Overview
ISO/TR 19905-2:2012 is a Technical Report that provides a detailed commentary and worked example for the site-specific assessment of independent leg jack-up mobile offshore units. It supplements ISO 19905-1:2012 by giving background, supporting documentation, alternative calculation approaches and a detailed “go-by” sample calculation (Annex A). The report is informative and intended for use together with ISO 19905-1 for reliable site-specific assessment of jack-ups in the petroleum and natural gas industries.
Key topics and requirements
This TR expands on selected clauses of ISO 19905-1 and addresses practical technical topics including:
- Metocean data: guidance on waves, currents, wind and water depth considerations for site-specific inputs.
- Hydrodynamic modelling: commentary on detailed vs equivalent leg models, member length, shielding and solidification effects, and spudcan behaviour.
- Wave, current and wind actions: methods to estimate environmental loads and associated coefficients (drag, inertia).
- Dynamic response: guidance on calculating jack-up natural period, effective stiffness (K), hysteretic damping and vertical radiation damping.
- Drag–inertia methods: explanation and application examples including SIPM “drag-inertia method” (Annex B).
- Foundation and spudcan interaction: commentary on soil–structure interaction, limiting horizontal reactions and skirted spudcan considerations.
- Structural acceptance and strength: guidance on nominal bending strength, interaction equations and design/assessment checks.
- Worked example: Annex A provides a step-by-step sample calculation for users to follow (“go-by” calculation).
Applications
ISO/TR 19905-2:2012 is used to:
- Support site-specific assessment and verification of jack-up units for design, decommissioning or relocation decisions.
- Provide practical calculation methods for hydrodynamic load estimation and dynamic response analysis.
- Serve as a reference for producing technically consistent assessment reports required by operators, owners and regulators.
- Benchmark analytical models and compare alternative modelling approaches.
Who should use this standard
- Offshore structural and geotechnical engineers
- Hydrodynamic and ocean engineers
- Technical consultants and engineering contractors
- Asset owners/operators and project planners
- Classification societies and regulatory authorities
Related standards
- ISO 19905-1:2012 - Jack-ups (mandatory companion document)
- Other ISO 19900-series standards covering metocean, geotechnical, seismic and offshore structural requirements (ISO 19900–19906)
Keywords: ISO/TR 19905-2:2012, jack-ups, site-specific assessment, mobile offshore units, metocean, hydrodynamic model, spudcan, drag-inertia, sample calculation.