Structural Design

NIRAS is involved with design and engineering of steel foundations for large offshore wind farms including supports for wind turbine generators (WTG's). Design works includes hydrodynamic, structural and installation  design as well as cable protection, cable routing and cable dynamics analyses.

NIRAS provides support during all phases of the design of offshore wind turbine generator support structures, starting from site investigations, conceptual through to detailed design, detailed drawings, fabrication, transport, installation and in-service until decommissioning.

NIRAS provides the following services:

• Conceptual and detailed design services for secondary and primary steel

• MP detailed partly automated design program including the full geotechnical design

• Pile driving analysis

• Flange FEM analysis including detailed bolt modelling, pre-tensioning, driving, in-situ and fatigue utilization

• Corrosion protection active/passive systems

• Scour protection/analysis

• Detailed fabrication drawings, monopile, jacket structures, bucket foundations

• New solutions/innovative design

• Special engineering: structural, hydrodynamics, cable dynamics/tie-in, geotechnical analysis

• Example projects: Blyth Harbour, Scroby Sands, North Hoyle, Northwind, Rampion, Kriegers Flak, Vesterhav Nord/Syd, Dafeng, Changua, Xuven, Hai Long, and Dogger Bank

• Review and evaluation on ad hoc basis

The TP-less Scroby Sands design featured and external cage structure and a hanging internal airtight platform (ATP). This ATP was onshore installed in a damped suspension arrangement prior to the offshore pile driving operation. Recently, we have developed a internal ATP with a Client (patent pending), which saved lots of time during offshore installation of the windfarm foundations.

Offshore High Voltage Substations Support Structures

NIRAS carried out detailed design of a number of Offshore High Voltage Substations (OHVS), including monopile foundations (Northwind) and jacket structure foundations (Jieyang OHVS foundation shown bottom right picture) and jacket/concrete hybrid foundation (Anholt OHVS foundation shown on main picture and two top picture right).

NIRAS carried out installation engineering and site supervision of critical tasks for some projects.

NIRAS has supplied various structures and components to the offshore and subsea industry.

NIRAS has supplied various structures and components to the offshore and subsea industry. The supply is mainly generated by Client request. NIRAS will typically apply one or more fabrication contractors which will typically be local Esbjerg yards and we work in close cooperation with the subcontractors. Typically, NIRAS will be involved directly in FAT, functional and integration testing. Furthermore, we engage with third party for weld control, testing services, witnessing and documentation. Examples on the supplies are:

• Clawloks Bending Stiffener Latching Mechanism, LIC proprietary design (patent pending), approx. 25 sets (male + female units) supplied

• Sling Tensioners for jack-up platform strengthening

• Xmas tree support frames

• Cross over flange for Xmas tree in temporary condition

• Chemical injection system, prototype on-stream high-pressure injector developed, patented and tested

NIRAS has regularly been engaged to carry out testing services for offshore and onshore equipment. Work includes FAT testing of NIRAS supplied components, testing of cables to determin the structural properties, testing related to insurance and root cause investigations for structural failures and testing of malfunctioning transport equipment for onshore road transport of very heavy components.

NIRAS has a 12 m long horizontal testrig based in Esbjerg which allows us to carry out structural cable testing for wind farm offshore array and export cables. We also have possibilities for vertical suspension to determine cable dynamic behaviour. NIRAS has delivered testing sevices for a number of specific jobs relating to offshore/subsea cables in the North Sea. Some of the tasks have been:

• Cable mechanical static properties and dynamic behaviour

• Root cause identification for failed cables during pulling operations, cable twist

• Testing of cable protection systems (CPS) including repair engineering

• Cable clamp capacity

• Clawloks connector, steel-steel connection system, CPS connection to J-tube/MP hole

• Testing and design of external and internal J-tube systems

• Integration testing including testing of Airtight platform (ATP) solutions

• Subsea epoxy grouting tests

• Scour tests

NIRAS has a wide range of research and development in mechanics ranging from various connectors to clawloks.

NIRAS' Research & Development of Mechanical Design