The Impact of Wind and Waves on Offshore Jack-Up Systems

The unique demands of jack-up installation vessels

Installing offshore wind farms brings specific technical challenges. To position 200-meter-high turbines at sea, highly specialized jack-up installation vessels are required. At DEKC Maritime, we play a key role in the engineering behind these vessels and their structural adaptations. Unlike conventional ships, jack-up vessels are designed to transfer their entire weight onto just a few support points – typically four, though sometimes three or six. These vessels lower long steel legs to the seabed and elevate their hull out of the water, creating a stable working platform for heavy offshore cranes.

Balancing massive loads under harsh conditions

This principle, comparable to a land-based crane, requires a completely different structural approach. Traditional vessels distribute their mass via hydrostatic pressure; jack-ups concentrate loads onto legs that must remain absolutely secure, even under extreme environmental conditions.

Designing such vessels is an intricate process that goes far beyond standard naval architecture. Jack-ups integrate powerful cranes, additional thrusters, and a complex jacking mechanism that all must function in unison. With the growing size of offshore wind turbines, these vessels have become essential. There simply is no alternative for installing the latest generation of turbines in the North Sea.

Safety remains a top priority in jack-up design. Structural failure is not an option. The loads involved can reach thousands of tonnes, and the vessel often operates elevated above the waves for extended periods. During operations, environmental conditions can change – wind and currents apply steady forces, but it is the waves that pose the biggest threat. While the vessel is jacked up, the legs still respond to dynamic forces from the sea.

Large structures like these move slowly, much like tall buildings. If wave frequencies match the natural frequency of the vessel, resonance occurs. The resulting oscillations can amplify significantly, putting dangerous stress on the legs. Even relatively small forces, if applied at the wrong frequency, can lead to failure. This phenomenon is well-documented in structural engineering, from the collapse of the Tacoma Narrows Bridge to issues once faced by the Erasmus Bridge in Rotterdam, which had to be reinforced to prevent vibration-induced damage.

Resonance: the silent threat at sea

Predicting and managing resonance is a key part of our expertise. Using advanced simulation tools, we model the complete structure of a vessel in great detail, down to each bulkhead and piece of equipment. But tools alone are not enough. It’s the engineering insight behind the models that makes the difference. Over the past two decades, DEKC Maritime has developed unique capabilities in this area, making us one of the few offices in the Benelux with this level of in-house knowledge.

From earthquake science to offshore innovation

That expertise has even led to international recognition. When we observed that the dynamic behavior of jack-up vessels closely resembled the vibration profiles of civil structures exposed to earthquakes, we adapted seismic calculation methods to offshore applications. After presenting this approach to DNV in Oslo, the method received formal approval. This insight, that even small changes in leg stiffness can shift resonance periods, has helped raise the standard for jack-up safety and set a new benchmark in offshore engineering.

Innovation is our DNA

Innovation like this is part of our DNA. Throughout the years, we’ve consistently introduced new, technically sound solutions that meet, and often exceed, classification and regulatory demands. This drive to challenge norms and rethink marine engineering solutions is what defines us as a team.

Working at DEKC Maritime is not only technically challenging, it’s also creative and varied. Many of our engineers come from backgrounds in aerospace or mechanical engineering rather than traditional shipbuilding. We don’t just design new vessels, which are then built by external shipyards, we also develop custom tools and retrofit solutions for existing ships to meet new operational needs. Every project must comply with evolving regulatory requirements, which keeps our work dynamic and pushes us to think beyond conventional boundaries. At DEKC, complex challenges are not seen as problems, but as opportunities for innovation.