Fixed Structures

Fixed structures come in a range of sized and configurations – depending on their purpose.   The desing of many foundations is driven not only by the environment in which it must work, but also by the requirement for installation be it lifted, lauched or float-over.  Longitudes experience of fixed structure design considers the through life requirements whether the structure be an offshore jacket and topsides, a jetty structure or a wind farm foundation.

• • Concept, PRE-FEED and Detailed Jacket and Topside Design
  • Conductor Supported Platforms
  • Pile and Conductor Design and Analysis
  • Gravity Base Structures (GBS)
  • Oil and Gas and Renewables Experience
  • Design for both benign and harsh environments.
  • Installation Design and Analysis
  • Geotechnical Site Characterisation, Design and Analysis
  • Metocean Analysis to set the design basis
  • Commercial assessment of the asset from build to operation.
  • Design for Installation (Launch, Floatover, Heavy Lift)

Longitude’s experience with marine and off-shore fixed structures addresses the entire life cycle of an asset, from initial concept through to decommissioning.

All marine structures have a finite life, but that life may be extended through careful maintained or upgrades.   Longitude has been providing clients with support for both floating and fixed strcutures in service and offer the following services:-

• Modelling of existing fixed structures
• Strength and Fatigue Analysis based on inspected and gauged structures
• Historic Metocean analysis to allow a comparison of design environment with observed environment since installation
• Re-calibration of fatigue life based on actual historic environment
• Interpretation of Structural Monitoring
• Liaison with certifying authorities
• Steel renewal plans
• Mitigations for cracks or corrosion
• Fitness For Service Assessment

Longitude has carried out the detailed design of all manner of marine and offshore installation engineering from jackets and topsides through to FPSO mooring and risers. In doing so, Longitude is experienced with the wide range of marine fleet from tugs and barges to DP construction vessels and module carriers. To execute these installation engineering projects, our specialist engineers provide a range of services, such as:

• • Dynamic lift analysis in air and through the splash zone
  • Motions, mooring and stability analysis
  • Grillage and seafastening design
  • Structural design for installation
  • Mooring line pull in assessment
  • Floatover Engineering
  • On-bottom stability
  • Risk Assessment
  • Preparation of Operational Procedures and Method Statement
  • Dropped Object and Impact Analysis

These same skills are used by Longitude for decommissioning engineering whether small piece methods or whole structure removal is required. In addition to developing engineering for marine operations, Longitude can provide method statements, risk assessments and procedures for all operations. This ensures consistency between the engineering and procedures and ensures the project safety throughout the operation. Longitude’s project teams can attend or facilitate HAZID’s or SIMOPS sessions for each operation

Longitude has taken his our knowledge of fixed structure installation engineering to develop safe, effective engineering systems for decommissioning. These range from small platforms with 1,000 to 2,000 tonnes of topside weight, to systems for removal of large platforms up to approximately 25,000 tonnes. As part of the oil platform decommissioning process, Longitude assesses what is needed to safely lift the topsides and if necessary to design temporary strengthening of the topsides.

Subsea structures have similar design requirements to fixed jacket or topside structures.

Our structural engineers have provided engineering design and analysis for offshore jackets and topsides as well as structural analysis of trenchers, PLEMs and other subsea structures. In addition, Longitude has provided impact loading and dropped object analysis for subsea structures and pipelines.

Fixed structures and subsea structures,  are always depending upon the seabed soils and foundations for their integrity.  Our structural and geotechnical engineers work together to design any strcutture that interfaces with the seabed, be it a Gavity BAse Strcutre, Conductors, Piles or Suction pile foundations.