Effect of Joint Flexibility on Overall Behavior of Jacket Type Offshore Platforms

Abstract

Problem Statement: Nonlinear behavior of offshore structure is attracting tremendous amount of attention in recent years. Response of these structures is strictly dependent upon behavior of their joints. Because of the lack of information about this part of a structure, most of the recent analysis and designs do not contain appropriate material in the case of joints. In most cases, joints are assumed to be fully clamped and their deformability is not accounted for in assessment of Jacket Type Offshore Platforms (JTOP) whereas, in reality there is always deformation in joints particularly when members undergo beyond elastic region. Approach: In this study, finite element modeling of tubular connections is carried out in order to assess their nonlinear behavior. As a result in a separate study, two FE models of a platform are made and effect of joint flexibility on these models is investigated analytically. Nonlinear static and dynamic analyses are performed considering joint deformation and compared to platform with clamped connections. Furthermore, some important parametric studies are carried out such as effect of joint flexibility on natural frequency of vibration of the structure and the process of plastic hinge formation in platform. Results: Results prove considerable effect of local joint deformation on nonlinear static and dynamic behavior of offshore structures. Conclusions/Recommendations: Taking into account the calculated results in this paper, it is highly recommended to consider the effect of joints in the design and analysis of offshore structures based on the importance of the project.