Nonlinear Collapse of Offshore Jacket Structures

by Helen M. Bolt,
Colin J. Billington, (M.ASCE),
J. Keith Ward,

Document Type: Proceeding Paper

Part of: Structures Congress XII


The Joint Industry Tubular Frames Project was established with ten oil industry sponsors to investigate the reserve and residual strength of frames typical of offshore structures. To date ten large scale frame tests have been undertaken on what are thought to be the largest specimens loaded to collapse in a controlled manner. Both member and tubular joint failures have been exhibited and the mechanisms of load redistribution at progressive collapse have been examined. In parallel with the experimental programme, software has been developed and calibrated against the test results. An adaptive method has been used so that the structural model subdivides only introducing plasticity and mesh refinement when and where it is required. This leads to the efficient solution of complex nonlinear problems without placing reliance on the user to predict where plasticity will occur. The software is now being applied to the collapse analysis of jacket structures for requalification. Data from the first phase of the Frames Project were released from confidentiality in 1993, having first been used by other organisations to validate nonlinear software in a series of 'blind' benchmarking exercises commissioned by the UK Health and Safety Executive (HSE). This paper presents the findings and lessons learned through the Frames Project. Comprehensive background can be found in a major review on the reserve strength of structures recently completed by Billington Osborne-Moss Engineering Limited for the HSE.

Subject Headings: Offshore structures | Structural failures | Frames | Structural strength | Structural analysis | Failure loads | Failure analysis | Computer software

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