Awarded: Japan Society of Civil Engineers Technology Award (Group II) for 2026

Nippon Steel Engineering Co., Ltd. (President: Yukito Ishiwa, Head Office: Shinagawa-ku, Tokyo; hereinafter "the Company") announces that it, together with Hibiki Wind Energy Co., Ltd., J-POWER (Electric Power Development Co., Ltd.), Kyuden Mirai Energy Co., Ltd., and Goi Kajima Corporation, has been awarded the Technology Award by the Japan Society of Civil Engineers for its contributions to the Kitakyushu Hibiki-ko Offshore Wind Farm project (hereinafter "the Project").

The Project involves constructing Japan's largest bottom-fixed offshore wind farm, with a maximum output of 220 MW generated by 25 large wind turbines, each with a capacity of 9.6 MW. The turbine installation area features varying water depths of 8 to 30 meters and a heterogeneous seabed composed of soft sandy and cohesive soils, as well as bedrock. To accommodate these diverse water depths and geological conditions, the project adopted the "jacket-type" foundation.

In the design and fabrication process, the project team established a novel design methodology by combining two types of jacket foundations—4-pile and 8-pile configurations—and for the first time globally, concurrently employing three different pile installation methods. This approach enabled optimal foundation selection for heterogeneous seabeds containing bedrock. Despite complex site conditions, design innovations allowed the 25 turbine foundations to be consolidated into just eight types, significantly improving productivity in design and fabrication.

Furthermore, for evaluating pile bearing capacity in bedrock, the team established a rational assessment method by conducting pull-out load tests for each rock type and grade, considering the varying ultimate shaft friction resistance among different rock types such as sandstone, mudstone, and granite. In seismic design, to address Japan's unique earthquake conditions, a high-precision analytical method was developed using a "multi-mass-point blade model" that accurately simulates wind turbine blade geometry, incorporating energy dissipation effects (radiation damping) evaluated via thin-layer element methods.

The technologies established in this project serve as foundational solutions applicable to future offshore wind developments in Japan's general sea areas, particularly those involving heterogeneous seabeds with bedrock and deep waters. As an engineering company with comprehensive high-level expertise in the design, fabrication, and construction of offshore wind foundations, the Company will continue contributing to the realization of a decarbonized society.

※1 Group II Awarded to organizations involved in groundbreaking projects that have made significant contributions to the advancement of civil engineering technology and societal development.

※2 Jacket Foundation A jacket foundation is a foundation structure where a three-dimensional truss structure made of steel pipes (called a jacket) is fixed to the seabed or ground using driven piles. Named for its jacket-like (outerwear) structure that covers the piles, it is primarily used in offshore wind farms and offshore oil platforms.

※3 Three Pile Installation Methods Three pile installation methods (All-Casing Method, RS Plus® Method, and Impact Driving Method) are applied according to ground conditions (medium-hard rock, soft rock, and sedimentary layers).

※4 Radiation Damping Evaluation The effect of structural vibration energy propagating and dissipating into the surrounding ground (radiation damping) is evaluated using the thin-layer element method.