Block Island Jackets Go Under Investigation

A team led by the Rhode Island Coastal Resources Management Council (CRMC) is set to conduct a research project on the engineering of the jacket foundations at the U.S. Block Island offshore wind farm.

The U.S. Bureau of Safety and Environmental Enforcement (BSEE) has awarded USD 608,722 for the 28-month study of the first U.S. offshore wind commercial project.

CRMC will be overseeing the study in cooperation with the University of Rhode Island’s (URI) Ocean and Civil Engineering Departments, Tufts University and the Norwegian Geotechnical Institute (NGI).

The team will first develop a suite of sensors to be affixed to the turbines and measurements of accelerations at different turbine locations will be taken to determine the resonant frequencies and soil damping.

Stresses and bending moments will be determined at different locations on the turbine structure, including at the tower and jacket interface, with possible tilt of the jackets from foundation soil displacement also measured.

In addition, the study will assess the actual fatigue of the overall structure by analyzing cyclical stress and strain on the structure versus design assumptions.

The sensor systems will be developed beginning in May, after which Ørsted, the wind farm owner, will install a temporary data collection system to help determine the best placement for the sensors that will be deployed for an entire season.

Monitoring will begin in May 2020 with the project expected to be completed in December 2021.

The study is said to be due to a gap in the industry knowledge base on the design and operation of offshore wind infrastructure in the Atlantic.

Data is expected to assist BSEE, BOEM and CRMC to develop regulatory standards and industry recommendations for the U.S. industry, with the results applicable for projects worldwide.

“The study aims to verify that these structures as engineered and installed will meet or exceed their 30 to 35-year design life,” said David Ciochetto, a CRMC ocean engineer and manager for the project.

“The team is making the sensors robust – it’s a very harsh environment. Like the wind farm, the team’s sensors and data communication networks will be exposed to the salt spray, wind, sun and possibly the larger waves for an entire season. Cables will need to be attached to the large structure to connect the various sensors to a computer system recording the data and transferring it to shore.”

Photo: CRMC