A numerical analysis of fixed offshore structure subjected to environmental loading in Malaysian water

Abstract

This research focused on the response of the jacket structure to environmental loading. The jacket was modelled as a space frame using ANSYS finite element package. Meanwhile, the estimation of extreme value of environmental parameters based on data on Malaysia waters was carried out using MINITAB. Response of the structure under environmental loading was performed using static analysis. Interaction ratios of the members are computed based on API RP2A–WSD (1993) using MATLAB. The sensitivity of the jacket structure to variation in design parameters was investigated. From global stress analysis, one of the structure’s member on a complex multiplanar leg joint, appeared to have a high utilisation of stress when assessed using API RP2A–WSD (1993). Therefore, a nonlinear finite element analysis of the multiplanar joint has been carried out to determine both the absolute load capacity of the joint, the effect of the out–of–plane loads and braces and relate these back to the strength of the critical brace acting as a Y joint. This study presents the analytical methods and results together with a calibration of the analysis against test data for Y joints. A systematic study of stresses in tubular Y joints has also been conducted using finite element analysis which covers axial loading, in–plane bending and out–of–plane bending. For each mode of loading, and for both chord and brace sides of the intersection, stress concentration factors and its distributions are calculated for selected locations. The validity of this approach is demonstrated by comparing the finite element results with the predictions of other previously published parametric equations