Steel and titanum risers

Dynamic analysis

MARINTEK has been involved in major offshore field development projects in North Sea with their technical services for dynamic analysis of metal risers.  The work included:

• Conceptual studies
• Pre-engineering work
• Engineering work
• Third party verification work

In the past few years, advanced analysis procedures and methodologies have been developed to perform comprehensive nonlinear dynamic response of risers to assess the extreme load effects and fatigue response. These procedures are based on performing long (3 to 6 hour long) irregular wave dynamic response analysis. The nonlinear global response analysis takes into account complicated effects such as:

• Diffraction effects
• Nonlinear soil-riser interaction
• Coupling between risers and mooring lines
• Slow-drift motions combined with wave induced motions

Highly qualified technical personnel with sound project experience work as team a to solve individual design problems.

Fatigue Design Criteria

Titanium is an ideal material for compliant risers, due to large strength/weight ratio, flexibility and corrosion resistance.  Compliant titanium risers are a novel concept, and MARINTEK has been involved in the development of design guidance.  Research has been focused on fatigue performance of titanium welds, and fracture mechanics modelling of fatigue.  On the basis of a large test programme with participation from a number of suppliers of titanium, fatigue design criteria have been established and validated.

Contact persons: Oddvar Eide, MARINTEK / Stig Berge,NTNU