Assessment of Welded Structural Joints in Subsea Module Frames

Abstract

In structural design, optimization is a keyword by means of selecting the best design within the boundary conditions provided by a given system. Structural engineering is a well-known discipline and there have been conducted experimental, analytical and numerical studies through decades. In this study, three different assessment tools have been used to consider two different design methods of structural frames. One based on open profiles in lower and upper horizontal part of the structure, and one based on closed profiles used extensively in the structure. Structural joints are an integral part of the structural frames, and the approach her is to extract and analyze two regular joints, T- and K-joint. The method used for the assessment of open or closed profiles is divided into three independent parts. There has been performed parametric calculations according to Eurocode 3, finite element analysis (FEM) with boundary conditions beyond the scope of the standard and an assessment of the manufacturing parameters influencing the two design systems. The parametric calculations have shown that for the T-joint exposed to axial compression and out of plane moment, the open section is showing the best resistance to failure. For the K-joint the method with closed section in lower and upper horizontal part of the structure is showing the greatest resistance to failure. The scope of Eurocode 3 is limited by simple load cases and real systems will often extend beyond these boundaries. In this sense, finite element analysis has been used to investigate structures beyond the code. From the finite element analysis, the strain/stress distribution overt the two K-joints adapted in the models show that the design with closed profiles resist failure modes more efficiently than configuration with open sections chords.