A Review of In-Place Design Approaches for Spar Hulls

This paper reviews the current practice for the in-place design of Spar hulls. Both the commonly-used approach and the state-of-the-art procedure for the maximum strength and fatigue conditions will be presented. Key assumptions for various design approaches will be discussed along with advantages and disadvantages of each approach. The review will focus on how each approach generates hydrodynamic loadings, performs global motions analysis, and maps design loads from motion analyses to structural finite-element model. Important aspects relating to Spar design will be addressed. In particular, effect of vortex induced hull motions (VIM) will be discussed, and an approach for including the VIM effect in the design of moorings and risers will also be described. Impact on the maximum strength and fatigue capacity of critical structural components due to the assumptions employed in the commonly-used design approach will be evaluated and quantified as compared to the results from the more rigorous state-of-the-art approach.