the secondary member against the main member’s axis. Nevertheless, the tubular joints have remarkable amount of flexibility in the elastic–perfectly plastic region. In this study, two models of a 3D frame of a fixed steel platform SPD7 existing in the Persian Gulf are made. Nonlinear static and dynamic analyses with respect of joint flexibility are performed and compared to platform with rigid connections to investigate the effect of joint flexibility on natural frequency of the structure. The results show that the natural frequency of platform without flexibility has been increased even though the effect of increasing the ductility to the Platform’s frequency was predictable. Besides, by performing dynamic history analysis and investigating the exact effect of connection flexibility, the results show that the base shear values are reduced compared to the rigid model. It proved that local joint flexibility has considerable effect on nonlinear static and dynamic behavior of offshore structures.
Keywords- Tubular Joint, Jacket Type Offshore, Dynamic Analysis