OCAS’s unique fatigue testing technique chosen to look into the viability of single-sided welds for offshore structures

Following the successful outcome of the "Improved Fatigue Life of Welded Jacket Connections" JaCo project, OCAS is once more the Carbon Trust’s Offshore Wind Accelerator preferred partner in their new project "Fatigue Assessment of Single-Sided Welds in Tubular Joints for Offshore Wind Foundations. This ASSISI research project will look at the viability of single-sided welds in tubular joints for offshore structures.

New research, investigating single-sided welding for offshore wind foundations, could cut the cost of wind turbine fabrication

If found to be successful, this new welding methodology could help ease bottlenecks as governments around the world seek to deliver on ambitious renewable energy targets, often stalled by construction times. The Fatigue Assessment of Single-Sided Welds in Tubular Joints for Offshore Wind Foundations (ASSISI) project is led by OCAS and delivered in collaboration with their Belgian research partner and foundation manufacturer Iemants (Smulders) as part of the Carbon Trust’s Offshore Wind Accelerator (OWA) programme.  The research project will look at the viability of single-sided welds in tubular joints for offshore structures and run until 2025.

If the fabrication method is found to be effective for offshore wind structures, it could replace the preferred double-sided welding method used across the industry. It could also cut fabrication and manufacturing times for future windfarm sites. The three-year project will conduct 15 fatigue tests across different types of large-scale structures, in addition to a number of small-scale fatigue tests to determine detectable flaw size. This will include numerical simulations and physical testing to replicate the impact on the weld over a structure’s 25-year lifespan.

Read the full press release here.

The OWA ASSISI project is funded by a partnership between EDF Renouvelables, Parkwind, Scottish Power Renewables, Shell, SSE Renewables, TotalEnergies and Vattenfall, and is being delivered by OCAS in collaboration with foundation manufacturer Iemants (Smulders). The project also received funding from the NextGenerationEU programme, made available through the Flemish Agency for Innovation and Enterprise (VLAIO).


OCAS’s proprietary testing method is based on an increased frequency of 20 Hz, significantly speeding up the delivery of results to within just 14 days for a full-scale jacket node.


“We are pleased to be part of this challenging project with the Carbon Trust OWA and a fine selection of offshore wind farm operators. We are looking forward to determining the fatigue performance of single-sided welds in their full scale, whereby we aim to increase productivity and reduce cost of offshore wind foundations further, on both monopile attachments and jacket foundations.”

Philippe Thibaux, Senior Structural Integrity Specialist, Applications and Solutions department, OCAS

“Through a better understanding and accelerated testing of a significant number of  single-sided welds, we hope single-sided welding can become industry standard, potentially speeding up and cutting the costs of fabrication for offshore wind foundations.”

Marc Vanderschueren, Senior Business Development Manager, OCAS

“It is exciting to see how our accelerated fatigue testing results are used to study the potential of offshore structures”

Jeroen Van Wittenberghe, Senior Team leader large scale testing, Applications & Solutions department, OCAS