Analytical and Numerical Investigation of a Steel Module with a Postbuckling Transition Mechanism for Dynamic Dissipation

Abstract

Sudden extreme loads acting on a marine structure can seriously damage components; thus, a structural module is beneficial for simultaneously load bearing and energy dissipating. However, the low damping characteristic of metal members allows a lasting dynamic response. In this paper, a specially designed metal module is proposed. In this module, the postbuckling transition of the inner eccentric columns in the elastic state creates a hysteresis relation with an initial stiffness that is close to that of the metal material under a tension-compression load. The hysteretic characteristics of this module are simulated via finite element modeling (FEM). Theoretical models are deduced to determine the critical buckling and postbuckling transition; this work results in a piecewise equation that approximately describes the system dynamics. Using an averaging method, the constitutive relation between the structural slenderness parameter and dissipation performance is delineated by obtaining analytical expressions for the time-domain variation in the response amplitude. Analyses of different geometric parameters illustrate the damping and stiffness design of the nonlinear module. The hysteresis module is integrated as a bracing member and embedded in a representative jacket platform. In the simulation, a three-dimensional FEM and a user-defined material (UMAT) subroutine are combined in ABAQUS such that the hysteretic bracing member mitigates the wave impact response of the structure within the elastic range. The simulation results demonstrate the potential of the hysteretic module with a postbuckling transition mechanism to ensure high stiffness and to enhance damping in marine structures.