Vol 7, No 6 (2016) > Civil Engineering >

The Effect of Symmetrical and Asymmetrical Configuration Shapes on Buckling and Fatigue Strength Analysis of Fixed Offshore Platforms

Muhammad Zubair Muis Alie

 

Abstract: The fixed jacket is
still the most common offshore structure used for drilling and oil production.
The structure consists of tubular members interconnected to form a
three-dimensional space frame, which can be categorized into a column
structure. The structure usually has four to eight legs that are battered to
achieve stability against axial compressive loads and toppling due to wave
loads. The configuration of a typical member on the jacket structure has
significant influence on buckling and fatigue strength. Horizontal and diagonal
braces play an important role in resisting the axial compression and wave load
on the global structure. This
paper discusses the effect of symmetrical and asymmetrical configuration shapes
in buckling and fatigue strength analysis on two types of fixed jacket offshore
platforms. The axial compressive and lateral (wave) loads were considered and
applied to both structures. The material and dimensions of the two structures
were assumed to be constant and homogenous. Crack extension and corrosion were
not considered. To assess the buckling and fatigue strength of these
structures, due to the symmetrical and asymmetrical configuration shape, the
finite element method (FEM) was adopted. Buckling analysis was performed on
these structures by taking two-dimensional planes into consideration to obtain
the critical buckling load for the local plane; fatigue life analysis was then
calculated to produce the fatigue life of those structures. The result obtained
by FEM was compared with the analytical solution for the critical buckling
load. The stress-strain curve was also applied to show the difference between
symmetrical and asymmetrical shapes. For fatigue life analysis, the procedure
of the response amplitude operator was applied.
Keywords: Buckling analysis; Fatigue analysis; Finite element method; Fixed offshore platform; Symmetrical and asymmetrical shape

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