Cyclic Stiffness Degradation in Nonlinear Jackup Dynamics

Abstract

SNAME (2002) gives equations to describe degradation of foundation stiffness for jackup spudcans, depending on the size of a load cycle within a yield envelope. Using these and other proposals, this paper develops a simplified dynamic analysis of jackup cyclic response. Under static conditions, a lower-bound collapse load for a pinned foundation can be larger than for an encastré assumption. Under dynamic conditions, important nonlinearity because of stiffness degradation is confirmed. Chaotic dynamic responses may be possible.