Study: Measuring the impact of extreme waves on offshore structures

Strong storms can trigger steep, breaking waves that slam into platforms and wind turbines with tremendous force. Scientists at NTNU and SINTEF are studying the behaviour of offshore structures subjected to these kinds of waves. Their goal is to increase safety at sea.

Study: Measuring the impact of extreme waves on offshore structures
Photo: Sleipner A platform/Equinor

The force of waves slamming into offshore rigs, wind turbine pillars, ships or other offshore structures can do an enormous amount of damage.

One of the fundamental – and unresolved – problems with designing these kinds of large structures is being able to predict exactly how they will react to extreme stresses. What exactly is the load from the force of powerful waves slamming into structures?

Solving these challenges will be a major step towards safer and more cost-effective marine operations.

Rene Kaufmann says:

“It’s crucial to understand the mutual interaction between the impacting wave and the response of the structure.”

Kaufmann is a postdoctoral fellow at the NTNU SIMLab (Structural Impact Laboratory) and one of the researchers in the SLADE KPN project. This is a Knowledge-building Project for Industry (KPN) funded by the Research Council of Norway, in which researchers from SINTEF Ocean and NTNU are collaborating on basic research. The overall goal is to increase the safety at sea.

Photo: Vegard Aune, SIMLab

It’s important to expand what’s known about these challenges, but that will require systematic experimental studies of wave-impact scenarios. The project will do exactly that, which should allow researchers to figure out how a structure’s behaviour interacts with the loads that are applied to it.

The researchers are developing experimental methods to measure this interaction. Better calculation methods can help the industry when new offshore structures are designed.

Kaufmann’s focus is measuring the impact of local surface deformations from massive loads.

One important aspect of Kaufmann’s research is to make sure the measuring equipment itself doesn’t affect the structure’s properties. Researchers at SIMLab have used their experience with camera-based techniques to measure the structural response to loads from impacts and explosions.

Kaufmann, along with fellow researchers Bjørn Christian Abrahamsen from SINTEF Ocean Transport & Energy and project engineers Trond Auestad (SIMLab) and Jens Åge Havmo (SINTEF Ocean), recently spent several days in the Ocean Basin Laboratory at Tyholt in Trondheim, where they conducted wave slamming tests on small-scale models.

The researchers tested the measurement technique they had worked out, which involves measuring the load as the wave strikes the structure.

Today, this is measured with point meters that rely on wires. The SLADE team has been exploring the use of lasers and camera techniques that not only provide measurements at a given point, but can potentially determine in time and space how the entire incoming wave field evolves as it approaches the structure.

This development is leading to another goal for SLADE, that of bridging the gap between physical tests and reliable computer simulations.

The researchers recreated breaking waves in the basin, causing them to slam into a flat steel plate. The plate was integrated into a steel pillar representing a scaled-down steel structure at sea.

SLADE KPN was launched in 2019, but the partners involved have a long shared history of collaboration.