Nonlinear Dynamic Analysis of 2-D Jacket Structure Considering Joint Nonlinearity

Abstract Jacket structures are recognized for their fixed-base design and inherent structural stiffness among the most critical offshore engineering structures. This rigidity, stemming from their solid connection to the foundation, results in a slightly shorter natural time period than their floating structures. Comprising a framework of interconnected tubular members with rigid connections, jacket structures offer durability and stability in the challenging offshore environment. However, the operational performance of these jacket structures is significantly influenced by dynamic forces arising from the random ocean environment. The interaction between the random ocean dynamics and the structural integrity of jacket structures can lead to joint rotations and deformations, introducing nonlinearity into the system. The extent of joint nonlinearity is a critical factor that can intensely affect these offshore structures’ dynamic responses. This comprehensive study extends its focus to involve complete 2D jacket structures by using Finite Element Analysis (FEA) software ABAQUS to model joint behaviour and understand the details of nonlinear dynamic behaviour. The joint modeling approach not only considers the influence of varying angles between members but also accounts for joint level buckling under varying external loading conditions. In the presence of joint buckling, the nonlinear behaviour of the jacket structure changes significantly. This becomes more significant because it may cause significant fatigue damage to the structural joints. The study is focused on understanding the joint buckling and its nature under random ocean waves for a 2D jacket structure. Further, the effect of buckling on the nature of response is studied. This research enhances our understanding of the interaction between structural nonlinear elements (under joint buckling) and dynamic forces, ultimately offering essential information for offshore engineering design, assessment, and safety.