Abstract
ABSTRACTThe distribution of fixed steel offshore platforms around the world reveals a global fleet that has exceeded or is approaching the end of the design life of the facility. In many operating areas, there is an attraction to continue using these ageing facilities due to continued production or as an adjoining structure to facilitate a new field development or expansion. To justify continued life extension of the fixed platform, various integrity assessment techniques are often used. One of the major techniques used is based on the phenomenon of local joint flexibility (LJF).While the phenomenon of LJF has been well known in the offshore industry since the early 1980s, there has been little experimental data available. In 1983, Amoco conducted an experimental study primarily to determine stress concentration factors associated with gapped K-type steel tubular joints. The LJFs calculated were based on the effects of in-plane bending, out-of-plane bending and axial compression and tension. The derivations of the existing LJF equations have evolved in many ways including use of finite element (FE) methods to predict the joint behavior. There has been no benchmarking exercise to large-scale experimental data.This paper provides an improvement on existing LJF equations by benchmarking the Amoco K-joints test results to a FE model and through a detailed parametric study. Improved formulations are provided for local joint flexibilities for gapped uni-planar K-type tubular steel joints.
Highlights
Kraincanic PhDThe distribution of fixed steel offshore platforms around the world reveals a global fleet that has exceeded or is approaching the end of the design life of the facility
The vintage of fixed offshore steel structures globally range from those installed in the 1950s to those designed to the latest code of practice [2,16]
The 72 geometric ranges in Table 8, will be used to develop ABAQUS structural models to determine LJF for the Balanced Axial, In-plane Bending (IPB) and OPB conditions using the methodology outlined in Figures 7 and 12
Summary
The distribution of fixed steel offshore platforms around the world reveals a global fleet that has exceeded or is approaching the end of the design life of the facility. He has developed particular skills in the area of life-cycle integrity management for energy related His experience includes conceptual field development studies, detailed design and analyses of both onshore and offshore structures including fatigue, seismic, vessel impact, decommissioning and ultimate strength considerations in a variety of operating regions including the Gulf of Mexico, North Sea, Latin America, Asia and the Far East. ABAQUS Suite of Finite Element Analysis Software American Oil Corporation American Petroleum Institute Atkins Structural Analysis System Billington Osbourne Moss Engineering Limited British Petroleum Det Norske Veritas Finite element methods Gulf of Mexico Health, Safety and Environment In-Plane Bending International Standards Organization Joint Industry Project Local Joint Flexibility London South Bank University MSL Engineering Corporation Oil and Gas Producer Out -of- Plane Bending Offshore Technological Conference (Houston) Risk Based Inspection Remaining Life Assessment Recommended Practice Underwater Engineering Group (UK) Ultimate Strength Finite Element Software Wimpey Laboratories Limited. Chord diameter Brace diameter Chord radius Axial displacement of the brace Displacement attributable to joint flexibility Young’s Modulus of Elasticity Axial force Flexibility matrix terms Chord Thickness Brace thickness Angle between brace and x-z plane (degrees) Angle between the brace and the x- axis Joint stiffness coefficient Chord length Bending moment Longitudinal gap length Transverse gap length Cross sectional area of the brace Brace to chord wall thickness ratio Brace to chord diameter ratio Chord length to chord radius ratio Radius to wall thickness ratio of the chord Gap parameter for K joint
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