Strength Performance of an Eccentric Jacket Substructure

Abstract

An eccentric jacket substructure is comprised of circular hollow section tubular joints with complete overlap of braces. The joint is formed with the lap brace overlapping the diagonal through the brace joining the chord face. In this study, the jacket substructure is subjected to a static vertical load due to self-weight and facilities, and four horizontal loads to simulate the environmental loads applied at four different horizontal angles. The maximum stresses at each level of the eccentric jacket are found lower than that of the traditional jacket. For the eccentric jacket substructure, the high stress critical area is mostly located at the short segment of the diagonal through brace joining the chord face. From the parametric study, the ultimate strength of the joint with the complete overlap of braces of the eccentric jacket reduces with increasing the gap size-to-through brace diameter ratio, ξ. With the short segment of the through-brace joining the chord face, the high-stress area is transferred from the joint intersection of the chord and the braces to the lap brace and the diagonal through-brace. It could; therefore, be concluded, based on the strength performance, that the eccentric jacket performed better with maximum stresses and high-stress critical areas.