Structural calculations: ensuring safe deployment and operation of wind turbine installation jack-up vessels

Structural calculations: ensuring safe deployment and operation of wind turbine installation jack-up vessels

Used for offshore operations, jack-up vessels are floating units with deployable legs attached to the hull. The platform can be raised above the water level, ensuring stability for operations such as drilling, foundation piling and wind turbine lifting and installation. Jack-ups are self-propelled or tugged by another vessel. They are designed for shallow water operations.

Jack-ups take on different forms and functions according to how they will be used. For example, jack-ups for wind turbine installation (WTIV) need to be jacked up very frequently, impacting their design specifications. However, mobile offshore drilling units (MODU) will be jacked up less frequently due to the nature of drilling operations.

Evolving market needs

As the offshore wind market develops, jack-up specifications are evolving to meet new operational needs. Wind turbine size in the European market has grown significantly in recent years, with an average turbine size of 12 MW expected by 2025. Jack-ups therefore need sufficient capacity to transport this large machinery. Some older vessels are no longer able to lift new wind turbines and are being repurposed for other operations, such as service and maintenance operations. This brings about a need for new build jack-ups designed to handle the largest wind turbines on the market.

Jack-ups for fixed offshore wind farms have certain specifications – crane lifting capacity and maximum water depth deployment – which need to be reflected in the design. Designers must examine the hull to ensure it is strong enough to handle the required load. Stakeholders are also increasingly concerned by the productivity of the vessel and its ability to transport multiple turbines to save on journeys. Since jack-up vessels will be in operation much more frequently for wind turbine installations, owners need to guarantee their reliability.

The importance of structural calculations

In light of these challenges, it is important for owners to be able to understand and predict the jack-up’s behavior, particularly the leg-hull interface. This is all the more important for vessels operating in challenging conditions, with considerations such as storm survival, efficient leg pre-driving, soil variations, barges moored alongside operations and negative airgap operation.

To foresee future issues, structural calculations are an essential part of the design phase. A digital twin can enable the combination of structural numerical models and on-board monitoring data.

Structural calculations

Complex studies need to be carried out to gain an in-depth understanding of the jack-up’s structural behavior. This ensures the safe deployment and operation of WTIVs. Structural calculations cover:

  • Structural integrity and strength analysis, using a Finite Element Analysis tool, including:
  1. Full ship strength analysis to ensure structural integrity of the hull and legs for design and extreme load cases
  2. Detailed strength assessment in high-stress areas to account for the impact of heavy equipment and maximize payload capacity
  • Fatigue analysis to predict and prevent structural fatigue and extend the jack-up’s operational life
  • Complex non-linear analysis to evaluate wave loads and the leg-hull interface

In addition to structural calculations, there are a number of requirements to consider during the design phase. The vessel design must be adapted for its intended use, taking size into account. The jack-up also needs to be light—every lightship ton added to the hull is a payload ton that cannot be lifted, reducing cost-efficiency. Risk analysis is equally a key aspect of the design phase. The vessel should be positioned taking into account seismic risk and maximum seismic load, for example. Another important step is the pre-driving of the legs, where pairs of legs carry the hull weight in turn to achieve the foundation pre-load. This guarantees the vessel’s soil foundation stability before jacking up cargo.

An expert partner for jack-up deployment

BV Solutions M&O supports jack-up owners throughout the vessel’s lifespan, from design through operations and upgrades. Our expert teams offer technical solutions and structural calculations, providing valuable assistance during the design and operational phase. We help owners understand and predict the jack-up’s behavior. Our services are tailored to the specificities of your jack-up, whether a new build or a retrofit. Since a jack-up may undergo several different missions throughout its operation, BV Solutions M&O provides support later in life to overcome new challenges and ensure safe redeployment.

New wind farm installation needs are seeing jack-ups with lifting capacities of over 3,000 metric tons, able to carry blades over 110 meters long. BV Solutions M&O is accompanying this new generation of jack-up vessels, as we draw on all our expertise in hydrodynamic studies as well as structural computation. Working on these pioneering vessels inevitably presents new challenges. Our BV Solutions M&O teams have adapted our technical support, raising new considerations and developing existing studies to be even more rigorous.

The BV Solutions M&O difference

BV Solutions M&O provides personalized support to suit clients’ needs. Our extensive experience enables us to offer complex calculations and meet demanding specifications, working in close collaboration with our clients. As part of a renowned global group, we have an in-depth understanding of engineering, class, operations, technical solutions and all other aspects important to jack-up owners. Our structural calculations provide owners with peace of mind when deploying their jack-up vessels.

Aymeric David

Head of Structural Section

BV Solutions M&O

We are proud to have assisted with the deployment of wind turbine installation jack-up vessels around the world. Our teams are at the cutting edge of jack-up innovations to provide expert technical consulting and structural calculation services.